1 /*
2 * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/classLoader.hpp"
27 #include "classfile/javaClasses.hpp"
28 #include "classfile/moduleEntry.hpp"
29 #include "classfile/systemDictionary.hpp"
30 #include "classfile/vmSymbols.hpp"
31 #include "code/codeCache.hpp"
32 #include "code/scopeDesc.hpp"
33 #include "compiler/compileBroker.hpp"
34 #include "compiler/compileTask.hpp"
35 #include "gc/shared/gcId.hpp"
36 #include "gc/shared/gcLocker.inline.hpp"
37 #include "gc/shared/workgroup.hpp"
38 #include "interpreter/interpreter.hpp"
39 #include "interpreter/linkResolver.hpp"
40 #include "interpreter/oopMapCache.hpp"
41 #include "jvmtifiles/jvmtiEnv.hpp"
42 #include "logging/log.hpp"
43 #include "logging/logConfiguration.hpp"
44 #include "memory/metaspaceShared.hpp"
45 #include "memory/oopFactory.hpp"
46 #include "memory/resourceArea.hpp"
47 #include "memory/universe.inline.hpp"
48 #include "oops/instanceKlass.hpp"
49 #include "oops/objArrayOop.hpp"
50 #include "oops/oop.inline.hpp"
51 #include "oops/symbol.hpp"
52 #include "oops/verifyOopClosure.hpp"
53 #include "prims/jvm_misc.hpp"
54 #include "prims/jvmtiExport.hpp"
55 #include "prims/jvmtiThreadState.hpp"
56 #include "prims/privilegedStack.hpp"
57 #include "runtime/arguments.hpp"
58 #include "runtime/atomic.hpp"
59 #include "runtime/biasedLocking.hpp"
60 #include "runtime/commandLineFlagConstraintList.hpp"
61 #include "runtime/commandLineFlagWriteableList.hpp"
62 #include "runtime/commandLineFlagRangeList.hpp"
63 #include "runtime/deoptimization.hpp"
64 #include "runtime/fprofiler.hpp"
65 #include "runtime/frame.inline.hpp"
66 #include "runtime/globals.hpp"
67 #include "runtime/init.hpp"
68 #include "runtime/interfaceSupport.hpp"
69 #include "runtime/java.hpp"
70 #include "runtime/javaCalls.hpp"
71 #include "runtime/jniPeriodicChecker.hpp"
72 #include "runtime/timerTrace.hpp"
73 #include "runtime/memprofiler.hpp"
74 #include "runtime/mutexLocker.hpp"
75 #include "runtime/objectMonitor.hpp"
76 #include "runtime/orderAccess.inline.hpp"
77 #include "runtime/osThread.hpp"
78 #include "runtime/safepoint.hpp"
79 #include "runtime/sharedRuntime.hpp"
80 #include "runtime/statSampler.hpp"
81 #include "runtime/stubRoutines.hpp"
82 #include "runtime/sweeper.hpp"
83 #include "runtime/task.hpp"
84 #include "runtime/thread.inline.hpp"
85 #include "runtime/threadCritical.hpp"
86 #include "runtime/vframe.hpp"
87 #include "runtime/vframeArray.hpp"
88 #include "runtime/vframe_hp.hpp"
89 #include "runtime/vmThread.hpp"
90 #include "runtime/vm_operations.hpp"
91 #include "runtime/vm_version.hpp"
92 #include "services/attachListener.hpp"
93 #include "services/management.hpp"
94 #include "services/memTracker.hpp"
95 #include "services/threadService.hpp"
96 #include "trace/traceMacros.hpp"
97 #include "trace/tracing.hpp"
98 #include "utilities/defaultStream.hpp"
99 #include "utilities/dtrace.hpp"
100 #include "utilities/events.hpp"
101 #include "utilities/macros.hpp"
102 #include "utilities/preserveException.hpp"
103 #if INCLUDE_ALL_GCS
104 #include "gc/cms/concurrentMarkSweepThread.hpp"
105 #include "gc/g1/concurrentMarkThread.inline.hpp"
106 #include "gc/parallel/pcTasks.hpp"
107 #endif // INCLUDE_ALL_GCS
108 #if INCLUDE_JVMCI
109 #include "jvmci/jvmciCompiler.hpp"
110 #include "jvmci/jvmciRuntime.hpp"
111 #endif
112 #ifdef COMPILER1
113 #include "c1/c1_Compiler.hpp"
114 #endif
115 #ifdef COMPILER2
116 #include "opto/c2compiler.hpp"
117 #include "opto/idealGraphPrinter.hpp"
118 #endif
119 #if INCLUDE_RTM_OPT
120 #include "runtime/rtmLocking.hpp"
121 #endif
122
123 // Initialization after module runtime initialization
124 void universe_post_module_init(); // must happen after call_initPhase2
125
126 #ifdef DTRACE_ENABLED
127
128 // Only bother with this argument setup if dtrace is available
129
130 #define HOTSPOT_THREAD_PROBE_start HOTSPOT_THREAD_START
131 #define HOTSPOT_THREAD_PROBE_stop HOTSPOT_THREAD_STOP
132
133 #define DTRACE_THREAD_PROBE(probe, javathread) \
134 { \
135 ResourceMark rm(this); \
136 int len = 0; \
137 const char* name = (javathread)->get_thread_name(); \
138 len = strlen(name); \
139 HOTSPOT_THREAD_PROBE_##probe(/* probe = start, stop */ \
140 (char *) name, len, \
141 java_lang_Thread::thread_id((javathread)->threadObj()), \
142 (uintptr_t) (javathread)->osthread()->thread_id(), \
143 java_lang_Thread::is_daemon((javathread)->threadObj())); \
144 }
145
146 #else // ndef DTRACE_ENABLED
147
148 #define DTRACE_THREAD_PROBE(probe, javathread)
149
150 #endif // ndef DTRACE_ENABLED
151
152 #ifndef USE_LIBRARY_BASED_TLS_ONLY
153 // Current thread is maintained as a thread-local variable
154 THREAD_LOCAL_DECL Thread* Thread::_thr_current = NULL;
155 #endif
156 // Class hierarchy
157 // - Thread
158 // - VMThread
159 // - WatcherThread
160 // - ConcurrentMarkSweepThread
161 // - JavaThread
162 // - CompilerThread
163
164 // ======= Thread ========
165 // Support for forcing alignment of thread objects for biased locking
166 void* Thread::allocate(size_t size, bool throw_excpt, MEMFLAGS flags) {
167 if (UseBiasedLocking) {
168 const int alignment = markOopDesc::biased_lock_alignment;
169 size_t aligned_size = size + (alignment - sizeof(intptr_t));
170 void* real_malloc_addr = throw_excpt? AllocateHeap(aligned_size, flags, CURRENT_PC)
171 : AllocateHeap(aligned_size, flags, CURRENT_PC,
172 AllocFailStrategy::RETURN_NULL);
173 void* aligned_addr = (void*) align_size_up((intptr_t) real_malloc_addr, alignment);
174 assert(((uintptr_t) aligned_addr + (uintptr_t) size) <=
175 ((uintptr_t) real_malloc_addr + (uintptr_t) aligned_size),
176 "JavaThread alignment code overflowed allocated storage");
177 if (aligned_addr != real_malloc_addr) {
178 log_info(biasedlocking)("Aligned thread " INTPTR_FORMAT " to " INTPTR_FORMAT,
179 p2i(real_malloc_addr),
180 p2i(aligned_addr));
181 }
182 ((Thread*) aligned_addr)->_real_malloc_address = real_malloc_addr;
183 return aligned_addr;
184 } else {
185 return throw_excpt? AllocateHeap(size, flags, CURRENT_PC)
186 : AllocateHeap(size, flags, CURRENT_PC, AllocFailStrategy::RETURN_NULL);
187 }
188 }
189
190 void Thread::operator delete(void* p) {
191 if (UseBiasedLocking) {
192 void* real_malloc_addr = ((Thread*) p)->_real_malloc_address;
193 FreeHeap(real_malloc_addr);
194 } else {
195 FreeHeap(p);
196 }
197 }
198
199
200 // Base class for all threads: VMThread, WatcherThread, ConcurrentMarkSweepThread,
201 // JavaThread
202
203
204 Thread::Thread() {
205 // stack and get_thread
206 set_stack_base(NULL);
207 set_stack_size(0);
208 set_self_raw_id(0);
209 set_lgrp_id(-1);
210 DEBUG_ONLY(clear_suspendible_thread();)
211
212 // allocated data structures
213 set_osthread(NULL);
214 set_resource_area(new (mtThread)ResourceArea());
215 DEBUG_ONLY(_current_resource_mark = NULL;)
216 set_handle_area(new (mtThread) HandleArea(NULL));
217 set_metadata_handles(new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(30, true));
218 set_active_handles(NULL);
219 set_free_handle_block(NULL);
220 set_last_handle_mark(NULL);
221
222 // This initial value ==> never claimed.
223 _oops_do_parity = 0;
224
225 // the handle mark links itself to last_handle_mark
226 new HandleMark(this);
227
228 // plain initialization
229 debug_only(_owned_locks = NULL;)
230 debug_only(_allow_allocation_count = 0;)
231 NOT_PRODUCT(_allow_safepoint_count = 0;)
232 NOT_PRODUCT(_skip_gcalot = false;)
233 _jvmti_env_iteration_count = 0;
234 set_allocated_bytes(0);
235 _vm_operation_started_count = 0;
236 _vm_operation_completed_count = 0;
237 _current_pending_monitor = NULL;
238 _current_pending_monitor_is_from_java = true;
239 _current_waiting_monitor = NULL;
240 _num_nested_signal = 0;
241 omFreeList = NULL;
242 omFreeCount = 0;
243 omFreeProvision = 32;
244 omInUseList = NULL;
245 omInUseCount = 0;
246
247 #ifdef ASSERT
248 _visited_for_critical_count = false;
249 #endif
250
251 _SR_lock = new Monitor(Mutex::suspend_resume, "SR_lock", true,
252 Monitor::_safepoint_check_sometimes);
253 _suspend_flags = 0;
254
255 // thread-specific hashCode stream generator state - Marsaglia shift-xor form
256 _hashStateX = os::random();
257 _hashStateY = 842502087;
258 _hashStateZ = 0x8767; // (int)(3579807591LL & 0xffff) ;
259 _hashStateW = 273326509;
260
261 _OnTrap = 0;
262 _schedctl = NULL;
263 _Stalled = 0;
264 _TypeTag = 0x2BAD;
265
266 // Many of the following fields are effectively final - immutable
267 // Note that nascent threads can't use the Native Monitor-Mutex
268 // construct until the _MutexEvent is initialized ...
269 // CONSIDER: instead of using a fixed set of purpose-dedicated ParkEvents
270 // we might instead use a stack of ParkEvents that we could provision on-demand.
271 // The stack would act as a cache to avoid calls to ParkEvent::Allocate()
272 // and ::Release()
273 _ParkEvent = ParkEvent::Allocate(this);
274 _SleepEvent = ParkEvent::Allocate(this);
275 _MutexEvent = ParkEvent::Allocate(this);
276 _MuxEvent = ParkEvent::Allocate(this);
277
278 #ifdef CHECK_UNHANDLED_OOPS
279 if (CheckUnhandledOops) {
280 _unhandled_oops = new UnhandledOops(this);
281 }
282 #endif // CHECK_UNHANDLED_OOPS
283 #ifdef ASSERT
284 if (UseBiasedLocking) {
285 assert((((uintptr_t) this) & (markOopDesc::biased_lock_alignment - 1)) == 0, "forced alignment of thread object failed");
286 assert(this == _real_malloc_address ||
287 this == (void*) align_size_up((intptr_t) _real_malloc_address, markOopDesc::biased_lock_alignment),
288 "bug in forced alignment of thread objects");
289 }
290 #endif // ASSERT
291 }
292
293 void Thread::initialize_thread_current() {
294 #ifndef USE_LIBRARY_BASED_TLS_ONLY
295 assert(_thr_current == NULL, "Thread::current already initialized");
296 _thr_current = this;
297 #endif
298 assert(ThreadLocalStorage::thread() == NULL, "ThreadLocalStorage::thread already initialized");
299 ThreadLocalStorage::set_thread(this);
300 assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
301 }
302
303 void Thread::clear_thread_current() {
304 assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
305 #ifndef USE_LIBRARY_BASED_TLS_ONLY
306 _thr_current = NULL;
307 #endif
308 ThreadLocalStorage::set_thread(NULL);
309 }
310
311 void Thread::record_stack_base_and_size() {
312 set_stack_base(os::current_stack_base());
313 set_stack_size(os::current_stack_size());
314 // CR 7190089: on Solaris, primordial thread's stack is adjusted
315 // in initialize_thread(). Without the adjustment, stack size is
316 // incorrect if stack is set to unlimited (ulimit -s unlimited).
317 // So far, only Solaris has real implementation of initialize_thread().
318 //
319 // set up any platform-specific state.
320 os::initialize_thread(this);
321
322 // Set stack limits after thread is initialized.
323 if (is_Java_thread()) {
324 ((JavaThread*) this)->set_stack_overflow_limit();
325 ((JavaThread*) this)->set_reserved_stack_activation(stack_base());
326 }
327 #if INCLUDE_NMT
328 // record thread's native stack, stack grows downward
329 MemTracker::record_thread_stack(stack_end(), stack_size());
330 #endif // INCLUDE_NMT
331 log_debug(os, thread)("Thread " UINTX_FORMAT " stack dimensions: "
332 PTR_FORMAT "-" PTR_FORMAT " (" SIZE_FORMAT "k).",
333 os::current_thread_id(), p2i(stack_base() - stack_size()),
334 p2i(stack_base()), stack_size()/1024);
335 }
336
337
338 Thread::~Thread() {
339 EVENT_THREAD_DESTRUCT(this);
340
341 // stack_base can be NULL if the thread is never started or exited before
342 // record_stack_base_and_size called. Although, we would like to ensure
343 // that all started threads do call record_stack_base_and_size(), there is
344 // not proper way to enforce that.
345 #if INCLUDE_NMT
346 if (_stack_base != NULL) {
347 MemTracker::release_thread_stack(stack_end(), stack_size());
348 #ifdef ASSERT
349 set_stack_base(NULL);
350 #endif
351 }
352 #endif // INCLUDE_NMT
353
354 // deallocate data structures
355 delete resource_area();
356 // since the handle marks are using the handle area, we have to deallocated the root
357 // handle mark before deallocating the thread's handle area,
358 assert(last_handle_mark() != NULL, "check we have an element");
359 delete last_handle_mark();
360 assert(last_handle_mark() == NULL, "check we have reached the end");
361
362 // It's possible we can encounter a null _ParkEvent, etc., in stillborn threads.
363 // We NULL out the fields for good hygiene.
364 ParkEvent::Release(_ParkEvent); _ParkEvent = NULL;
365 ParkEvent::Release(_SleepEvent); _SleepEvent = NULL;
366 ParkEvent::Release(_MutexEvent); _MutexEvent = NULL;
367 ParkEvent::Release(_MuxEvent); _MuxEvent = NULL;
368
369 delete handle_area();
370 delete metadata_handles();
371
372 // SR_handler uses this as a termination indicator -
373 // needs to happen before os::free_thread()
374 delete _SR_lock;
375 _SR_lock = NULL;
376
377 // osthread() can be NULL, if creation of thread failed.
378 if (osthread() != NULL) os::free_thread(osthread());
379
380 // clear Thread::current if thread is deleting itself.
381 // Needed to ensure JNI correctly detects non-attached threads.
382 if (this == Thread::current()) {
383 clear_thread_current();
384 }
385
386 CHECK_UNHANDLED_OOPS_ONLY(if (CheckUnhandledOops) delete unhandled_oops();)
387 }
388
389 // NOTE: dummy function for assertion purpose.
390 void Thread::run() {
391 ShouldNotReachHere();
392 }
393
394 #ifdef ASSERT
395 // Private method to check for dangling thread pointer
396 void check_for_dangling_thread_pointer(Thread *thread) {
397 assert(!thread->is_Java_thread() || Thread::current() == thread || Threads_lock->owned_by_self(),
398 "possibility of dangling Thread pointer");
399 }
400 #endif
401
402 ThreadPriority Thread::get_priority(const Thread* const thread) {
403 ThreadPriority priority;
404 // Can return an error!
405 (void)os::get_priority(thread, priority);
406 assert(MinPriority <= priority && priority <= MaxPriority, "non-Java priority found");
407 return priority;
408 }
409
410 void Thread::set_priority(Thread* thread, ThreadPriority priority) {
411 debug_only(check_for_dangling_thread_pointer(thread);)
412 // Can return an error!
413 (void)os::set_priority(thread, priority);
414 }
415
416
417 void Thread::start(Thread* thread) {
418 // Start is different from resume in that its safety is guaranteed by context or
419 // being called from a Java method synchronized on the Thread object.
420 if (!DisableStartThread) {
421 if (thread->is_Java_thread()) {
422 // Initialize the thread state to RUNNABLE before starting this thread.
423 // Can not set it after the thread started because we do not know the
424 // exact thread state at that time. It could be in MONITOR_WAIT or
425 // in SLEEPING or some other state.
426 java_lang_Thread::set_thread_status(((JavaThread*)thread)->threadObj(),
427 java_lang_Thread::RUNNABLE);
428 }
429 os::start_thread(thread);
430 }
431 }
432
433 // Enqueue a VM_Operation to do the job for us - sometime later
434 void Thread::send_async_exception(oop java_thread, oop java_throwable) {
435 VM_ThreadStop* vm_stop = new VM_ThreadStop(java_thread, java_throwable);
436 VMThread::execute(vm_stop);
437 }
438
439
440 // Check if an external suspend request has completed (or has been
441 // cancelled). Returns true if the thread is externally suspended and
442 // false otherwise.
443 //
444 // The bits parameter returns information about the code path through
445 // the routine. Useful for debugging:
446 //
447 // set in is_ext_suspend_completed():
448 // 0x00000001 - routine was entered
449 // 0x00000010 - routine return false at end
450 // 0x00000100 - thread exited (return false)
451 // 0x00000200 - suspend request cancelled (return false)
452 // 0x00000400 - thread suspended (return true)
453 // 0x00001000 - thread is in a suspend equivalent state (return true)
454 // 0x00002000 - thread is native and walkable (return true)
455 // 0x00004000 - thread is native_trans and walkable (needed retry)
456 //
457 // set in wait_for_ext_suspend_completion():
458 // 0x00010000 - routine was entered
459 // 0x00020000 - suspend request cancelled before loop (return false)
460 // 0x00040000 - thread suspended before loop (return true)
461 // 0x00080000 - suspend request cancelled in loop (return false)
462 // 0x00100000 - thread suspended in loop (return true)
463 // 0x00200000 - suspend not completed during retry loop (return false)
464
465 // Helper class for tracing suspend wait debug bits.
466 //
467 // 0x00000100 indicates that the target thread exited before it could
468 // self-suspend which is not a wait failure. 0x00000200, 0x00020000 and
469 // 0x00080000 each indicate a cancelled suspend request so they don't
470 // count as wait failures either.
471 #define DEBUG_FALSE_BITS (0x00000010 | 0x00200000)
472
473 class TraceSuspendDebugBits : public StackObj {
474 private:
475 JavaThread * jt;
476 bool is_wait;
477 bool called_by_wait; // meaningful when !is_wait
478 uint32_t * bits;
479
480 public:
481 TraceSuspendDebugBits(JavaThread *_jt, bool _is_wait, bool _called_by_wait,
482 uint32_t *_bits) {
483 jt = _jt;
484 is_wait = _is_wait;
485 called_by_wait = _called_by_wait;
486 bits = _bits;
487 }
488
489 ~TraceSuspendDebugBits() {
490 if (!is_wait) {
491 #if 1
492 // By default, don't trace bits for is_ext_suspend_completed() calls.
493 // That trace is very chatty.
494 return;
495 #else
496 if (!called_by_wait) {
497 // If tracing for is_ext_suspend_completed() is enabled, then only
498 // trace calls to it from wait_for_ext_suspend_completion()
499 return;
500 }
501 #endif
502 }
503
504 if (AssertOnSuspendWaitFailure || TraceSuspendWaitFailures) {
505 if (bits != NULL && (*bits & DEBUG_FALSE_BITS) != 0) {
506 MutexLocker ml(Threads_lock); // needed for get_thread_name()
507 ResourceMark rm;
508
509 tty->print_cr(
510 "Failed wait_for_ext_suspend_completion(thread=%s, debug_bits=%x)",
511 jt->get_thread_name(), *bits);
512
513 guarantee(!AssertOnSuspendWaitFailure, "external suspend wait failed");
514 }
515 }
516 }
517 };
518 #undef DEBUG_FALSE_BITS
519
520
521 bool JavaThread::is_ext_suspend_completed(bool called_by_wait, int delay,
522 uint32_t *bits) {
523 TraceSuspendDebugBits tsdb(this, false /* !is_wait */, called_by_wait, bits);
524
525 bool did_trans_retry = false; // only do thread_in_native_trans retry once
526 bool do_trans_retry; // flag to force the retry
527
528 *bits |= 0x00000001;
529
530 do {
531 do_trans_retry = false;
532
533 if (is_exiting()) {
534 // Thread is in the process of exiting. This is always checked
535 // first to reduce the risk of dereferencing a freed JavaThread.
536 *bits |= 0x00000100;
537 return false;
538 }
539
540 if (!is_external_suspend()) {
541 // Suspend request is cancelled. This is always checked before
542 // is_ext_suspended() to reduce the risk of a rogue resume
543 // confusing the thread that made the suspend request.
544 *bits |= 0x00000200;
545 return false;
546 }
547
548 if (is_ext_suspended()) {
549 // thread is suspended
550 *bits |= 0x00000400;
551 return true;
552 }
553
554 // Now that we no longer do hard suspends of threads running
555 // native code, the target thread can be changing thread state
556 // while we are in this routine:
557 //
558 // _thread_in_native -> _thread_in_native_trans -> _thread_blocked
559 //
560 // We save a copy of the thread state as observed at this moment
561 // and make our decision about suspend completeness based on the
562 // copy. This closes the race where the thread state is seen as
563 // _thread_in_native_trans in the if-thread_blocked check, but is
564 // seen as _thread_blocked in if-thread_in_native_trans check.
565 JavaThreadState save_state = thread_state();
566
567 if (save_state == _thread_blocked && is_suspend_equivalent()) {
568 // If the thread's state is _thread_blocked and this blocking
569 // condition is known to be equivalent to a suspend, then we can
570 // consider the thread to be externally suspended. This means that
571 // the code that sets _thread_blocked has been modified to do
572 // self-suspension if the blocking condition releases. We also
573 // used to check for CONDVAR_WAIT here, but that is now covered by
574 // the _thread_blocked with self-suspension check.
575 //
576 // Return true since we wouldn't be here unless there was still an
577 // external suspend request.
578 *bits |= 0x00001000;
579 return true;
580 } else if (save_state == _thread_in_native && frame_anchor()->walkable()) {
581 // Threads running native code will self-suspend on native==>VM/Java
582 // transitions. If its stack is walkable (should always be the case
583 // unless this function is called before the actual java_suspend()
584 // call), then the wait is done.
585 *bits |= 0x00002000;
586 return true;
587 } else if (!called_by_wait && !did_trans_retry &&
588 save_state == _thread_in_native_trans &&
589 frame_anchor()->walkable()) {
590 // The thread is transitioning from thread_in_native to another
591 // thread state. check_safepoint_and_suspend_for_native_trans()
592 // will force the thread to self-suspend. If it hasn't gotten
593 // there yet we may have caught the thread in-between the native
594 // code check above and the self-suspend. Lucky us. If we were
595 // called by wait_for_ext_suspend_completion(), then it
596 // will be doing the retries so we don't have to.
597 //
598 // Since we use the saved thread state in the if-statement above,
599 // there is a chance that the thread has already transitioned to
600 // _thread_blocked by the time we get here. In that case, we will
601 // make a single unnecessary pass through the logic below. This
602 // doesn't hurt anything since we still do the trans retry.
603
604 *bits |= 0x00004000;
605
606 // Once the thread leaves thread_in_native_trans for another
607 // thread state, we break out of this retry loop. We shouldn't
608 // need this flag to prevent us from getting back here, but
609 // sometimes paranoia is good.
610 did_trans_retry = true;
611
612 // We wait for the thread to transition to a more usable state.
613 for (int i = 1; i <= SuspendRetryCount; i++) {
614 // We used to do an "os::yield_all(i)" call here with the intention
615 // that yielding would increase on each retry. However, the parameter
616 // is ignored on Linux which means the yield didn't scale up. Waiting
617 // on the SR_lock below provides a much more predictable scale up for
618 // the delay. It also provides a simple/direct point to check for any
619 // safepoint requests from the VMThread
620
621 // temporarily drops SR_lock while doing wait with safepoint check
622 // (if we're a JavaThread - the WatcherThread can also call this)
623 // and increase delay with each retry
624 SR_lock()->wait(!Thread::current()->is_Java_thread(), i * delay);
625
626 // check the actual thread state instead of what we saved above
627 if (thread_state() != _thread_in_native_trans) {
628 // the thread has transitioned to another thread state so
629 // try all the checks (except this one) one more time.
630 do_trans_retry = true;
631 break;
632 }
633 } // end retry loop
634
635
636 }
637 } while (do_trans_retry);
638
639 *bits |= 0x00000010;
640 return false;
641 }
642
643 // Wait for an external suspend request to complete (or be cancelled).
644 // Returns true if the thread is externally suspended and false otherwise.
645 //
646 bool JavaThread::wait_for_ext_suspend_completion(int retries, int delay,
647 uint32_t *bits) {
648 TraceSuspendDebugBits tsdb(this, true /* is_wait */,
649 false /* !called_by_wait */, bits);
650
651 // local flag copies to minimize SR_lock hold time
652 bool is_suspended;
653 bool pending;
654 uint32_t reset_bits;
655
656 // set a marker so is_ext_suspend_completed() knows we are the caller
657 *bits |= 0x00010000;
658
659 // We use reset_bits to reinitialize the bits value at the top of
660 // each retry loop. This allows the caller to make use of any
661 // unused bits for their own marking purposes.
662 reset_bits = *bits;
663
664 {
665 MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
666 is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
667 delay, bits);
668 pending = is_external_suspend();
669 }
670 // must release SR_lock to allow suspension to complete
671
672 if (!pending) {
673 // A cancelled suspend request is the only false return from
674 // is_ext_suspend_completed() that keeps us from entering the
675 // retry loop.
676 *bits |= 0x00020000;
677 return false;
678 }
679
680 if (is_suspended) {
681 *bits |= 0x00040000;
682 return true;
683 }
684
685 for (int i = 1; i <= retries; i++) {
686 *bits = reset_bits; // reinit to only track last retry
687
688 // We used to do an "os::yield_all(i)" call here with the intention
689 // that yielding would increase on each retry. However, the parameter
690 // is ignored on Linux which means the yield didn't scale up. Waiting
691 // on the SR_lock below provides a much more predictable scale up for
692 // the delay. It also provides a simple/direct point to check for any
693 // safepoint requests from the VMThread
694
695 {
696 MutexLocker ml(SR_lock());
697 // wait with safepoint check (if we're a JavaThread - the WatcherThread
698 // can also call this) and increase delay with each retry
699 SR_lock()->wait(!Thread::current()->is_Java_thread(), i * delay);
700
701 is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
702 delay, bits);
703
704 // It is possible for the external suspend request to be cancelled
705 // (by a resume) before the actual suspend operation is completed.
706 // Refresh our local copy to see if we still need to wait.
707 pending = is_external_suspend();
708 }
709
710 if (!pending) {
711 // A cancelled suspend request is the only false return from
712 // is_ext_suspend_completed() that keeps us from staying in the
713 // retry loop.
714 *bits |= 0x00080000;
715 return false;
716 }
717
718 if (is_suspended) {
719 *bits |= 0x00100000;
720 return true;
721 }
722 } // end retry loop
723
724 // thread did not suspend after all our retries
725 *bits |= 0x00200000;
726 return false;
727 }
728
729 #ifndef PRODUCT
730 void JavaThread::record_jump(address target, address instr, const char* file,
731 int line) {
732
733 // This should not need to be atomic as the only way for simultaneous
734 // updates is via interrupts. Even then this should be rare or non-existent
735 // and we don't care that much anyway.
736
737 int index = _jmp_ring_index;
738 _jmp_ring_index = (index + 1) & (jump_ring_buffer_size - 1);
739 _jmp_ring[index]._target = (intptr_t) target;
740 _jmp_ring[index]._instruction = (intptr_t) instr;
741 _jmp_ring[index]._file = file;
742 _jmp_ring[index]._line = line;
743 }
744 #endif // PRODUCT
745
746 // Called by flat profiler
747 // Callers have already called wait_for_ext_suspend_completion
748 // The assertion for that is currently too complex to put here:
749 bool JavaThread::profile_last_Java_frame(frame* _fr) {
750 bool gotframe = false;
751 // self suspension saves needed state.
752 if (has_last_Java_frame() && _anchor.walkable()) {
753 *_fr = pd_last_frame();
754 gotframe = true;
755 }
756 return gotframe;
757 }
758
759 void Thread::interrupt(Thread* thread) {
760 debug_only(check_for_dangling_thread_pointer(thread);)
761 os::interrupt(thread);
762 }
763
764 bool Thread::is_interrupted(Thread* thread, bool clear_interrupted) {
765 debug_only(check_for_dangling_thread_pointer(thread);)
766 // Note: If clear_interrupted==false, this simply fetches and
767 // returns the value of the field osthread()->interrupted().
768 return os::is_interrupted(thread, clear_interrupted);
769 }
770
771
772 // GC Support
773 bool Thread::claim_oops_do_par_case(int strong_roots_parity) {
774 jint thread_parity = _oops_do_parity;
775 if (thread_parity != strong_roots_parity) {
776 jint res = Atomic::cmpxchg(strong_roots_parity, &_oops_do_parity, thread_parity);
777 if (res == thread_parity) {
778 return true;
779 } else {
780 guarantee(res == strong_roots_parity, "Or else what?");
781 return false;
782 }
783 }
784 return false;
785 }
786
787 void Thread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
788 active_handles()->oops_do(f);
789 // Do oop for ThreadShadow
790 f->do_oop((oop*)&_pending_exception);
791 handle_area()->oops_do(f);
792
793 if (MonitorInUseLists) {
794 // When using thread local monitor lists, we scan them here,
795 // and the remaining global monitors in ObjectSynchronizer::oops_do().
796 ObjectSynchronizer::thread_local_used_oops_do(this, f);
797 }
798 }
799
800 void Thread::metadata_handles_do(void f(Metadata*)) {
801 // Only walk the Handles in Thread.
802 if (metadata_handles() != NULL) {
803 for (int i = 0; i< metadata_handles()->length(); i++) {
804 f(metadata_handles()->at(i));
805 }
806 }
807 }
808
809 void Thread::print_on(outputStream* st) const {
810 // get_priority assumes osthread initialized
811 if (osthread() != NULL) {
812 int os_prio;
813 if (os::get_native_priority(this, &os_prio) == OS_OK) {
814 st->print("os_prio=%d ", os_prio);
815 }
816 st->print("tid=" INTPTR_FORMAT " ", p2i(this));
817 ext().print_on(st);
818 osthread()->print_on(st);
819 }
820 debug_only(if (WizardMode) print_owned_locks_on(st);)
821 }
822
823 // Thread::print_on_error() is called by fatal error handler. Don't use
824 // any lock or allocate memory.
825 void Thread::print_on_error(outputStream* st, char* buf, int buflen) const {
826 assert(!(is_Compiler_thread() || is_Java_thread()), "Can't call name() here if it allocates");
827
828 if (is_VM_thread()) { st->print("VMThread"); }
829 else if (is_GC_task_thread()) { st->print("GCTaskThread"); }
830 else if (is_Watcher_thread()) { st->print("WatcherThread"); }
831 else if (is_ConcurrentGC_thread()) { st->print("ConcurrentGCThread"); }
832 else { st->print("Thread"); }
833
834 if (is_Named_thread()) {
835 st->print(" \"%s\"", name());
836 }
837
838 st->print(" [stack: " PTR_FORMAT "," PTR_FORMAT "]",
839 p2i(stack_end()), p2i(stack_base()));
840
841 if (osthread()) {
842 st->print(" [id=%d]", osthread()->thread_id());
843 }
844 }
845
846 #ifdef ASSERT
847 void Thread::print_owned_locks_on(outputStream* st) const {
848 Monitor *cur = _owned_locks;
849 if (cur == NULL) {
850 st->print(" (no locks) ");
851 } else {
852 st->print_cr(" Locks owned:");
853 while (cur) {
854 cur->print_on(st);
855 cur = cur->next();
856 }
857 }
858 }
859
860 static int ref_use_count = 0;
861
862 bool Thread::owns_locks_but_compiled_lock() const {
863 for (Monitor *cur = _owned_locks; cur; cur = cur->next()) {
864 if (cur != Compile_lock) return true;
865 }
866 return false;
867 }
868
869
870 #endif
871
872 #ifndef PRODUCT
873
874 // The flag: potential_vm_operation notifies if this particular safepoint state could potential
875 // invoke the vm-thread (i.e., and oop allocation). In that case, we also have to make sure that
876 // no threads which allow_vm_block's are held
877 void Thread::check_for_valid_safepoint_state(bool potential_vm_operation) {
878 // Check if current thread is allowed to block at a safepoint
879 if (!(_allow_safepoint_count == 0)) {
880 fatal("Possible safepoint reached by thread that does not allow it");
881 }
882 if (is_Java_thread() && ((JavaThread*)this)->thread_state() != _thread_in_vm) {
883 fatal("LEAF method calling lock?");
884 }
885
886 #ifdef ASSERT
887 if (potential_vm_operation && is_Java_thread()
888 && !Universe::is_bootstrapping()) {
889 // Make sure we do not hold any locks that the VM thread also uses.
890 // This could potentially lead to deadlocks
891 for (Monitor *cur = _owned_locks; cur; cur = cur->next()) {
892 // Threads_lock is special, since the safepoint synchronization will not start before this is
893 // acquired. Hence, a JavaThread cannot be holding it at a safepoint. So is VMOperationRequest_lock,
894 // since it is used to transfer control between JavaThreads and the VMThread
895 // Do not *exclude* any locks unless you are absolutely sure it is correct. Ask someone else first!
896 if ((cur->allow_vm_block() &&
897 cur != Threads_lock &&
898 cur != Compile_lock && // Temporary: should not be necessary when we get separate compilation
899 cur != VMOperationRequest_lock &&
900 cur != VMOperationQueue_lock) ||
901 cur->rank() == Mutex::special) {
902 fatal("Thread holding lock at safepoint that vm can block on: %s", cur->name());
903 }
904 }
905 }
906
907 if (GCALotAtAllSafepoints) {
908 // We could enter a safepoint here and thus have a gc
909 InterfaceSupport::check_gc_alot();
910 }
911 #endif
912 }
913 #endif
914
915 bool Thread::is_in_stack(address adr) const {
916 assert(Thread::current() == this, "is_in_stack can only be called from current thread");
917 address end = os::current_stack_pointer();
918 // Allow non Java threads to call this without stack_base
919 if (_stack_base == NULL) return true;
920 if (stack_base() >= adr && adr >= end) return true;
921
922 return false;
923 }
924
925 bool Thread::is_in_usable_stack(address adr) const {
926 size_t stack_guard_size = os::uses_stack_guard_pages() ? JavaThread::stack_guard_zone_size() : 0;
927 size_t usable_stack_size = _stack_size - stack_guard_size;
928
929 return ((adr < stack_base()) && (adr >= stack_base() - usable_stack_size));
930 }
931
932
933 // We had to move these methods here, because vm threads get into ObjectSynchronizer::enter
934 // However, there is a note in JavaThread::is_lock_owned() about the VM threads not being
935 // used for compilation in the future. If that change is made, the need for these methods
936 // should be revisited, and they should be removed if possible.
937
938 bool Thread::is_lock_owned(address adr) const {
939 return on_local_stack(adr);
940 }
941
942 bool Thread::set_as_starting_thread() {
943 // NOTE: this must be called inside the main thread.
944 return os::create_main_thread((JavaThread*)this);
945 }
946
947 static void initialize_class(Symbol* class_name, TRAPS) {
948 Klass* klass = SystemDictionary::resolve_or_fail(class_name, true, CHECK);
949 InstanceKlass::cast(klass)->initialize(CHECK);
950 }
951
952
953 // Creates the initial ThreadGroup
954 static Handle create_initial_thread_group(TRAPS) {
955 Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_ThreadGroup(), true, CHECK_NH);
956 InstanceKlass* ik = InstanceKlass::cast(k);
957
958 Handle system_instance = ik->allocate_instance_handle(CHECK_NH);
959 {
960 JavaValue result(T_VOID);
961 JavaCalls::call_special(&result,
962 system_instance,
963 ik,
964 vmSymbols::object_initializer_name(),
965 vmSymbols::void_method_signature(),
966 CHECK_NH);
967 }
968 Universe::set_system_thread_group(system_instance());
969
970 Handle main_instance = ik->allocate_instance_handle(CHECK_NH);
971 {
972 JavaValue result(T_VOID);
973 Handle string = java_lang_String::create_from_str("main", CHECK_NH);
974 JavaCalls::call_special(&result,
975 main_instance,
976 ik,
977 vmSymbols::object_initializer_name(),
978 vmSymbols::threadgroup_string_void_signature(),
979 system_instance,
980 string,
981 CHECK_NH);
982 }
983 return main_instance;
984 }
985
986 // Creates the initial Thread
987 static oop create_initial_thread(Handle thread_group, JavaThread* thread,
988 TRAPS) {
989 Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(), true, CHECK_NULL);
990 InstanceKlass* ik = InstanceKlass::cast(k);
991 instanceHandle thread_oop = ik->allocate_instance_handle(CHECK_NULL);
992
993 java_lang_Thread::set_thread(thread_oop(), thread);
994 java_lang_Thread::set_priority(thread_oop(), NormPriority);
995 thread->set_threadObj(thread_oop());
996
997 Handle string = java_lang_String::create_from_str("main", CHECK_NULL);
998
999 JavaValue result(T_VOID);
1000 JavaCalls::call_special(&result, thread_oop,
1001 ik,
1002 vmSymbols::object_initializer_name(),
1003 vmSymbols::threadgroup_string_void_signature(),
1004 thread_group,
1005 string,
1006 CHECK_NULL);
1007 return thread_oop();
1008 }
1009
1010 char java_runtime_name[128] = "";
1011 char java_runtime_version[128] = "";
1012
1013 // extract the JRE name from java.lang.VersionProps.java_runtime_name
1014 static const char* get_java_runtime_name(TRAPS) {
1015 Klass* k = SystemDictionary::find(vmSymbols::java_lang_VersionProps(),
1016 Handle(), Handle(), CHECK_AND_CLEAR_NULL);
1017 fieldDescriptor fd;
1018 bool found = k != NULL &&
1019 InstanceKlass::cast(k)->find_local_field(vmSymbols::java_runtime_name_name(),
1020 vmSymbols::string_signature(), &fd);
1021 if (found) {
1022 oop name_oop = k->java_mirror()->obj_field(fd.offset());
1023 if (name_oop == NULL) {
1024 return NULL;
1025 }
1026 const char* name = java_lang_String::as_utf8_string(name_oop,
1027 java_runtime_name,
1028 sizeof(java_runtime_name));
1029 return name;
1030 } else {
1031 return NULL;
1032 }
1033 }
1034
1035 // extract the JRE version from java.lang.VersionProps.java_runtime_version
1036 static const char* get_java_runtime_version(TRAPS) {
1037 Klass* k = SystemDictionary::find(vmSymbols::java_lang_VersionProps(),
1038 Handle(), Handle(), CHECK_AND_CLEAR_NULL);
1039 fieldDescriptor fd;
1040 bool found = k != NULL &&
1041 InstanceKlass::cast(k)->find_local_field(vmSymbols::java_runtime_version_name(),
1042 vmSymbols::string_signature(), &fd);
1043 if (found) {
1044 oop name_oop = k->java_mirror()->obj_field(fd.offset());
1045 if (name_oop == NULL) {
1046 return NULL;
1047 }
1048 const char* name = java_lang_String::as_utf8_string(name_oop,
1049 java_runtime_version,
1050 sizeof(java_runtime_version));
1051 return name;
1052 } else {
1053 return NULL;
1054 }
1055 }
1056
1057 // General purpose hook into Java code, run once when the VM is initialized.
1058 // The Java library method itself may be changed independently from the VM.
1059 static void call_postVMInitHook(TRAPS) {
1060 Klass* klass = SystemDictionary::resolve_or_null(vmSymbols::jdk_internal_vm_PostVMInitHook(), THREAD);
1061 if (klass != NULL) {
1062 JavaValue result(T_VOID);
1063 JavaCalls::call_static(&result, klass, vmSymbols::run_method_name(),
1064 vmSymbols::void_method_signature(),
1065 CHECK);
1066 }
1067 }
1068
1069 static void reset_vm_info_property(TRAPS) {
1070 // the vm info string
1071 ResourceMark rm(THREAD);
1072 const char *vm_info = VM_Version::vm_info_string();
1073
1074 // java.lang.System class
1075 Klass* klass = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
1076
1077 // setProperty arguments
1078 Handle key_str = java_lang_String::create_from_str("java.vm.info", CHECK);
1079 Handle value_str = java_lang_String::create_from_str(vm_info, CHECK);
1080
1081 // return value
1082 JavaValue r(T_OBJECT);
1083
1084 // public static String setProperty(String key, String value);
1085 JavaCalls::call_static(&r,
1086 klass,
1087 vmSymbols::setProperty_name(),
1088 vmSymbols::string_string_string_signature(),
1089 key_str,
1090 value_str,
1091 CHECK);
1092 }
1093
1094
1095 void JavaThread::allocate_threadObj(Handle thread_group, const char* thread_name,
1096 bool daemon, TRAPS) {
1097 assert(thread_group.not_null(), "thread group should be specified");
1098 assert(threadObj() == NULL, "should only create Java thread object once");
1099
1100 Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(), true, CHECK);
1101 InstanceKlass* ik = InstanceKlass::cast(k);
1102 instanceHandle thread_oop = ik->allocate_instance_handle(CHECK);
1103
1104 java_lang_Thread::set_thread(thread_oop(), this);
1105 java_lang_Thread::set_priority(thread_oop(), NormPriority);
1106 set_threadObj(thread_oop());
1107
1108 JavaValue result(T_VOID);
1109 if (thread_name != NULL) {
1110 Handle name = java_lang_String::create_from_str(thread_name, CHECK);
1111 // Thread gets assigned specified name and null target
1112 JavaCalls::call_special(&result,
1113 thread_oop,
1114 ik,
1115 vmSymbols::object_initializer_name(),
1116 vmSymbols::threadgroup_string_void_signature(),
1117 thread_group, // Argument 1
1118 name, // Argument 2
1119 THREAD);
1120 } else {
1121 // Thread gets assigned name "Thread-nnn" and null target
1122 // (java.lang.Thread doesn't have a constructor taking only a ThreadGroup argument)
1123 JavaCalls::call_special(&result,
1124 thread_oop,
1125 ik,
1126 vmSymbols::object_initializer_name(),
1127 vmSymbols::threadgroup_runnable_void_signature(),
1128 thread_group, // Argument 1
1129 Handle(), // Argument 2
1130 THREAD);
1131 }
1132
1133
1134 if (daemon) {
1135 java_lang_Thread::set_daemon(thread_oop());
1136 }
1137
1138 if (HAS_PENDING_EXCEPTION) {
1139 return;
1140 }
1141
1142 Klass* group = SystemDictionary::ThreadGroup_klass();
1143 Handle threadObj(THREAD, this->threadObj());
1144
1145 JavaCalls::call_special(&result,
1146 thread_group,
1147 group,
1148 vmSymbols::add_method_name(),
1149 vmSymbols::thread_void_signature(),
1150 threadObj, // Arg 1
1151 THREAD);
1152 }
1153
1154 // NamedThread -- non-JavaThread subclasses with multiple
1155 // uniquely named instances should derive from this.
1156 NamedThread::NamedThread() : Thread() {
1157 _name = NULL;
1158 _processed_thread = NULL;
1159 _gc_id = GCId::undefined();
1160 }
1161
1162 NamedThread::~NamedThread() {
1163 if (_name != NULL) {
1164 FREE_C_HEAP_ARRAY(char, _name);
1165 _name = NULL;
1166 }
1167 }
1168
1169 void NamedThread::set_name(const char* format, ...) {
1170 guarantee(_name == NULL, "Only get to set name once.");
1171 _name = NEW_C_HEAP_ARRAY(char, max_name_len, mtThread);
1172 guarantee(_name != NULL, "alloc failure");
1173 va_list ap;
1174 va_start(ap, format);
1175 jio_vsnprintf(_name, max_name_len, format, ap);
1176 va_end(ap);
1177 }
1178
1179 void NamedThread::initialize_named_thread() {
1180 set_native_thread_name(name());
1181 }
1182
1183 void NamedThread::print_on(outputStream* st) const {
1184 st->print("\"%s\" ", name());
1185 Thread::print_on(st);
1186 st->cr();
1187 }
1188
1189
1190 // ======= WatcherThread ========
1191
1192 // The watcher thread exists to simulate timer interrupts. It should
1193 // be replaced by an abstraction over whatever native support for
1194 // timer interrupts exists on the platform.
1195
1196 WatcherThread* WatcherThread::_watcher_thread = NULL;
1197 bool WatcherThread::_startable = false;
1198 volatile bool WatcherThread::_should_terminate = false;
1199
1200 WatcherThread::WatcherThread() : Thread(), _crash_protection(NULL) {
1201 assert(watcher_thread() == NULL, "we can only allocate one WatcherThread");
1202 if (os::create_thread(this, os::watcher_thread)) {
1203 _watcher_thread = this;
1204
1205 // Set the watcher thread to the highest OS priority which should not be
1206 // used, unless a Java thread with priority java.lang.Thread.MAX_PRIORITY
1207 // is created. The only normal thread using this priority is the reference
1208 // handler thread, which runs for very short intervals only.
1209 // If the VMThread's priority is not lower than the WatcherThread profiling
1210 // will be inaccurate.
1211 os::set_priority(this, MaxPriority);
1212 if (!DisableStartThread) {
1213 os::start_thread(this);
1214 }
1215 }
1216 }
1217
1218 int WatcherThread::sleep() const {
1219 // The WatcherThread does not participate in the safepoint protocol
1220 // for the PeriodicTask_lock because it is not a JavaThread.
1221 MutexLockerEx ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
1222
1223 if (_should_terminate) {
1224 // check for termination before we do any housekeeping or wait
1225 return 0; // we did not sleep.
1226 }
1227
1228 // remaining will be zero if there are no tasks,
1229 // causing the WatcherThread to sleep until a task is
1230 // enrolled
1231 int remaining = PeriodicTask::time_to_wait();
1232 int time_slept = 0;
1233
1234 // we expect this to timeout - we only ever get unparked when
1235 // we should terminate or when a new task has been enrolled
1236 OSThreadWaitState osts(this->osthread(), false /* not Object.wait() */);
1237
1238 jlong time_before_loop = os::javaTimeNanos();
1239
1240 while (true) {
1241 bool timedout = PeriodicTask_lock->wait(Mutex::_no_safepoint_check_flag,
1242 remaining);
1243 jlong now = os::javaTimeNanos();
1244
1245 if (remaining == 0) {
1246 // if we didn't have any tasks we could have waited for a long time
1247 // consider the time_slept zero and reset time_before_loop
1248 time_slept = 0;
1249 time_before_loop = now;
1250 } else {
1251 // need to recalculate since we might have new tasks in _tasks
1252 time_slept = (int) ((now - time_before_loop) / 1000000);
1253 }
1254
1255 // Change to task list or spurious wakeup of some kind
1256 if (timedout || _should_terminate) {
1257 break;
1258 }
1259
1260 remaining = PeriodicTask::time_to_wait();
1261 if (remaining == 0) {
1262 // Last task was just disenrolled so loop around and wait until
1263 // another task gets enrolled
1264 continue;
1265 }
1266
1267 remaining -= time_slept;
1268 if (remaining <= 0) {
1269 break;
1270 }
1271 }
1272
1273 return time_slept;
1274 }
1275
1276 void WatcherThread::run() {
1277 assert(this == watcher_thread(), "just checking");
1278
1279 this->record_stack_base_and_size();
1280 this->set_native_thread_name(this->name());
1281 this->set_active_handles(JNIHandleBlock::allocate_block());
1282 while (true) {
1283 assert(watcher_thread() == Thread::current(), "thread consistency check");
1284 assert(watcher_thread() == this, "thread consistency check");
1285
1286 // Calculate how long it'll be until the next PeriodicTask work
1287 // should be done, and sleep that amount of time.
1288 int time_waited = sleep();
1289
1290 if (is_error_reported()) {
1291 // A fatal error has happened, the error handler(VMError::report_and_die)
1292 // should abort JVM after creating an error log file. However in some
1293 // rare cases, the error handler itself might deadlock. Here periodically
1294 // check for error reporting timeouts, and if it happens, just proceed to
1295 // abort the VM.
1296
1297 // This code is in WatcherThread because WatcherThread wakes up
1298 // periodically so the fatal error handler doesn't need to do anything;
1299 // also because the WatcherThread is less likely to crash than other
1300 // threads.
1301
1302 for (;;) {
1303 // Note: we use naked sleep in this loop because we want to avoid using
1304 // any kind of VM infrastructure which may be broken at this point.
1305 if (VMError::check_timeout()) {
1306 // We hit error reporting timeout. Error reporting was interrupted and
1307 // will be wrapping things up now (closing files etc). Give it some more
1308 // time, then quit the VM.
1309 os::naked_short_sleep(200);
1310 // Print a message to stderr.
1311 fdStream err(defaultStream::output_fd());
1312 err.print_raw_cr("# [ timer expired, abort... ]");
1313 // skip atexit/vm_exit/vm_abort hooks
1314 os::die();
1315 }
1316
1317 // Wait a second, then recheck for timeout.
1318 os::naked_short_sleep(999);
1319 }
1320 }
1321
1322 if (_should_terminate) {
1323 // check for termination before posting the next tick
1324 break;
1325 }
1326
1327 PeriodicTask::real_time_tick(time_waited);
1328 }
1329
1330 // Signal that it is terminated
1331 {
1332 MutexLockerEx mu(Terminator_lock, Mutex::_no_safepoint_check_flag);
1333 _watcher_thread = NULL;
1334 Terminator_lock->notify();
1335 }
1336 }
1337
1338 void WatcherThread::start() {
1339 assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1340
1341 if (watcher_thread() == NULL && _startable) {
1342 _should_terminate = false;
1343 // Create the single instance of WatcherThread
1344 new WatcherThread();
1345 }
1346 }
1347
1348 void WatcherThread::make_startable() {
1349 assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1350 _startable = true;
1351 }
1352
1353 void WatcherThread::stop() {
1354 {
1355 // Follow normal safepoint aware lock enter protocol since the
1356 // WatcherThread is stopped by another JavaThread.
1357 MutexLocker ml(PeriodicTask_lock);
1358 _should_terminate = true;
1359
1360 WatcherThread* watcher = watcher_thread();
1361 if (watcher != NULL) {
1362 // unpark the WatcherThread so it can see that it should terminate
1363 watcher->unpark();
1364 }
1365 }
1366
1367 MutexLocker mu(Terminator_lock);
1368
1369 while (watcher_thread() != NULL) {
1370 // This wait should make safepoint checks, wait without a timeout,
1371 // and wait as a suspend-equivalent condition.
1372 //
1373 // Note: If the FlatProfiler is running, then this thread is waiting
1374 // for the WatcherThread to terminate and the WatcherThread, via the
1375 // FlatProfiler task, is waiting for the external suspend request on
1376 // this thread to complete. wait_for_ext_suspend_completion() will
1377 // eventually timeout, but that takes time. Making this wait a
1378 // suspend-equivalent condition solves that timeout problem.
1379 //
1380 Terminator_lock->wait(!Mutex::_no_safepoint_check_flag, 0,
1381 Mutex::_as_suspend_equivalent_flag);
1382 }
1383 }
1384
1385 void WatcherThread::unpark() {
1386 assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1387 PeriodicTask_lock->notify();
1388 }
1389
1390 void WatcherThread::print_on(outputStream* st) const {
1391 st->print("\"%s\" ", name());
1392 Thread::print_on(st);
1393 st->cr();
1394 }
1395
1396 // ======= JavaThread ========
1397
1398 #if INCLUDE_JVMCI
1399
1400 jlong* JavaThread::_jvmci_old_thread_counters;
1401
1402 bool jvmci_counters_include(JavaThread* thread) {
1403 oop threadObj = thread->threadObj();
1404 return !JVMCICountersExcludeCompiler || !thread->is_Compiler_thread();
1405 }
1406
1407 void JavaThread::collect_counters(typeArrayOop array) {
1408 if (JVMCICounterSize > 0) {
1409 MutexLocker tl(Threads_lock);
1410 for (int i = 0; i < array->length(); i++) {
1411 array->long_at_put(i, _jvmci_old_thread_counters[i]);
1412 }
1413 for (JavaThread* tp = Threads::first(); tp != NULL; tp = tp->next()) {
1414 if (jvmci_counters_include(tp)) {
1415 for (int i = 0; i < array->length(); i++) {
1416 array->long_at_put(i, array->long_at(i) + tp->_jvmci_counters[i]);
1417 }
1418 }
1419 }
1420 }
1421 }
1422
1423 #endif // INCLUDE_JVMCI
1424
1425 // A JavaThread is a normal Java thread
1426
1427 void JavaThread::initialize() {
1428 // Initialize fields
1429
1430 set_saved_exception_pc(NULL);
1431 set_threadObj(NULL);
1432 _anchor.clear();
1433 set_entry_point(NULL);
1434 set_jni_functions(jni_functions());
1435 set_callee_target(NULL);
1436 set_vm_result(NULL);
1437 set_vm_result_2(NULL);
1438 set_vframe_array_head(NULL);
1439 set_vframe_array_last(NULL);
1440 set_deferred_locals(NULL);
1441 set_deopt_mark(NULL);
1442 set_deopt_compiled_method(NULL);
1443 clear_must_deopt_id();
1444 set_monitor_chunks(NULL);
1445 set_next(NULL);
1446 set_thread_state(_thread_new);
1447 _terminated = _not_terminated;
1448 _privileged_stack_top = NULL;
1449 _array_for_gc = NULL;
1450 _suspend_equivalent = false;
1451 _in_deopt_handler = 0;
1452 _doing_unsafe_access = false;
1453 _stack_guard_state = stack_guard_unused;
1454 #if INCLUDE_JVMCI
1455 _pending_monitorenter = false;
1456 _pending_deoptimization = -1;
1457 _pending_failed_speculation = NULL;
1458 _pending_transfer_to_interpreter = false;
1459 _adjusting_comp_level = false;
1460 _jvmci._alternate_call_target = NULL;
1461 assert(_jvmci._implicit_exception_pc == NULL, "must be");
1462 if (JVMCICounterSize > 0) {
1463 _jvmci_counters = NEW_C_HEAP_ARRAY(jlong, JVMCICounterSize, mtInternal);
1464 memset(_jvmci_counters, 0, sizeof(jlong) * JVMCICounterSize);
1465 } else {
1466 _jvmci_counters = NULL;
1467 }
1468 #endif // INCLUDE_JVMCI
1469 _reserved_stack_activation = NULL; // stack base not known yet
1470 (void)const_cast<oop&>(_exception_oop = oop(NULL));
1471 _exception_pc = 0;
1472 _exception_handler_pc = 0;
1473 _is_method_handle_return = 0;
1474 _jvmti_thread_state= NULL;
1475 _should_post_on_exceptions_flag = JNI_FALSE;
1476 _jvmti_get_loaded_classes_closure = NULL;
1477 _interp_only_mode = 0;
1478 _special_runtime_exit_condition = _no_async_condition;
1479 _pending_async_exception = NULL;
1480 _thread_stat = NULL;
1481 _thread_stat = new ThreadStatistics();
1482 _blocked_on_compilation = false;
1483 _jni_active_critical = 0;
1484 _pending_jni_exception_check_fn = NULL;
1485 _do_not_unlock_if_synchronized = false;
1486 _cached_monitor_info = NULL;
1487 _parker = Parker::Allocate(this);
1488
1489 #ifndef PRODUCT
1490 _jmp_ring_index = 0;
1491 for (int ji = 0; ji < jump_ring_buffer_size; ji++) {
1492 record_jump(NULL, NULL, NULL, 0);
1493 }
1494 #endif // PRODUCT
1495
1496 set_thread_profiler(NULL);
1497 if (FlatProfiler::is_active()) {
1498 // This is where we would decide to either give each thread it's own profiler
1499 // or use one global one from FlatProfiler,
1500 // or up to some count of the number of profiled threads, etc.
1501 ThreadProfiler* pp = new ThreadProfiler();
1502 pp->engage();
1503 set_thread_profiler(pp);
1504 }
1505
1506 // Setup safepoint state info for this thread
1507 ThreadSafepointState::create(this);
1508
1509 debug_only(_java_call_counter = 0);
1510
1511 // JVMTI PopFrame support
1512 _popframe_condition = popframe_inactive;
1513 _popframe_preserved_args = NULL;
1514 _popframe_preserved_args_size = 0;
1515 _frames_to_pop_failed_realloc = 0;
1516
1517 pd_initialize();
1518 }
1519
1520 #if INCLUDE_ALL_GCS
1521 SATBMarkQueueSet JavaThread::_satb_mark_queue_set;
1522 DirtyCardQueueSet JavaThread::_dirty_card_queue_set;
1523 #endif // INCLUDE_ALL_GCS
1524
1525 JavaThread::JavaThread(bool is_attaching_via_jni) :
1526 Thread()
1527 #if INCLUDE_ALL_GCS
1528 , _satb_mark_queue(&_satb_mark_queue_set),
1529 _dirty_card_queue(&_dirty_card_queue_set)
1530 #endif // INCLUDE_ALL_GCS
1531 {
1532 initialize();
1533 if (is_attaching_via_jni) {
1534 _jni_attach_state = _attaching_via_jni;
1535 } else {
1536 _jni_attach_state = _not_attaching_via_jni;
1537 }
1538 assert(deferred_card_mark().is_empty(), "Default MemRegion ctor");
1539 }
1540
1541 bool JavaThread::reguard_stack(address cur_sp) {
1542 if (_stack_guard_state != stack_guard_yellow_reserved_disabled
1543 && _stack_guard_state != stack_guard_reserved_disabled) {
1544 return true; // Stack already guarded or guard pages not needed.
1545 }
1546
1547 if (register_stack_overflow()) {
1548 // For those architectures which have separate register and
1549 // memory stacks, we must check the register stack to see if
1550 // it has overflowed.
1551 return false;
1552 }
1553
1554 // Java code never executes within the yellow zone: the latter is only
1555 // there to provoke an exception during stack banging. If java code
1556 // is executing there, either StackShadowPages should be larger, or
1557 // some exception code in c1, c2 or the interpreter isn't unwinding
1558 // when it should.
1559 guarantee(cur_sp > stack_reserved_zone_base(),
1560 "not enough space to reguard - increase StackShadowPages");
1561 if (_stack_guard_state == stack_guard_yellow_reserved_disabled) {
1562 enable_stack_yellow_reserved_zone();
1563 if (reserved_stack_activation() != stack_base()) {
1564 set_reserved_stack_activation(stack_base());
1565 }
1566 } else if (_stack_guard_state == stack_guard_reserved_disabled) {
1567 set_reserved_stack_activation(stack_base());
1568 enable_stack_reserved_zone();
1569 }
1570 return true;
1571 }
1572
1573 bool JavaThread::reguard_stack(void) {
1574 return reguard_stack(os::current_stack_pointer());
1575 }
1576
1577
1578 void JavaThread::block_if_vm_exited() {
1579 if (_terminated == _vm_exited) {
1580 // _vm_exited is set at safepoint, and Threads_lock is never released
1581 // we will block here forever
1582 Threads_lock->lock_without_safepoint_check();
1583 ShouldNotReachHere();
1584 }
1585 }
1586
1587
1588 // Remove this ifdef when C1 is ported to the compiler interface.
1589 static void compiler_thread_entry(JavaThread* thread, TRAPS);
1590 static void sweeper_thread_entry(JavaThread* thread, TRAPS);
1591
1592 JavaThread::JavaThread(ThreadFunction entry_point, size_t stack_sz) :
1593 Thread()
1594 #if INCLUDE_ALL_GCS
1595 , _satb_mark_queue(&_satb_mark_queue_set),
1596 _dirty_card_queue(&_dirty_card_queue_set)
1597 #endif // INCLUDE_ALL_GCS
1598 {
1599 initialize();
1600 _jni_attach_state = _not_attaching_via_jni;
1601 set_entry_point(entry_point);
1602 // Create the native thread itself.
1603 // %note runtime_23
1604 os::ThreadType thr_type = os::java_thread;
1605 thr_type = entry_point == &compiler_thread_entry ? os::compiler_thread :
1606 os::java_thread;
1607 os::create_thread(this, thr_type, stack_sz);
1608 // The _osthread may be NULL here because we ran out of memory (too many threads active).
1609 // We need to throw and OutOfMemoryError - however we cannot do this here because the caller
1610 // may hold a lock and all locks must be unlocked before throwing the exception (throwing
1611 // the exception consists of creating the exception object & initializing it, initialization
1612 // will leave the VM via a JavaCall and then all locks must be unlocked).
1613 //
1614 // The thread is still suspended when we reach here. Thread must be explicit started
1615 // by creator! Furthermore, the thread must also explicitly be added to the Threads list
1616 // by calling Threads:add. The reason why this is not done here, is because the thread
1617 // object must be fully initialized (take a look at JVM_Start)
1618 }
1619
1620 JavaThread::~JavaThread() {
1621
1622 // JSR166 -- return the parker to the free list
1623 Parker::Release(_parker);
1624 _parker = NULL;
1625
1626 // Free any remaining previous UnrollBlock
1627 vframeArray* old_array = vframe_array_last();
1628
1629 if (old_array != NULL) {
1630 Deoptimization::UnrollBlock* old_info = old_array->unroll_block();
1631 old_array->set_unroll_block(NULL);
1632 delete old_info;
1633 delete old_array;
1634 }
1635
1636 GrowableArray<jvmtiDeferredLocalVariableSet*>* deferred = deferred_locals();
1637 if (deferred != NULL) {
1638 // This can only happen if thread is destroyed before deoptimization occurs.
1639 assert(deferred->length() != 0, "empty array!");
1640 do {
1641 jvmtiDeferredLocalVariableSet* dlv = deferred->at(0);
1642 deferred->remove_at(0);
1643 // individual jvmtiDeferredLocalVariableSet are CHeapObj's
1644 delete dlv;
1645 } while (deferred->length() != 0);
1646 delete deferred;
1647 }
1648
1649 // All Java related clean up happens in exit
1650 ThreadSafepointState::destroy(this);
1651 if (_thread_profiler != NULL) delete _thread_profiler;
1652 if (_thread_stat != NULL) delete _thread_stat;
1653
1654 #if INCLUDE_JVMCI
1655 if (JVMCICounterSize > 0) {
1656 if (jvmci_counters_include(this)) {
1657 for (int i = 0; i < JVMCICounterSize; i++) {
1658 _jvmci_old_thread_counters[i] += _jvmci_counters[i];
1659 }
1660 }
1661 FREE_C_HEAP_ARRAY(jlong, _jvmci_counters);
1662 }
1663 #endif // INCLUDE_JVMCI
1664 }
1665
1666
1667 // The first routine called by a new Java thread
1668 void JavaThread::run() {
1669 // initialize thread-local alloc buffer related fields
1670 this->initialize_tlab();
1671
1672 // used to test validity of stack trace backs
1673 this->record_base_of_stack_pointer();
1674
1675 // Record real stack base and size.
1676 this->record_stack_base_and_size();
1677
1678 this->create_stack_guard_pages();
1679
1680 this->cache_global_variables();
1681
1682 // Thread is now sufficient initialized to be handled by the safepoint code as being
1683 // in the VM. Change thread state from _thread_new to _thread_in_vm
1684 ThreadStateTransition::transition_and_fence(this, _thread_new, _thread_in_vm);
1685
1686 assert(JavaThread::current() == this, "sanity check");
1687 assert(!Thread::current()->owns_locks(), "sanity check");
1688
1689 DTRACE_THREAD_PROBE(start, this);
1690
1691 // This operation might block. We call that after all safepoint checks for a new thread has
1692 // been completed.
1693 this->set_active_handles(JNIHandleBlock::allocate_block());
1694
1695 if (JvmtiExport::should_post_thread_life()) {
1696 JvmtiExport::post_thread_start(this);
1697 }
1698
1699 EventThreadStart event;
1700 if (event.should_commit()) {
1701 event.set_thread(THREAD_TRACE_ID(this));
1702 event.commit();
1703 }
1704
1705 // We call another function to do the rest so we are sure that the stack addresses used
1706 // from there will be lower than the stack base just computed
1707 thread_main_inner();
1708
1709 // Note, thread is no longer valid at this point!
1710 }
1711
1712
1713 void JavaThread::thread_main_inner() {
1714 assert(JavaThread::current() == this, "sanity check");
1715 assert(this->threadObj() != NULL, "just checking");
1716
1717 // Execute thread entry point unless this thread has a pending exception
1718 // or has been stopped before starting.
1719 // Note: Due to JVM_StopThread we can have pending exceptions already!
1720 if (!this->has_pending_exception() &&
1721 !java_lang_Thread::is_stillborn(this->threadObj())) {
1722 {
1723 ResourceMark rm(this);
1724 this->set_native_thread_name(this->get_thread_name());
1725 }
1726 HandleMark hm(this);
1727 this->entry_point()(this, this);
1728 }
1729
1730 DTRACE_THREAD_PROBE(stop, this);
1731
1732 this->exit(false);
1733 delete this;
1734 }
1735
1736
1737 static void ensure_join(JavaThread* thread) {
1738 // We do not need to grap the Threads_lock, since we are operating on ourself.
1739 Handle threadObj(thread, thread->threadObj());
1740 assert(threadObj.not_null(), "java thread object must exist");
1741 ObjectLocker lock(threadObj, thread);
1742 // Ignore pending exception (ThreadDeath), since we are exiting anyway
1743 thread->clear_pending_exception();
1744 // Thread is exiting. So set thread_status field in java.lang.Thread class to TERMINATED.
1745 java_lang_Thread::set_thread_status(threadObj(), java_lang_Thread::TERMINATED);
1746 // Clear the native thread instance - this makes isAlive return false and allows the join()
1747 // to complete once we've done the notify_all below
1748 java_lang_Thread::set_thread(threadObj(), NULL);
1749 lock.notify_all(thread);
1750 // Ignore pending exception (ThreadDeath), since we are exiting anyway
1751 thread->clear_pending_exception();
1752 }
1753
1754
1755 // For any new cleanup additions, please check to see if they need to be applied to
1756 // cleanup_failed_attach_current_thread as well.
1757 void JavaThread::exit(bool destroy_vm, ExitType exit_type) {
1758 assert(this == JavaThread::current(), "thread consistency check");
1759
1760 HandleMark hm(this);
1761 Handle uncaught_exception(this, this->pending_exception());
1762 this->clear_pending_exception();
1763 Handle threadObj(this, this->threadObj());
1764 assert(threadObj.not_null(), "Java thread object should be created");
1765
1766 if (get_thread_profiler() != NULL) {
1767 get_thread_profiler()->disengage();
1768 ResourceMark rm;
1769 get_thread_profiler()->print(get_thread_name());
1770 }
1771
1772
1773 // FIXIT: This code should be moved into else part, when reliable 1.2/1.3 check is in place
1774 {
1775 EXCEPTION_MARK;
1776
1777 CLEAR_PENDING_EXCEPTION;
1778 }
1779 if (!destroy_vm) {
1780 if (uncaught_exception.not_null()) {
1781 EXCEPTION_MARK;
1782 // Call method Thread.dispatchUncaughtException().
1783 Klass* thread_klass = SystemDictionary::Thread_klass();
1784 JavaValue result(T_VOID);
1785 JavaCalls::call_virtual(&result,
1786 threadObj, thread_klass,
1787 vmSymbols::dispatchUncaughtException_name(),
1788 vmSymbols::throwable_void_signature(),
1789 uncaught_exception,
1790 THREAD);
1791 if (HAS_PENDING_EXCEPTION) {
1792 ResourceMark rm(this);
1793 jio_fprintf(defaultStream::error_stream(),
1794 "\nException: %s thrown from the UncaughtExceptionHandler"
1795 " in thread \"%s\"\n",
1796 pending_exception()->klass()->external_name(),
1797 get_thread_name());
1798 CLEAR_PENDING_EXCEPTION;
1799 }
1800 }
1801
1802 // Called before the java thread exit since we want to read info
1803 // from java_lang_Thread object
1804 EventThreadEnd event;
1805 if (event.should_commit()) {
1806 event.set_thread(THREAD_TRACE_ID(this));
1807 event.commit();
1808 }
1809
1810 // Call after last event on thread
1811 EVENT_THREAD_EXIT(this);
1812
1813 // Call Thread.exit(). We try 3 times in case we got another Thread.stop during
1814 // the execution of the method. If that is not enough, then we don't really care. Thread.stop
1815 // is deprecated anyhow.
1816 if (!is_Compiler_thread()) {
1817 int count = 3;
1818 while (java_lang_Thread::threadGroup(threadObj()) != NULL && (count-- > 0)) {
1819 EXCEPTION_MARK;
1820 JavaValue result(T_VOID);
1821 Klass* thread_klass = SystemDictionary::Thread_klass();
1822 JavaCalls::call_virtual(&result,
1823 threadObj, thread_klass,
1824 vmSymbols::exit_method_name(),
1825 vmSymbols::void_method_signature(),
1826 THREAD);
1827 CLEAR_PENDING_EXCEPTION;
1828 }
1829 }
1830 // notify JVMTI
1831 if (JvmtiExport::should_post_thread_life()) {
1832 JvmtiExport::post_thread_end(this);
1833 }
1834
1835 // We have notified the agents that we are exiting, before we go on,
1836 // we must check for a pending external suspend request and honor it
1837 // in order to not surprise the thread that made the suspend request.
1838 while (true) {
1839 {
1840 MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
1841 if (!is_external_suspend()) {
1842 set_terminated(_thread_exiting);
1843 ThreadService::current_thread_exiting(this);
1844 break;
1845 }
1846 // Implied else:
1847 // Things get a little tricky here. We have a pending external
1848 // suspend request, but we are holding the SR_lock so we
1849 // can't just self-suspend. So we temporarily drop the lock
1850 // and then self-suspend.
1851 }
1852
1853 ThreadBlockInVM tbivm(this);
1854 java_suspend_self();
1855
1856 // We're done with this suspend request, but we have to loop around
1857 // and check again. Eventually we will get SR_lock without a pending
1858 // external suspend request and will be able to mark ourselves as
1859 // exiting.
1860 }
1861 // no more external suspends are allowed at this point
1862 } else {
1863 // before_exit() has already posted JVMTI THREAD_END events
1864 }
1865
1866 // Notify waiters on thread object. This has to be done after exit() is called
1867 // on the thread (if the thread is the last thread in a daemon ThreadGroup the
1868 // group should have the destroyed bit set before waiters are notified).
1869 ensure_join(this);
1870 assert(!this->has_pending_exception(), "ensure_join should have cleared");
1871
1872 // 6282335 JNI DetachCurrentThread spec states that all Java monitors
1873 // held by this thread must be released. The spec does not distinguish
1874 // between JNI-acquired and regular Java monitors. We can only see
1875 // regular Java monitors here if monitor enter-exit matching is broken.
1876 //
1877 // Optionally release any monitors for regular JavaThread exits. This
1878 // is provided as a work around for any bugs in monitor enter-exit
1879 // matching. This can be expensive so it is not enabled by default.
1880 //
1881 // ensure_join() ignores IllegalThreadStateExceptions, and so does
1882 // ObjectSynchronizer::release_monitors_owned_by_thread().
1883 if (exit_type == jni_detach || ObjectMonitor::Knob_ExitRelease) {
1884 // Sanity check even though JNI DetachCurrentThread() would have
1885 // returned JNI_ERR if there was a Java frame. JavaThread exit
1886 // should be done executing Java code by the time we get here.
1887 assert(!this->has_last_Java_frame(),
1888 "should not have a Java frame when detaching or exiting");
1889 ObjectSynchronizer::release_monitors_owned_by_thread(this);
1890 assert(!this->has_pending_exception(), "release_monitors should have cleared");
1891 }
1892
1893 // These things needs to be done while we are still a Java Thread. Make sure that thread
1894 // is in a consistent state, in case GC happens
1895 assert(_privileged_stack_top == NULL, "must be NULL when we get here");
1896
1897 if (active_handles() != NULL) {
1898 JNIHandleBlock* block = active_handles();
1899 set_active_handles(NULL);
1900 JNIHandleBlock::release_block(block);
1901 }
1902
1903 if (free_handle_block() != NULL) {
1904 JNIHandleBlock* block = free_handle_block();
1905 set_free_handle_block(NULL);
1906 JNIHandleBlock::release_block(block);
1907 }
1908
1909 // These have to be removed while this is still a valid thread.
1910 remove_stack_guard_pages();
1911
1912 if (UseTLAB) {
1913 tlab().make_parsable(true); // retire TLAB
1914 }
1915
1916 if (JvmtiEnv::environments_might_exist()) {
1917 JvmtiExport::cleanup_thread(this);
1918 }
1919
1920 // We must flush any deferred card marks before removing a thread from
1921 // the list of active threads.
1922 Universe::heap()->flush_deferred_store_barrier(this);
1923 assert(deferred_card_mark().is_empty(), "Should have been flushed");
1924
1925 #if INCLUDE_ALL_GCS
1926 // We must flush the G1-related buffers before removing a thread
1927 // from the list of active threads. We must do this after any deferred
1928 // card marks have been flushed (above) so that any entries that are
1929 // added to the thread's dirty card queue as a result are not lost.
1930 if (UseG1GC) {
1931 flush_barrier_queues();
1932 }
1933 #endif // INCLUDE_ALL_GCS
1934
1935 log_info(os, thread)("JavaThread %s (tid: " UINTX_FORMAT ").",
1936 exit_type == JavaThread::normal_exit ? "exiting" : "detaching",
1937 os::current_thread_id());
1938
1939 // Remove from list of active threads list, and notify VM thread if we are the last non-daemon thread
1940 Threads::remove(this);
1941 }
1942
1943 #if INCLUDE_ALL_GCS
1944 // Flush G1-related queues.
1945 void JavaThread::flush_barrier_queues() {
1946 satb_mark_queue().flush();
1947 dirty_card_queue().flush();
1948 }
1949
1950 void JavaThread::initialize_queues() {
1951 assert(!SafepointSynchronize::is_at_safepoint(),
1952 "we should not be at a safepoint");
1953
1954 SATBMarkQueue& satb_queue = satb_mark_queue();
1955 SATBMarkQueueSet& satb_queue_set = satb_mark_queue_set();
1956 // The SATB queue should have been constructed with its active
1957 // field set to false.
1958 assert(!satb_queue.is_active(), "SATB queue should not be active");
1959 assert(satb_queue.is_empty(), "SATB queue should be empty");
1960 // If we are creating the thread during a marking cycle, we should
1961 // set the active field of the SATB queue to true.
1962 if (satb_queue_set.is_active()) {
1963 satb_queue.set_active(true);
1964 }
1965
1966 DirtyCardQueue& dirty_queue = dirty_card_queue();
1967 // The dirty card queue should have been constructed with its
1968 // active field set to true.
1969 assert(dirty_queue.is_active(), "dirty card queue should be active");
1970 }
1971 #endif // INCLUDE_ALL_GCS
1972
1973 void JavaThread::cleanup_failed_attach_current_thread() {
1974 if (get_thread_profiler() != NULL) {
1975 get_thread_profiler()->disengage();
1976 ResourceMark rm;
1977 get_thread_profiler()->print(get_thread_name());
1978 }
1979
1980 if (active_handles() != NULL) {
1981 JNIHandleBlock* block = active_handles();
1982 set_active_handles(NULL);
1983 JNIHandleBlock::release_block(block);
1984 }
1985
1986 if (free_handle_block() != NULL) {
1987 JNIHandleBlock* block = free_handle_block();
1988 set_free_handle_block(NULL);
1989 JNIHandleBlock::release_block(block);
1990 }
1991
1992 // These have to be removed while this is still a valid thread.
1993 remove_stack_guard_pages();
1994
1995 if (UseTLAB) {
1996 tlab().make_parsable(true); // retire TLAB, if any
1997 }
1998
1999 #if INCLUDE_ALL_GCS
2000 if (UseG1GC) {
2001 flush_barrier_queues();
2002 }
2003 #endif // INCLUDE_ALL_GCS
2004
2005 Threads::remove(this);
2006 delete this;
2007 }
2008
2009
2010
2011
2012 JavaThread* JavaThread::active() {
2013 Thread* thread = Thread::current();
2014 if (thread->is_Java_thread()) {
2015 return (JavaThread*) thread;
2016 } else {
2017 assert(thread->is_VM_thread(), "this must be a vm thread");
2018 VM_Operation* op = ((VMThread*) thread)->vm_operation();
2019 JavaThread *ret=op == NULL ? NULL : (JavaThread *)op->calling_thread();
2020 assert(ret->is_Java_thread(), "must be a Java thread");
2021 return ret;
2022 }
2023 }
2024
2025 bool JavaThread::is_lock_owned(address adr) const {
2026 if (Thread::is_lock_owned(adr)) return true;
2027
2028 for (MonitorChunk* chunk = monitor_chunks(); chunk != NULL; chunk = chunk->next()) {
2029 if (chunk->contains(adr)) return true;
2030 }
2031
2032 return false;
2033 }
2034
2035
2036 void JavaThread::add_monitor_chunk(MonitorChunk* chunk) {
2037 chunk->set_next(monitor_chunks());
2038 set_monitor_chunks(chunk);
2039 }
2040
2041 void JavaThread::remove_monitor_chunk(MonitorChunk* chunk) {
2042 guarantee(monitor_chunks() != NULL, "must be non empty");
2043 if (monitor_chunks() == chunk) {
2044 set_monitor_chunks(chunk->next());
2045 } else {
2046 MonitorChunk* prev = monitor_chunks();
2047 while (prev->next() != chunk) prev = prev->next();
2048 prev->set_next(chunk->next());
2049 }
2050 }
2051
2052 // JVM support.
2053
2054 // Note: this function shouldn't block if it's called in
2055 // _thread_in_native_trans state (such as from
2056 // check_special_condition_for_native_trans()).
2057 void JavaThread::check_and_handle_async_exceptions(bool check_unsafe_error) {
2058
2059 if (has_last_Java_frame() && has_async_condition()) {
2060 // If we are at a polling page safepoint (not a poll return)
2061 // then we must defer async exception because live registers
2062 // will be clobbered by the exception path. Poll return is
2063 // ok because the call we a returning from already collides
2064 // with exception handling registers and so there is no issue.
2065 // (The exception handling path kills call result registers but
2066 // this is ok since the exception kills the result anyway).
2067
2068 if (is_at_poll_safepoint()) {
2069 // if the code we are returning to has deoptimized we must defer
2070 // the exception otherwise live registers get clobbered on the
2071 // exception path before deoptimization is able to retrieve them.
2072 //
2073 RegisterMap map(this, false);
2074 frame caller_fr = last_frame().sender(&map);
2075 assert(caller_fr.is_compiled_frame(), "what?");
2076 if (caller_fr.is_deoptimized_frame()) {
2077 log_info(exceptions)("deferred async exception at compiled safepoint");
2078 return;
2079 }
2080 }
2081 }
2082
2083 JavaThread::AsyncRequests condition = clear_special_runtime_exit_condition();
2084 if (condition == _no_async_condition) {
2085 // Conditions have changed since has_special_runtime_exit_condition()
2086 // was called:
2087 // - if we were here only because of an external suspend request,
2088 // then that was taken care of above (or cancelled) so we are done
2089 // - if we were here because of another async request, then it has
2090 // been cleared between the has_special_runtime_exit_condition()
2091 // and now so again we are done
2092 return;
2093 }
2094
2095 // Check for pending async. exception
2096 if (_pending_async_exception != NULL) {
2097 // Only overwrite an already pending exception, if it is not a threadDeath.
2098 if (!has_pending_exception() || !pending_exception()->is_a(SystemDictionary::ThreadDeath_klass())) {
2099
2100 // We cannot call Exceptions::_throw(...) here because we cannot block
2101 set_pending_exception(_pending_async_exception, __FILE__, __LINE__);
2102
2103 if (log_is_enabled(Info, exceptions)) {
2104 ResourceMark rm;
2105 outputStream* logstream = Log(exceptions)::info_stream();
2106 logstream->print("Async. exception installed at runtime exit (" INTPTR_FORMAT ")", p2i(this));
2107 if (has_last_Java_frame()) {
2108 frame f = last_frame();
2109 logstream->print(" (pc: " INTPTR_FORMAT " sp: " INTPTR_FORMAT " )", p2i(f.pc()), p2i(f.sp()));
2110 }
2111 logstream->print_cr(" of type: %s", _pending_async_exception->klass()->external_name());
2112 }
2113 _pending_async_exception = NULL;
2114 clear_has_async_exception();
2115 }
2116 }
2117
2118 if (check_unsafe_error &&
2119 condition == _async_unsafe_access_error && !has_pending_exception()) {
2120 condition = _no_async_condition; // done
2121 switch (thread_state()) {
2122 case _thread_in_vm: {
2123 JavaThread* THREAD = this;
2124 THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in an unsafe memory access operation");
2125 }
2126 case _thread_in_native: {
2127 ThreadInVMfromNative tiv(this);
2128 JavaThread* THREAD = this;
2129 THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in an unsafe memory access operation");
2130 }
2131 case _thread_in_Java: {
2132 ThreadInVMfromJava tiv(this);
2133 JavaThread* THREAD = this;
2134 THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in a recent unsafe memory access operation in compiled Java code");
2135 }
2136 default:
2137 ShouldNotReachHere();
2138 }
2139 }
2140
2141 assert(condition == _no_async_condition || has_pending_exception() ||
2142 (!check_unsafe_error && condition == _async_unsafe_access_error),
2143 "must have handled the async condition, if no exception");
2144 }
2145
2146 void JavaThread::handle_special_runtime_exit_condition(bool check_asyncs) {
2147 //
2148 // Check for pending external suspend. Internal suspend requests do
2149 // not use handle_special_runtime_exit_condition().
2150 // If JNIEnv proxies are allowed, don't self-suspend if the target
2151 // thread is not the current thread. In older versions of jdbx, jdbx
2152 // threads could call into the VM with another thread's JNIEnv so we
2153 // can be here operating on behalf of a suspended thread (4432884).
2154 bool do_self_suspend = is_external_suspend_with_lock();
2155 if (do_self_suspend && (!AllowJNIEnvProxy || this == JavaThread::current())) {
2156 //
2157 // Because thread is external suspended the safepoint code will count
2158 // thread as at a safepoint. This can be odd because we can be here
2159 // as _thread_in_Java which would normally transition to _thread_blocked
2160 // at a safepoint. We would like to mark the thread as _thread_blocked
2161 // before calling java_suspend_self like all other callers of it but
2162 // we must then observe proper safepoint protocol. (We can't leave
2163 // _thread_blocked with a safepoint in progress). However we can be
2164 // here as _thread_in_native_trans so we can't use a normal transition
2165 // constructor/destructor pair because they assert on that type of
2166 // transition. We could do something like:
2167 //
2168 // JavaThreadState state = thread_state();
2169 // set_thread_state(_thread_in_vm);
2170 // {
2171 // ThreadBlockInVM tbivm(this);
2172 // java_suspend_self()
2173 // }
2174 // set_thread_state(_thread_in_vm_trans);
2175 // if (safepoint) block;
2176 // set_thread_state(state);
2177 //
2178 // but that is pretty messy. Instead we just go with the way the
2179 // code has worked before and note that this is the only path to
2180 // java_suspend_self that doesn't put the thread in _thread_blocked
2181 // mode.
2182
2183 frame_anchor()->make_walkable(this);
2184 java_suspend_self();
2185
2186 // We might be here for reasons in addition to the self-suspend request
2187 // so check for other async requests.
2188 }
2189
2190 if (check_asyncs) {
2191 check_and_handle_async_exceptions();
2192 }
2193 }
2194
2195 void JavaThread::send_thread_stop(oop java_throwable) {
2196 assert(Thread::current()->is_VM_thread(), "should be in the vm thread");
2197 assert(Threads_lock->is_locked(), "Threads_lock should be locked by safepoint code");
2198 assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");
2199
2200 // Do not throw asynchronous exceptions against the compiler thread
2201 // (the compiler thread should not be a Java thread -- fix in 1.4.2)
2202 if (!can_call_java()) return;
2203
2204 {
2205 // Actually throw the Throwable against the target Thread - however
2206 // only if there is no thread death exception installed already.
2207 if (_pending_async_exception == NULL || !_pending_async_exception->is_a(SystemDictionary::ThreadDeath_klass())) {
2208 // If the topmost frame is a runtime stub, then we are calling into
2209 // OptoRuntime from compiled code. Some runtime stubs (new, monitor_exit..)
2210 // must deoptimize the caller before continuing, as the compiled exception handler table
2211 // may not be valid
2212 if (has_last_Java_frame()) {
2213 frame f = last_frame();
2214 if (f.is_runtime_frame() || f.is_safepoint_blob_frame()) {
2215 // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2216 RegisterMap reg_map(this, UseBiasedLocking);
2217 frame compiled_frame = f.sender(®_map);
2218 if (!StressCompiledExceptionHandlers && compiled_frame.can_be_deoptimized()) {
2219 Deoptimization::deoptimize(this, compiled_frame, ®_map);
2220 }
2221 }
2222 }
2223
2224 // Set async. pending exception in thread.
2225 set_pending_async_exception(java_throwable);
2226
2227 if (log_is_enabled(Info, exceptions)) {
2228 ResourceMark rm;
2229 log_info(exceptions)("Pending Async. exception installed of type: %s",
2230 InstanceKlass::cast(_pending_async_exception->klass())->external_name());
2231 }
2232 // for AbortVMOnException flag
2233 Exceptions::debug_check_abort(_pending_async_exception->klass()->external_name());
2234 }
2235 }
2236
2237
2238 // Interrupt thread so it will wake up from a potential wait()
2239 Thread::interrupt(this);
2240 }
2241
2242 // External suspension mechanism.
2243 //
2244 // Tell the VM to suspend a thread when ever it knows that it does not hold on
2245 // to any VM_locks and it is at a transition
2246 // Self-suspension will happen on the transition out of the vm.
2247 // Catch "this" coming in from JNIEnv pointers when the thread has been freed
2248 //
2249 // Guarantees on return:
2250 // + Target thread will not execute any new bytecode (that's why we need to
2251 // force a safepoint)
2252 // + Target thread will not enter any new monitors
2253 //
2254 void JavaThread::java_suspend() {
2255 { MutexLocker mu(Threads_lock);
2256 if (!Threads::includes(this) || is_exiting() || this->threadObj() == NULL) {
2257 return;
2258 }
2259 }
2260
2261 { MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2262 if (!is_external_suspend()) {
2263 // a racing resume has cancelled us; bail out now
2264 return;
2265 }
2266
2267 // suspend is done
2268 uint32_t debug_bits = 0;
2269 // Warning: is_ext_suspend_completed() may temporarily drop the
2270 // SR_lock to allow the thread to reach a stable thread state if
2271 // it is currently in a transient thread state.
2272 if (is_ext_suspend_completed(false /* !called_by_wait */,
2273 SuspendRetryDelay, &debug_bits)) {
2274 return;
2275 }
2276 }
2277
2278 VM_ForceSafepoint vm_suspend;
2279 VMThread::execute(&vm_suspend);
2280 }
2281
2282 // Part II of external suspension.
2283 // A JavaThread self suspends when it detects a pending external suspend
2284 // request. This is usually on transitions. It is also done in places
2285 // where continuing to the next transition would surprise the caller,
2286 // e.g., monitor entry.
2287 //
2288 // Returns the number of times that the thread self-suspended.
2289 //
2290 // Note: DO NOT call java_suspend_self() when you just want to block current
2291 // thread. java_suspend_self() is the second stage of cooperative
2292 // suspension for external suspend requests and should only be used
2293 // to complete an external suspend request.
2294 //
2295 int JavaThread::java_suspend_self() {
2296 int ret = 0;
2297
2298 // we are in the process of exiting so don't suspend
2299 if (is_exiting()) {
2300 clear_external_suspend();
2301 return ret;
2302 }
2303
2304 assert(_anchor.walkable() ||
2305 (is_Java_thread() && !((JavaThread*)this)->has_last_Java_frame()),
2306 "must have walkable stack");
2307
2308 MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2309
2310 assert(!this->is_ext_suspended(),
2311 "a thread trying to self-suspend should not already be suspended");
2312
2313 if (this->is_suspend_equivalent()) {
2314 // If we are self-suspending as a result of the lifting of a
2315 // suspend equivalent condition, then the suspend_equivalent
2316 // flag is not cleared until we set the ext_suspended flag so
2317 // that wait_for_ext_suspend_completion() returns consistent
2318 // results.
2319 this->clear_suspend_equivalent();
2320 }
2321
2322 // A racing resume may have cancelled us before we grabbed SR_lock
2323 // above. Or another external suspend request could be waiting for us
2324 // by the time we return from SR_lock()->wait(). The thread
2325 // that requested the suspension may already be trying to walk our
2326 // stack and if we return now, we can change the stack out from under
2327 // it. This would be a "bad thing (TM)" and cause the stack walker
2328 // to crash. We stay self-suspended until there are no more pending
2329 // external suspend requests.
2330 while (is_external_suspend()) {
2331 ret++;
2332 this->set_ext_suspended();
2333
2334 // _ext_suspended flag is cleared by java_resume()
2335 while (is_ext_suspended()) {
2336 this->SR_lock()->wait(Mutex::_no_safepoint_check_flag);
2337 }
2338 }
2339
2340 return ret;
2341 }
2342
2343 #ifdef ASSERT
2344 // verify the JavaThread has not yet been published in the Threads::list, and
2345 // hence doesn't need protection from concurrent access at this stage
2346 void JavaThread::verify_not_published() {
2347 if (!Threads_lock->owned_by_self()) {
2348 MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
2349 assert(!Threads::includes(this),
2350 "java thread shouldn't have been published yet!");
2351 } else {
2352 assert(!Threads::includes(this),
2353 "java thread shouldn't have been published yet!");
2354 }
2355 }
2356 #endif
2357
2358 // Slow path when the native==>VM/Java barriers detect a safepoint is in
2359 // progress or when _suspend_flags is non-zero.
2360 // Current thread needs to self-suspend if there is a suspend request and/or
2361 // block if a safepoint is in progress.
2362 // Async exception ISN'T checked.
2363 // Note only the ThreadInVMfromNative transition can call this function
2364 // directly and when thread state is _thread_in_native_trans
2365 void JavaThread::check_safepoint_and_suspend_for_native_trans(JavaThread *thread) {
2366 assert(thread->thread_state() == _thread_in_native_trans, "wrong state");
2367
2368 JavaThread *curJT = JavaThread::current();
2369 bool do_self_suspend = thread->is_external_suspend();
2370
2371 assert(!curJT->has_last_Java_frame() || curJT->frame_anchor()->walkable(), "Unwalkable stack in native->vm transition");
2372
2373 // If JNIEnv proxies are allowed, don't self-suspend if the target
2374 // thread is not the current thread. In older versions of jdbx, jdbx
2375 // threads could call into the VM with another thread's JNIEnv so we
2376 // can be here operating on behalf of a suspended thread (4432884).
2377 if (do_self_suspend && (!AllowJNIEnvProxy || curJT == thread)) {
2378 JavaThreadState state = thread->thread_state();
2379
2380 // We mark this thread_blocked state as a suspend-equivalent so
2381 // that a caller to is_ext_suspend_completed() won't be confused.
2382 // The suspend-equivalent state is cleared by java_suspend_self().
2383 thread->set_suspend_equivalent();
2384
2385 // If the safepoint code sees the _thread_in_native_trans state, it will
2386 // wait until the thread changes to other thread state. There is no
2387 // guarantee on how soon we can obtain the SR_lock and complete the
2388 // self-suspend request. It would be a bad idea to let safepoint wait for
2389 // too long. Temporarily change the state to _thread_blocked to
2390 // let the VM thread know that this thread is ready for GC. The problem
2391 // of changing thread state is that safepoint could happen just after
2392 // java_suspend_self() returns after being resumed, and VM thread will
2393 // see the _thread_blocked state. We must check for safepoint
2394 // after restoring the state and make sure we won't leave while a safepoint
2395 // is in progress.
2396 thread->set_thread_state(_thread_blocked);
2397 thread->java_suspend_self();
2398 thread->set_thread_state(state);
2399 // Make sure new state is seen by VM thread
2400 if (os::is_MP()) {
2401 if (UseMembar) {
2402 // Force a fence between the write above and read below
2403 OrderAccess::fence();
2404 } else {
2405 // Must use this rather than serialization page in particular on Windows
2406 InterfaceSupport::serialize_memory(thread);
2407 }
2408 }
2409 }
2410
2411 if (SafepointSynchronize::do_call_back()) {
2412 // If we are safepointing, then block the caller which may not be
2413 // the same as the target thread (see above).
2414 SafepointSynchronize::block(curJT);
2415 }
2416
2417 if (thread->is_deopt_suspend()) {
2418 thread->clear_deopt_suspend();
2419 RegisterMap map(thread, false);
2420 frame f = thread->last_frame();
2421 while (f.id() != thread->must_deopt_id() && ! f.is_first_frame()) {
2422 f = f.sender(&map);
2423 }
2424 if (f.id() == thread->must_deopt_id()) {
2425 thread->clear_must_deopt_id();
2426 f.deoptimize(thread);
2427 } else {
2428 fatal("missed deoptimization!");
2429 }
2430 }
2431 }
2432
2433 // Slow path when the native==>VM/Java barriers detect a safepoint is in
2434 // progress or when _suspend_flags is non-zero.
2435 // Current thread needs to self-suspend if there is a suspend request and/or
2436 // block if a safepoint is in progress.
2437 // Also check for pending async exception (not including unsafe access error).
2438 // Note only the native==>VM/Java barriers can call this function and when
2439 // thread state is _thread_in_native_trans.
2440 void JavaThread::check_special_condition_for_native_trans(JavaThread *thread) {
2441 check_safepoint_and_suspend_for_native_trans(thread);
2442
2443 if (thread->has_async_exception()) {
2444 // We are in _thread_in_native_trans state, don't handle unsafe
2445 // access error since that may block.
2446 thread->check_and_handle_async_exceptions(false);
2447 }
2448 }
2449
2450 // This is a variant of the normal
2451 // check_special_condition_for_native_trans with slightly different
2452 // semantics for use by critical native wrappers. It does all the
2453 // normal checks but also performs the transition back into
2454 // thread_in_Java state. This is required so that critical natives
2455 // can potentially block and perform a GC if they are the last thread
2456 // exiting the GCLocker.
2457 void JavaThread::check_special_condition_for_native_trans_and_transition(JavaThread *thread) {
2458 check_special_condition_for_native_trans(thread);
2459
2460 // Finish the transition
2461 thread->set_thread_state(_thread_in_Java);
2462
2463 if (thread->do_critical_native_unlock()) {
2464 ThreadInVMfromJavaNoAsyncException tiv(thread);
2465 GCLocker::unlock_critical(thread);
2466 thread->clear_critical_native_unlock();
2467 }
2468 }
2469
2470 // We need to guarantee the Threads_lock here, since resumes are not
2471 // allowed during safepoint synchronization
2472 // Can only resume from an external suspension
2473 void JavaThread::java_resume() {
2474 assert_locked_or_safepoint(Threads_lock);
2475
2476 // Sanity check: thread is gone, has started exiting or the thread
2477 // was not externally suspended.
2478 if (!Threads::includes(this) || is_exiting() || !is_external_suspend()) {
2479 return;
2480 }
2481
2482 MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2483
2484 clear_external_suspend();
2485
2486 if (is_ext_suspended()) {
2487 clear_ext_suspended();
2488 SR_lock()->notify_all();
2489 }
2490 }
2491
2492 size_t JavaThread::_stack_red_zone_size = 0;
2493 size_t JavaThread::_stack_yellow_zone_size = 0;
2494 size_t JavaThread::_stack_reserved_zone_size = 0;
2495 size_t JavaThread::_stack_shadow_zone_size = 0;
2496
2497 void JavaThread::create_stack_guard_pages() {
2498 if (!os::uses_stack_guard_pages() || _stack_guard_state != stack_guard_unused) { return; }
2499 address low_addr = stack_end();
2500 size_t len = stack_guard_zone_size();
2501
2502 int must_commit = os::must_commit_stack_guard_pages();
2503 // warning("Guarding at " PTR_FORMAT " for len " SIZE_FORMAT "\n", low_addr, len);
2504
2505 if (must_commit && !os::create_stack_guard_pages((char *) low_addr, len)) {
2506 log_warning(os, thread)("Attempt to allocate stack guard pages failed.");
2507 return;
2508 }
2509
2510 if (os::guard_memory((char *) low_addr, len)) {
2511 _stack_guard_state = stack_guard_enabled;
2512 } else {
2513 log_warning(os, thread)("Attempt to protect stack guard pages failed ("
2514 PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
2515 if (os::uncommit_memory((char *) low_addr, len)) {
2516 log_warning(os, thread)("Attempt to deallocate stack guard pages failed.");
2517 }
2518 return;
2519 }
2520
2521 log_debug(os, thread)("Thread " UINTX_FORMAT " stack guard pages activated: "
2522 PTR_FORMAT "-" PTR_FORMAT ".",
2523 os::current_thread_id(), p2i(low_addr), p2i(low_addr + len));
2524 }
2525
2526 void JavaThread::remove_stack_guard_pages() {
2527 assert(Thread::current() == this, "from different thread");
2528 if (_stack_guard_state == stack_guard_unused) return;
2529 address low_addr = stack_end();
2530 size_t len = stack_guard_zone_size();
2531
2532 if (os::must_commit_stack_guard_pages()) {
2533 if (os::remove_stack_guard_pages((char *) low_addr, len)) {
2534 _stack_guard_state = stack_guard_unused;
2535 } else {
2536 log_warning(os, thread)("Attempt to deallocate stack guard pages failed ("
2537 PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
2538 return;
2539 }
2540 } else {
2541 if (_stack_guard_state == stack_guard_unused) return;
2542 if (os::unguard_memory((char *) low_addr, len)) {
2543 _stack_guard_state = stack_guard_unused;
2544 } else {
2545 log_warning(os, thread)("Attempt to unprotect stack guard pages failed ("
2546 PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
2547 return;
2548 }
2549 }
2550
2551 log_debug(os, thread)("Thread " UINTX_FORMAT " stack guard pages removed: "
2552 PTR_FORMAT "-" PTR_FORMAT ".",
2553 os::current_thread_id(), p2i(low_addr), p2i(low_addr + len));
2554 }
2555
2556 void JavaThread::enable_stack_reserved_zone() {
2557 assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2558 assert(_stack_guard_state != stack_guard_enabled, "already enabled");
2559
2560 // The base notation is from the stack's point of view, growing downward.
2561 // We need to adjust it to work correctly with guard_memory()
2562 address base = stack_reserved_zone_base() - stack_reserved_zone_size();
2563
2564 guarantee(base < stack_base(),"Error calculating stack reserved zone");
2565 guarantee(base < os::current_stack_pointer(),"Error calculating stack reserved zone");
2566
2567 if (os::guard_memory((char *) base, stack_reserved_zone_size())) {
2568 _stack_guard_state = stack_guard_enabled;
2569 } else {
2570 warning("Attempt to guard stack reserved zone failed.");
2571 }
2572 enable_register_stack_guard();
2573 }
2574
2575 void JavaThread::disable_stack_reserved_zone() {
2576 assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2577 assert(_stack_guard_state != stack_guard_reserved_disabled, "already disabled");
2578
2579 // Simply return if called for a thread that does not use guard pages.
2580 if (_stack_guard_state == stack_guard_unused) return;
2581
2582 // The base notation is from the stack's point of view, growing downward.
2583 // We need to adjust it to work correctly with guard_memory()
2584 address base = stack_reserved_zone_base() - stack_reserved_zone_size();
2585
2586 if (os::unguard_memory((char *)base, stack_reserved_zone_size())) {
2587 _stack_guard_state = stack_guard_reserved_disabled;
2588 } else {
2589 warning("Attempt to unguard stack reserved zone failed.");
2590 }
2591 disable_register_stack_guard();
2592 }
2593
2594 void JavaThread::enable_stack_yellow_reserved_zone() {
2595 assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2596 assert(_stack_guard_state != stack_guard_enabled, "already enabled");
2597
2598 // The base notation is from the stacks point of view, growing downward.
2599 // We need to adjust it to work correctly with guard_memory()
2600 address base = stack_red_zone_base();
2601
2602 guarantee(base < stack_base(), "Error calculating stack yellow zone");
2603 guarantee(base < os::current_stack_pointer(), "Error calculating stack yellow zone");
2604
2605 if (os::guard_memory((char *) base, stack_yellow_reserved_zone_size())) {
2606 _stack_guard_state = stack_guard_enabled;
2607 } else {
2608 warning("Attempt to guard stack yellow zone failed.");
2609 }
2610 enable_register_stack_guard();
2611 }
2612
2613 void JavaThread::disable_stack_yellow_reserved_zone() {
2614 assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2615 assert(_stack_guard_state != stack_guard_yellow_reserved_disabled, "already disabled");
2616
2617 // Simply return if called for a thread that does not use guard pages.
2618 if (_stack_guard_state == stack_guard_unused) return;
2619
2620 // The base notation is from the stacks point of view, growing downward.
2621 // We need to adjust it to work correctly with guard_memory()
2622 address base = stack_red_zone_base();
2623
2624 if (os::unguard_memory((char *)base, stack_yellow_reserved_zone_size())) {
2625 _stack_guard_state = stack_guard_yellow_reserved_disabled;
2626 } else {
2627 warning("Attempt to unguard stack yellow zone failed.");
2628 }
2629 disable_register_stack_guard();
2630 }
2631
2632 void JavaThread::enable_stack_red_zone() {
2633 // The base notation is from the stacks point of view, growing downward.
2634 // We need to adjust it to work correctly with guard_memory()
2635 assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2636 address base = stack_red_zone_base() - stack_red_zone_size();
2637
2638 guarantee(base < stack_base(), "Error calculating stack red zone");
2639 guarantee(base < os::current_stack_pointer(), "Error calculating stack red zone");
2640
2641 if (!os::guard_memory((char *) base, stack_red_zone_size())) {
2642 warning("Attempt to guard stack red zone failed.");
2643 }
2644 }
2645
2646 void JavaThread::disable_stack_red_zone() {
2647 // The base notation is from the stacks point of view, growing downward.
2648 // We need to adjust it to work correctly with guard_memory()
2649 assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2650 address base = stack_red_zone_base() - stack_red_zone_size();
2651 if (!os::unguard_memory((char *)base, stack_red_zone_size())) {
2652 warning("Attempt to unguard stack red zone failed.");
2653 }
2654 }
2655
2656 void JavaThread::frames_do(void f(frame*, const RegisterMap* map)) {
2657 // ignore is there is no stack
2658 if (!has_last_Java_frame()) return;
2659 // traverse the stack frames. Starts from top frame.
2660 for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2661 frame* fr = fst.current();
2662 f(fr, fst.register_map());
2663 }
2664 }
2665
2666
2667 #ifndef PRODUCT
2668 // Deoptimization
2669 // Function for testing deoptimization
2670 void JavaThread::deoptimize() {
2671 // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2672 StackFrameStream fst(this, UseBiasedLocking);
2673 bool deopt = false; // Dump stack only if a deopt actually happens.
2674 bool only_at = strlen(DeoptimizeOnlyAt) > 0;
2675 // Iterate over all frames in the thread and deoptimize
2676 for (; !fst.is_done(); fst.next()) {
2677 if (fst.current()->can_be_deoptimized()) {
2678
2679 if (only_at) {
2680 // Deoptimize only at particular bcis. DeoptimizeOnlyAt
2681 // consists of comma or carriage return separated numbers so
2682 // search for the current bci in that string.
2683 address pc = fst.current()->pc();
2684 nmethod* nm = (nmethod*) fst.current()->cb();
2685 ScopeDesc* sd = nm->scope_desc_at(pc);
2686 char buffer[8];
2687 jio_snprintf(buffer, sizeof(buffer), "%d", sd->bci());
2688 size_t len = strlen(buffer);
2689 const char * found = strstr(DeoptimizeOnlyAt, buffer);
2690 while (found != NULL) {
2691 if ((found[len] == ',' || found[len] == '\n' || found[len] == '\0') &&
2692 (found == DeoptimizeOnlyAt || found[-1] == ',' || found[-1] == '\n')) {
2693 // Check that the bci found is bracketed by terminators.
2694 break;
2695 }
2696 found = strstr(found + 1, buffer);
2697 }
2698 if (!found) {
2699 continue;
2700 }
2701 }
2702
2703 if (DebugDeoptimization && !deopt) {
2704 deopt = true; // One-time only print before deopt
2705 tty->print_cr("[BEFORE Deoptimization]");
2706 trace_frames();
2707 trace_stack();
2708 }
2709 Deoptimization::deoptimize(this, *fst.current(), fst.register_map());
2710 }
2711 }
2712
2713 if (DebugDeoptimization && deopt) {
2714 tty->print_cr("[AFTER Deoptimization]");
2715 trace_frames();
2716 }
2717 }
2718
2719
2720 // Make zombies
2721 void JavaThread::make_zombies() {
2722 for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2723 if (fst.current()->can_be_deoptimized()) {
2724 // it is a Java nmethod
2725 nmethod* nm = CodeCache::find_nmethod(fst.current()->pc());
2726 nm->make_not_entrant();
2727 }
2728 }
2729 }
2730 #endif // PRODUCT
2731
2732
2733 void JavaThread::deoptimized_wrt_marked_nmethods() {
2734 if (!has_last_Java_frame()) return;
2735 // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2736 StackFrameStream fst(this, UseBiasedLocking);
2737 for (; !fst.is_done(); fst.next()) {
2738 if (fst.current()->should_be_deoptimized()) {
2739 Deoptimization::deoptimize(this, *fst.current(), fst.register_map());
2740 }
2741 }
2742 }
2743
2744
2745 // If the caller is a NamedThread, then remember, in the current scope,
2746 // the given JavaThread in its _processed_thread field.
2747 class RememberProcessedThread: public StackObj {
2748 NamedThread* _cur_thr;
2749 public:
2750 RememberProcessedThread(JavaThread* jthr) {
2751 Thread* thread = Thread::current();
2752 if (thread->is_Named_thread()) {
2753 _cur_thr = (NamedThread *)thread;
2754 _cur_thr->set_processed_thread(jthr);
2755 } else {
2756 _cur_thr = NULL;
2757 }
2758 }
2759
2760 ~RememberProcessedThread() {
2761 if (_cur_thr) {
2762 _cur_thr->set_processed_thread(NULL);
2763 }
2764 }
2765 };
2766
2767 void JavaThread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
2768 // Verify that the deferred card marks have been flushed.
2769 assert(deferred_card_mark().is_empty(), "Should be empty during GC");
2770
2771 // The ThreadProfiler oops_do is done from FlatProfiler::oops_do
2772 // since there may be more than one thread using each ThreadProfiler.
2773
2774 // Traverse the GCHandles
2775 Thread::oops_do(f, cf);
2776
2777 JVMCI_ONLY(f->do_oop((oop*)&_pending_failed_speculation);)
2778
2779 assert((!has_last_Java_frame() && java_call_counter() == 0) ||
2780 (has_last_Java_frame() && java_call_counter() > 0), "wrong java_sp info!");
2781
2782 if (has_last_Java_frame()) {
2783 // Record JavaThread to GC thread
2784 RememberProcessedThread rpt(this);
2785
2786 // Traverse the privileged stack
2787 if (_privileged_stack_top != NULL) {
2788 _privileged_stack_top->oops_do(f);
2789 }
2790
2791 // traverse the registered growable array
2792 if (_array_for_gc != NULL) {
2793 for (int index = 0; index < _array_for_gc->length(); index++) {
2794 f->do_oop(_array_for_gc->adr_at(index));
2795 }
2796 }
2797
2798 // Traverse the monitor chunks
2799 for (MonitorChunk* chunk = monitor_chunks(); chunk != NULL; chunk = chunk->next()) {
2800 chunk->oops_do(f);
2801 }
2802
2803 // Traverse the execution stack
2804 for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2805 fst.current()->oops_do(f, cf, fst.register_map());
2806 }
2807 }
2808
2809 // callee_target is never live across a gc point so NULL it here should
2810 // it still contain a methdOop.
2811
2812 set_callee_target(NULL);
2813
2814 assert(vframe_array_head() == NULL, "deopt in progress at a safepoint!");
2815 // If we have deferred set_locals there might be oops waiting to be
2816 // written
2817 GrowableArray<jvmtiDeferredLocalVariableSet*>* list = deferred_locals();
2818 if (list != NULL) {
2819 for (int i = 0; i < list->length(); i++) {
2820 list->at(i)->oops_do(f);
2821 }
2822 }
2823
2824 // Traverse instance variables at the end since the GC may be moving things
2825 // around using this function
2826 f->do_oop((oop*) &_threadObj);
2827 f->do_oop((oop*) &_vm_result);
2828 f->do_oop((oop*) &_exception_oop);
2829 f->do_oop((oop*) &_pending_async_exception);
2830
2831 if (jvmti_thread_state() != NULL) {
2832 jvmti_thread_state()->oops_do(f);
2833 }
2834 }
2835
2836 void JavaThread::nmethods_do(CodeBlobClosure* cf) {
2837 assert((!has_last_Java_frame() && java_call_counter() == 0) ||
2838 (has_last_Java_frame() && java_call_counter() > 0), "wrong java_sp info!");
2839
2840 if (has_last_Java_frame()) {
2841 // Traverse the execution stack
2842 for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2843 fst.current()->nmethods_do(cf);
2844 }
2845 }
2846 }
2847
2848 void JavaThread::metadata_do(void f(Metadata*)) {
2849 if (has_last_Java_frame()) {
2850 // Traverse the execution stack to call f() on the methods in the stack
2851 for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2852 fst.current()->metadata_do(f);
2853 }
2854 } else if (is_Compiler_thread()) {
2855 // need to walk ciMetadata in current compile tasks to keep alive.
2856 CompilerThread* ct = (CompilerThread*)this;
2857 if (ct->env() != NULL) {
2858 ct->env()->metadata_do(f);
2859 }
2860 if (ct->task() != NULL) {
2861 ct->task()->metadata_do(f);
2862 }
2863 }
2864 }
2865
2866 // Printing
2867 const char* _get_thread_state_name(JavaThreadState _thread_state) {
2868 switch (_thread_state) {
2869 case _thread_uninitialized: return "_thread_uninitialized";
2870 case _thread_new: return "_thread_new";
2871 case _thread_new_trans: return "_thread_new_trans";
2872 case _thread_in_native: return "_thread_in_native";
2873 case _thread_in_native_trans: return "_thread_in_native_trans";
2874 case _thread_in_vm: return "_thread_in_vm";
2875 case _thread_in_vm_trans: return "_thread_in_vm_trans";
2876 case _thread_in_Java: return "_thread_in_Java";
2877 case _thread_in_Java_trans: return "_thread_in_Java_trans";
2878 case _thread_blocked: return "_thread_blocked";
2879 case _thread_blocked_trans: return "_thread_blocked_trans";
2880 default: return "unknown thread state";
2881 }
2882 }
2883
2884 #ifndef PRODUCT
2885 void JavaThread::print_thread_state_on(outputStream *st) const {
2886 st->print_cr(" JavaThread state: %s", _get_thread_state_name(_thread_state));
2887 };
2888 void JavaThread::print_thread_state() const {
2889 print_thread_state_on(tty);
2890 }
2891 #endif // PRODUCT
2892
2893 // Called by Threads::print() for VM_PrintThreads operation
2894 void JavaThread::print_on(outputStream *st) const {
2895 st->print_raw("\"");
2896 st->print_raw(get_thread_name());
2897 st->print_raw("\" ");
2898 oop thread_oop = threadObj();
2899 if (thread_oop != NULL) {
2900 st->print("#" INT64_FORMAT " ", java_lang_Thread::thread_id(thread_oop));
2901 if (java_lang_Thread::is_daemon(thread_oop)) st->print("daemon ");
2902 st->print("prio=%d ", java_lang_Thread::priority(thread_oop));
2903 }
2904 Thread::print_on(st);
2905 // print guess for valid stack memory region (assume 4K pages); helps lock debugging
2906 st->print_cr("[" INTPTR_FORMAT "]", (intptr_t)last_Java_sp() & ~right_n_bits(12));
2907 if (thread_oop != NULL) {
2908 st->print_cr(" java.lang.Thread.State: %s", java_lang_Thread::thread_status_name(thread_oop));
2909 }
2910 #ifndef PRODUCT
2911 print_thread_state_on(st);
2912 _safepoint_state->print_on(st);
2913 #endif // PRODUCT
2914 if (is_Compiler_thread()) {
2915 CompilerThread* ct = (CompilerThread*)this;
2916 if (ct->task() != NULL) {
2917 st->print(" Compiling: ");
2918 ct->task()->print(st, NULL, true, false);
2919 } else {
2920 st->print(" No compile task");
2921 }
2922 st->cr();
2923 }
2924 }
2925
2926 void JavaThread::print_name_on_error(outputStream* st, char *buf, int buflen) const {
2927 st->print("%s", get_thread_name_string(buf, buflen));
2928 }
2929
2930 // Called by fatal error handler. The difference between this and
2931 // JavaThread::print() is that we can't grab lock or allocate memory.
2932 void JavaThread::print_on_error(outputStream* st, char *buf, int buflen) const {
2933 st->print("JavaThread \"%s\"", get_thread_name_string(buf, buflen));
2934 oop thread_obj = threadObj();
2935 if (thread_obj != NULL) {
2936 if (java_lang_Thread::is_daemon(thread_obj)) st->print(" daemon");
2937 }
2938 st->print(" [");
2939 st->print("%s", _get_thread_state_name(_thread_state));
2940 if (osthread()) {
2941 st->print(", id=%d", osthread()->thread_id());
2942 }
2943 st->print(", stack(" PTR_FORMAT "," PTR_FORMAT ")",
2944 p2i(stack_end()), p2i(stack_base()));
2945 st->print("]");
2946 return;
2947 }
2948
2949 // Verification
2950
2951 static void frame_verify(frame* f, const RegisterMap *map) { f->verify(map); }
2952
2953 void JavaThread::verify() {
2954 // Verify oops in the thread.
2955 oops_do(&VerifyOopClosure::verify_oop, NULL);
2956
2957 // Verify the stack frames.
2958 frames_do(frame_verify);
2959 }
2960
2961 // CR 6300358 (sub-CR 2137150)
2962 // Most callers of this method assume that it can't return NULL but a
2963 // thread may not have a name whilst it is in the process of attaching to
2964 // the VM - see CR 6412693, and there are places where a JavaThread can be
2965 // seen prior to having it's threadObj set (eg JNI attaching threads and
2966 // if vm exit occurs during initialization). These cases can all be accounted
2967 // for such that this method never returns NULL.
2968 const char* JavaThread::get_thread_name() const {
2969 #ifdef ASSERT
2970 // early safepoints can hit while current thread does not yet have TLS
2971 if (!SafepointSynchronize::is_at_safepoint()) {
2972 Thread *cur = Thread::current();
2973 if (!(cur->is_Java_thread() && cur == this)) {
2974 // Current JavaThreads are allowed to get their own name without
2975 // the Threads_lock.
2976 assert_locked_or_safepoint(Threads_lock);
2977 }
2978 }
2979 #endif // ASSERT
2980 return get_thread_name_string();
2981 }
2982
2983 // Returns a non-NULL representation of this thread's name, or a suitable
2984 // descriptive string if there is no set name
2985 const char* JavaThread::get_thread_name_string(char* buf, int buflen) const {
2986 const char* name_str;
2987 oop thread_obj = threadObj();
2988 if (thread_obj != NULL) {
2989 oop name = java_lang_Thread::name(thread_obj);
2990 if (name != NULL) {
2991 if (buf == NULL) {
2992 name_str = java_lang_String::as_utf8_string(name);
2993 } else {
2994 name_str = java_lang_String::as_utf8_string(name, buf, buflen);
2995 }
2996 } else if (is_attaching_via_jni()) { // workaround for 6412693 - see 6404306
2997 name_str = "<no-name - thread is attaching>";
2998 } else {
2999 name_str = Thread::name();
3000 }
3001 } else {
3002 name_str = Thread::name();
3003 }
3004 assert(name_str != NULL, "unexpected NULL thread name");
3005 return name_str;
3006 }
3007
3008
3009 const char* JavaThread::get_threadgroup_name() const {
3010 debug_only(if (JavaThread::current() != this) assert_locked_or_safepoint(Threads_lock);)
3011 oop thread_obj = threadObj();
3012 if (thread_obj != NULL) {
3013 oop thread_group = java_lang_Thread::threadGroup(thread_obj);
3014 if (thread_group != NULL) {
3015 // ThreadGroup.name can be null
3016 return java_lang_ThreadGroup::name(thread_group);
3017 }
3018 }
3019 return NULL;
3020 }
3021
3022 const char* JavaThread::get_parent_name() const {
3023 debug_only(if (JavaThread::current() != this) assert_locked_or_safepoint(Threads_lock);)
3024 oop thread_obj = threadObj();
3025 if (thread_obj != NULL) {
3026 oop thread_group = java_lang_Thread::threadGroup(thread_obj);
3027 if (thread_group != NULL) {
3028 oop parent = java_lang_ThreadGroup::parent(thread_group);
3029 if (parent != NULL) {
3030 // ThreadGroup.name can be null
3031 return java_lang_ThreadGroup::name(parent);
3032 }
3033 }
3034 }
3035 return NULL;
3036 }
3037
3038 ThreadPriority JavaThread::java_priority() const {
3039 oop thr_oop = threadObj();
3040 if (thr_oop == NULL) return NormPriority; // Bootstrapping
3041 ThreadPriority priority = java_lang_Thread::priority(thr_oop);
3042 assert(MinPriority <= priority && priority <= MaxPriority, "sanity check");
3043 return priority;
3044 }
3045
3046 void JavaThread::prepare(jobject jni_thread, ThreadPriority prio) {
3047
3048 assert(Threads_lock->owner() == Thread::current(), "must have threads lock");
3049 // Link Java Thread object <-> C++ Thread
3050
3051 // Get the C++ thread object (an oop) from the JNI handle (a jthread)
3052 // and put it into a new Handle. The Handle "thread_oop" can then
3053 // be used to pass the C++ thread object to other methods.
3054
3055 // Set the Java level thread object (jthread) field of the
3056 // new thread (a JavaThread *) to C++ thread object using the
3057 // "thread_oop" handle.
3058
3059 // Set the thread field (a JavaThread *) of the
3060 // oop representing the java_lang_Thread to the new thread (a JavaThread *).
3061
3062 Handle thread_oop(Thread::current(),
3063 JNIHandles::resolve_non_null(jni_thread));
3064 assert(InstanceKlass::cast(thread_oop->klass())->is_linked(),
3065 "must be initialized");
3066 set_threadObj(thread_oop());
3067 java_lang_Thread::set_thread(thread_oop(), this);
3068
3069 if (prio == NoPriority) {
3070 prio = java_lang_Thread::priority(thread_oop());
3071 assert(prio != NoPriority, "A valid priority should be present");
3072 }
3073
3074 // Push the Java priority down to the native thread; needs Threads_lock
3075 Thread::set_priority(this, prio);
3076
3077 prepare_ext();
3078
3079 // Add the new thread to the Threads list and set it in motion.
3080 // We must have threads lock in order to call Threads::add.
3081 // It is crucial that we do not block before the thread is
3082 // added to the Threads list for if a GC happens, then the java_thread oop
3083 // will not be visited by GC.
3084 Threads::add(this);
3085 }
3086
3087 oop JavaThread::current_park_blocker() {
3088 // Support for JSR-166 locks
3089 oop thread_oop = threadObj();
3090 if (thread_oop != NULL &&
3091 JDK_Version::current().supports_thread_park_blocker()) {
3092 return java_lang_Thread::park_blocker(thread_oop);
3093 }
3094 return NULL;
3095 }
3096
3097
3098 void JavaThread::print_stack_on(outputStream* st) {
3099 if (!has_last_Java_frame()) return;
3100 ResourceMark rm;
3101 HandleMark hm;
3102
3103 RegisterMap reg_map(this);
3104 vframe* start_vf = last_java_vframe(®_map);
3105 int count = 0;
3106 for (vframe* f = start_vf; f; f = f->sender()) {
3107 if (f->is_java_frame()) {
3108 javaVFrame* jvf = javaVFrame::cast(f);
3109 java_lang_Throwable::print_stack_element(st, jvf->method(), jvf->bci());
3110
3111 // Print out lock information
3112 if (JavaMonitorsInStackTrace) {
3113 jvf->print_lock_info_on(st, count);
3114 }
3115 } else {
3116 // Ignore non-Java frames
3117 }
3118
3119 // Bail-out case for too deep stacks
3120 count++;
3121 if (MaxJavaStackTraceDepth == count) return;
3122 }
3123 }
3124
3125
3126 // JVMTI PopFrame support
3127 void JavaThread::popframe_preserve_args(ByteSize size_in_bytes, void* start) {
3128 assert(_popframe_preserved_args == NULL, "should not wipe out old PopFrame preserved arguments");
3129 if (in_bytes(size_in_bytes) != 0) {
3130 _popframe_preserved_args = NEW_C_HEAP_ARRAY(char, in_bytes(size_in_bytes), mtThread);
3131 _popframe_preserved_args_size = in_bytes(size_in_bytes);
3132 Copy::conjoint_jbytes(start, _popframe_preserved_args, _popframe_preserved_args_size);
3133 }
3134 }
3135
3136 void* JavaThread::popframe_preserved_args() {
3137 return _popframe_preserved_args;
3138 }
3139
3140 ByteSize JavaThread::popframe_preserved_args_size() {
3141 return in_ByteSize(_popframe_preserved_args_size);
3142 }
3143
3144 WordSize JavaThread::popframe_preserved_args_size_in_words() {
3145 int sz = in_bytes(popframe_preserved_args_size());
3146 assert(sz % wordSize == 0, "argument size must be multiple of wordSize");
3147 return in_WordSize(sz / wordSize);
3148 }
3149
3150 void JavaThread::popframe_free_preserved_args() {
3151 assert(_popframe_preserved_args != NULL, "should not free PopFrame preserved arguments twice");
3152 FREE_C_HEAP_ARRAY(char, (char*) _popframe_preserved_args);
3153 _popframe_preserved_args = NULL;
3154 _popframe_preserved_args_size = 0;
3155 }
3156
3157 #ifndef PRODUCT
3158
3159 void JavaThread::trace_frames() {
3160 tty->print_cr("[Describe stack]");
3161 int frame_no = 1;
3162 for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
3163 tty->print(" %d. ", frame_no++);
3164 fst.current()->print_value_on(tty, this);
3165 tty->cr();
3166 }
3167 }
3168
3169 class PrintAndVerifyOopClosure: public OopClosure {
3170 protected:
3171 template <class T> inline void do_oop_work(T* p) {
3172 oop obj = oopDesc::load_decode_heap_oop(p);
3173 if (obj == NULL) return;
3174 tty->print(INTPTR_FORMAT ": ", p2i(p));
3175 if (obj->is_oop_or_null()) {
3176 if (obj->is_objArray()) {
3177 tty->print_cr("valid objArray: " INTPTR_FORMAT, p2i(obj));
3178 } else {
3179 obj->print();
3180 }
3181 } else {
3182 tty->print_cr("invalid oop: " INTPTR_FORMAT, p2i(obj));
3183 }
3184 tty->cr();
3185 }
3186 public:
3187 virtual void do_oop(oop* p) { do_oop_work(p); }
3188 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3189 };
3190
3191
3192 static void oops_print(frame* f, const RegisterMap *map) {
3193 PrintAndVerifyOopClosure print;
3194 f->print_value();
3195 f->oops_do(&print, NULL, (RegisterMap*)map);
3196 }
3197
3198 // Print our all the locations that contain oops and whether they are
3199 // valid or not. This useful when trying to find the oldest frame
3200 // where an oop has gone bad since the frame walk is from youngest to
3201 // oldest.
3202 void JavaThread::trace_oops() {
3203 tty->print_cr("[Trace oops]");
3204 frames_do(oops_print);
3205 }
3206
3207
3208 #ifdef ASSERT
3209 // Print or validate the layout of stack frames
3210 void JavaThread::print_frame_layout(int depth, bool validate_only) {
3211 ResourceMark rm;
3212 PRESERVE_EXCEPTION_MARK;
3213 FrameValues values;
3214 int frame_no = 0;
3215 for (StackFrameStream fst(this, false); !fst.is_done(); fst.next()) {
3216 fst.current()->describe(values, ++frame_no);
3217 if (depth == frame_no) break;
3218 }
3219 if (validate_only) {
3220 values.validate();
3221 } else {
3222 tty->print_cr("[Describe stack layout]");
3223 values.print(this);
3224 }
3225 }
3226 #endif
3227
3228 void JavaThread::trace_stack_from(vframe* start_vf) {
3229 ResourceMark rm;
3230 int vframe_no = 1;
3231 for (vframe* f = start_vf; f; f = f->sender()) {
3232 if (f->is_java_frame()) {
3233 javaVFrame::cast(f)->print_activation(vframe_no++);
3234 } else {
3235 f->print();
3236 }
3237 if (vframe_no > StackPrintLimit) {
3238 tty->print_cr("...<more frames>...");
3239 return;
3240 }
3241 }
3242 }
3243
3244
3245 void JavaThread::trace_stack() {
3246 if (!has_last_Java_frame()) return;
3247 ResourceMark rm;
3248 HandleMark hm;
3249 RegisterMap reg_map(this);
3250 trace_stack_from(last_java_vframe(®_map));
3251 }
3252
3253
3254 #endif // PRODUCT
3255
3256
3257 javaVFrame* JavaThread::last_java_vframe(RegisterMap *reg_map) {
3258 assert(reg_map != NULL, "a map must be given");
3259 frame f = last_frame();
3260 for (vframe* vf = vframe::new_vframe(&f, reg_map, this); vf; vf = vf->sender()) {
3261 if (vf->is_java_frame()) return javaVFrame::cast(vf);
3262 }
3263 return NULL;
3264 }
3265
3266
3267 Klass* JavaThread::security_get_caller_class(int depth) {
3268 vframeStream vfst(this);
3269 vfst.security_get_caller_frame(depth);
3270 if (!vfst.at_end()) {
3271 return vfst.method()->method_holder();
3272 }
3273 return NULL;
3274 }
3275
3276 static void compiler_thread_entry(JavaThread* thread, TRAPS) {
3277 assert(thread->is_Compiler_thread(), "must be compiler thread");
3278 CompileBroker::compiler_thread_loop();
3279 }
3280
3281 static void sweeper_thread_entry(JavaThread* thread, TRAPS) {
3282 NMethodSweeper::sweeper_loop();
3283 }
3284
3285 // Create a CompilerThread
3286 CompilerThread::CompilerThread(CompileQueue* queue,
3287 CompilerCounters* counters)
3288 : JavaThread(&compiler_thread_entry) {
3289 _env = NULL;
3290 _log = NULL;
3291 _task = NULL;
3292 _queue = queue;
3293 _counters = counters;
3294 _buffer_blob = NULL;
3295 _compiler = NULL;
3296
3297 #ifndef PRODUCT
3298 _ideal_graph_printer = NULL;
3299 #endif
3300 }
3301
3302 bool CompilerThread::can_call_java() const {
3303 return _compiler != NULL && _compiler->is_jvmci();
3304 }
3305
3306 // Create sweeper thread
3307 CodeCacheSweeperThread::CodeCacheSweeperThread()
3308 : JavaThread(&sweeper_thread_entry) {
3309 _scanned_compiled_method = NULL;
3310 }
3311
3312 void CodeCacheSweeperThread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
3313 JavaThread::oops_do(f, cf);
3314 if (_scanned_compiled_method != NULL && cf != NULL) {
3315 // Safepoints can occur when the sweeper is scanning an nmethod so
3316 // process it here to make sure it isn't unloaded in the middle of
3317 // a scan.
3318 cf->do_code_blob(_scanned_compiled_method);
3319 }
3320 }
3321
3322 void CodeCacheSweeperThread::nmethods_do(CodeBlobClosure* cf) {
3323 JavaThread::nmethods_do(cf);
3324 if (_scanned_compiled_method != NULL && cf != NULL) {
3325 // Safepoints can occur when the sweeper is scanning an nmethod so
3326 // process it here to make sure it isn't unloaded in the middle of
3327 // a scan.
3328 cf->do_code_blob(_scanned_compiled_method);
3329 }
3330 }
3331
3332
3333 // ======= Threads ========
3334
3335 // The Threads class links together all active threads, and provides
3336 // operations over all threads. It is protected by its own Mutex
3337 // lock, which is also used in other contexts to protect thread
3338 // operations from having the thread being operated on from exiting
3339 // and going away unexpectedly (e.g., safepoint synchronization)
3340
3341 JavaThread* Threads::_thread_list = NULL;
3342 int Threads::_number_of_threads = 0;
3343 int Threads::_number_of_non_daemon_threads = 0;
3344 int Threads::_return_code = 0;
3345 int Threads::_thread_claim_parity = 0;
3346 size_t JavaThread::_stack_size_at_create = 0;
3347 #ifdef ASSERT
3348 bool Threads::_vm_complete = false;
3349 #endif
3350
3351 // All JavaThreads
3352 #define ALL_JAVA_THREADS(X) for (JavaThread* X = _thread_list; X; X = X->next())
3353
3354 // All JavaThreads + all non-JavaThreads (i.e., every thread in the system)
3355 void Threads::threads_do(ThreadClosure* tc) {
3356 assert_locked_or_safepoint(Threads_lock);
3357 // ALL_JAVA_THREADS iterates through all JavaThreads
3358 ALL_JAVA_THREADS(p) {
3359 tc->do_thread(p);
3360 }
3361 // Someday we could have a table or list of all non-JavaThreads.
3362 // For now, just manually iterate through them.
3363 tc->do_thread(VMThread::vm_thread());
3364 Universe::heap()->gc_threads_do(tc);
3365 WatcherThread *wt = WatcherThread::watcher_thread();
3366 // Strictly speaking, the following NULL check isn't sufficient to make sure
3367 // the data for WatcherThread is still valid upon being examined. However,
3368 // considering that WatchThread terminates when the VM is on the way to
3369 // exit at safepoint, the chance of the above is extremely small. The right
3370 // way to prevent termination of WatcherThread would be to acquire
3371 // Terminator_lock, but we can't do that without violating the lock rank
3372 // checking in some cases.
3373 if (wt != NULL) {
3374 tc->do_thread(wt);
3375 }
3376
3377 // If CompilerThreads ever become non-JavaThreads, add them here
3378 }
3379
3380 // The system initialization in the library has three phases.
3381 //
3382 // Phase 1: java.lang.System class initialization
3383 // java.lang.System is a primordial class loaded and initialized
3384 // by the VM early during startup. java.lang.System.<clinit>
3385 // only does registerNatives and keeps the rest of the class
3386 // initialization work later until thread initialization completes.
3387 //
3388 // System.initPhase1 initializes the system properties, the static
3389 // fields in, out, and err. Set up java signal handlers, OS-specific
3390 // system settings, and thread group of the main thread.
3391 static void call_initPhase1(TRAPS) {
3392 Klass* klass = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
3393 JavaValue result(T_VOID);
3394 JavaCalls::call_static(&result, klass, vmSymbols::initPhase1_name(),
3395 vmSymbols::void_method_signature(), CHECK);
3396 }
3397
3398 // Phase 2. Module system initialization
3399 // This will initialize the module system. Only java.base classes
3400 // can be loaded until phase 2 completes.
3401 //
3402 // Call System.initPhase2 after the compiler initialization and jsr292
3403 // classes get initialized because module initialization runs a lot of java
3404 // code, that for performance reasons, should be compiled. Also, this will
3405 // enable the startup code to use lambda and other language features in this
3406 // phase and onward.
3407 //
3408 // After phase 2, The VM will begin search classes from -Xbootclasspath/a.
3409 static void call_initPhase2(TRAPS) {
3410 TraceTime timer("Phase2 initialization", TRACETIME_LOG(Info, module, startuptime));
3411
3412 Klass* klass = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
3413
3414 JavaValue result(T_INT);
3415 JavaCallArguments args;
3416 args.push_int(DisplayVMOutputToStderr);
3417 args.push_int(log_is_enabled(Debug, init)); // print stack trace if exception thrown
3418 JavaCalls::call_static(&result, klass, vmSymbols::initPhase2_name(),
3419 vmSymbols::boolean_boolean_int_signature(), &args, CHECK);
3420 if (result.get_jint() != JNI_OK) {
3421 vm_exit_during_initialization(); // no message or exception
3422 }
3423
3424 universe_post_module_init();
3425 }
3426
3427 // Phase 3. final setup - set security manager, system class loader and TCCL
3428 //
3429 // This will instantiate and set the security manager, set the system class
3430 // loader as well as the thread context class loader. The security manager
3431 // and system class loader may be a custom class loaded from -Xbootclasspath/a,
3432 // other modules or the application's classpath.
3433 static void call_initPhase3(TRAPS) {
3434 Klass* klass = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
3435 JavaValue result(T_VOID);
3436 JavaCalls::call_static(&result, klass, vmSymbols::initPhase3_name(),
3437 vmSymbols::void_method_signature(), CHECK);
3438 }
3439
3440 void Threads::initialize_java_lang_classes(JavaThread* main_thread, TRAPS) {
3441 TraceTime timer("Initialize java.lang classes", TRACETIME_LOG(Info, startuptime));
3442
3443 if (EagerXrunInit && Arguments::init_libraries_at_startup()) {
3444 create_vm_init_libraries();
3445 }
3446
3447 initialize_class(vmSymbols::java_lang_String(), CHECK);
3448
3449 // Inject CompactStrings value after the static initializers for String ran.
3450 java_lang_String::set_compact_strings(CompactStrings);
3451
3452 // Initialize java_lang.System (needed before creating the thread)
3453 initialize_class(vmSymbols::java_lang_System(), CHECK);
3454 // The VM creates & returns objects of this class. Make sure it's initialized.
3455 initialize_class(vmSymbols::java_lang_Class(), CHECK);
3456 initialize_class(vmSymbols::java_lang_ThreadGroup(), CHECK);
3457 Handle thread_group = create_initial_thread_group(CHECK);
3458 Universe::set_main_thread_group(thread_group());
3459 initialize_class(vmSymbols::java_lang_Thread(), CHECK);
3460 oop thread_object = create_initial_thread(thread_group, main_thread, CHECK);
3461 main_thread->set_threadObj(thread_object);
3462 // Set thread status to running since main thread has
3463 // been started and running.
3464 java_lang_Thread::set_thread_status(thread_object,
3465 java_lang_Thread::RUNNABLE);
3466
3467 // The VM creates objects of this class.
3468 initialize_class(vmSymbols::java_lang_Module(), CHECK);
3469
3470 // The VM preresolves methods to these classes. Make sure that they get initialized
3471 initialize_class(vmSymbols::java_lang_reflect_Method(), CHECK);
3472 initialize_class(vmSymbols::java_lang_ref_Finalizer(), CHECK);
3473
3474 // Phase 1 of the system initialization in the library, java.lang.System class initialization
3475 call_initPhase1(CHECK);
3476
3477 // get the Java runtime name after java.lang.System is initialized
3478 JDK_Version::set_runtime_name(get_java_runtime_name(THREAD));
3479 JDK_Version::set_runtime_version(get_java_runtime_version(THREAD));
3480
3481 // an instance of OutOfMemory exception has been allocated earlier
3482 initialize_class(vmSymbols::java_lang_OutOfMemoryError(), CHECK);
3483 initialize_class(vmSymbols::java_lang_NullPointerException(), CHECK);
3484 initialize_class(vmSymbols::java_lang_ClassCastException(), CHECK);
3485 initialize_class(vmSymbols::java_lang_ArrayStoreException(), CHECK);
3486 initialize_class(vmSymbols::java_lang_ArithmeticException(), CHECK);
3487 initialize_class(vmSymbols::java_lang_StackOverflowError(), CHECK);
3488 initialize_class(vmSymbols::java_lang_IllegalMonitorStateException(), CHECK);
3489 initialize_class(vmSymbols::java_lang_IllegalArgumentException(), CHECK);
3490 }
3491
3492 void Threads::initialize_jsr292_core_classes(TRAPS) {
3493 TraceTime timer("Initialize java.lang.invoke classes", TRACETIME_LOG(Info, startuptime));
3494
3495 initialize_class(vmSymbols::java_lang_invoke_MethodHandle(), CHECK);
3496 initialize_class(vmSymbols::java_lang_invoke_MemberName(), CHECK);
3497 initialize_class(vmSymbols::java_lang_invoke_MethodHandleNatives(), CHECK);
3498 }
3499
3500 jint Threads::create_vm(JavaVMInitArgs* args, bool* canTryAgain) {
3501 extern void JDK_Version_init();
3502
3503 // Preinitialize version info.
3504 VM_Version::early_initialize();
3505
3506 // Check version
3507 if (!is_supported_jni_version(args->version)) return JNI_EVERSION;
3508
3509 // Initialize library-based TLS
3510 ThreadLocalStorage::init();
3511
3512 // Initialize the output stream module
3513 ostream_init();
3514
3515 // Process java launcher properties.
3516 Arguments::process_sun_java_launcher_properties(args);
3517
3518 // Initialize the os module
3519 os::init();
3520
3521 // Record VM creation timing statistics
3522 TraceVmCreationTime create_vm_timer;
3523 create_vm_timer.start();
3524
3525 // Initialize system properties.
3526 Arguments::init_system_properties();
3527
3528 // So that JDK version can be used as a discriminator when parsing arguments
3529 JDK_Version_init();
3530
3531 // Update/Initialize System properties after JDK version number is known
3532 Arguments::init_version_specific_system_properties();
3533
3534 // Make sure to initialize log configuration *before* parsing arguments
3535 LogConfiguration::initialize(create_vm_timer.begin_time());
3536
3537 // Parse arguments
3538 jint parse_result = Arguments::parse(args);
3539 if (parse_result != JNI_OK) return parse_result;
3540
3541 os::init_before_ergo();
3542
3543 jint ergo_result = Arguments::apply_ergo();
3544 if (ergo_result != JNI_OK) return ergo_result;
3545
3546 // Final check of all ranges after ergonomics which may change values.
3547 if (!CommandLineFlagRangeList::check_ranges()) {
3548 return JNI_EINVAL;
3549 }
3550
3551 // Final check of all 'AfterErgo' constraints after ergonomics which may change values.
3552 bool constraint_result = CommandLineFlagConstraintList::check_constraints(CommandLineFlagConstraint::AfterErgo);
3553 if (!constraint_result) {
3554 return JNI_EINVAL;
3555 }
3556
3557 CommandLineFlagWriteableList::mark_startup();
3558
3559 if (PauseAtStartup) {
3560 os::pause();
3561 }
3562
3563 HOTSPOT_VM_INIT_BEGIN();
3564
3565 // Timing (must come after argument parsing)
3566 TraceTime timer("Create VM", TRACETIME_LOG(Info, startuptime));
3567
3568 // Initialize the os module after parsing the args
3569 jint os_init_2_result = os::init_2();
3570 if (os_init_2_result != JNI_OK) return os_init_2_result;
3571
3572 jint adjust_after_os_result = Arguments::adjust_after_os();
3573 if (adjust_after_os_result != JNI_OK) return adjust_after_os_result;
3574
3575 // Initialize output stream logging
3576 ostream_init_log();
3577
3578 // Convert -Xrun to -agentlib: if there is no JVM_OnLoad
3579 // Must be before create_vm_init_agents()
3580 if (Arguments::init_libraries_at_startup()) {
3581 convert_vm_init_libraries_to_agents();
3582 }
3583
3584 // Launch -agentlib/-agentpath and converted -Xrun agents
3585 if (Arguments::init_agents_at_startup()) {
3586 create_vm_init_agents();
3587 }
3588
3589 // Initialize Threads state
3590 _thread_list = NULL;
3591 _number_of_threads = 0;
3592 _number_of_non_daemon_threads = 0;
3593
3594 // Initialize global data structures and create system classes in heap
3595 vm_init_globals();
3596
3597 #if INCLUDE_JVMCI
3598 if (JVMCICounterSize > 0) {
3599 JavaThread::_jvmci_old_thread_counters = NEW_C_HEAP_ARRAY(jlong, JVMCICounterSize, mtInternal);
3600 memset(JavaThread::_jvmci_old_thread_counters, 0, sizeof(jlong) * JVMCICounterSize);
3601 } else {
3602 JavaThread::_jvmci_old_thread_counters = NULL;
3603 }
3604 #endif // INCLUDE_JVMCI
3605
3606 // Attach the main thread to this os thread
3607 JavaThread* main_thread = new JavaThread();
3608 main_thread->set_thread_state(_thread_in_vm);
3609 main_thread->initialize_thread_current();
3610 // must do this before set_active_handles
3611 main_thread->record_stack_base_and_size();
3612 main_thread->set_active_handles(JNIHandleBlock::allocate_block());
3613
3614 if (!main_thread->set_as_starting_thread()) {
3615 vm_shutdown_during_initialization(
3616 "Failed necessary internal allocation. Out of swap space");
3617 delete main_thread;
3618 *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
3619 return JNI_ENOMEM;
3620 }
3621
3622 // Enable guard page *after* os::create_main_thread(), otherwise it would
3623 // crash Linux VM, see notes in os_linux.cpp.
3624 main_thread->create_stack_guard_pages();
3625
3626 // Initialize Java-Level synchronization subsystem
3627 ObjectMonitor::Initialize();
3628
3629 // Initialize global modules
3630 jint status = init_globals();
3631 if (status != JNI_OK) {
3632 delete main_thread;
3633 *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
3634 return status;
3635 }
3636
3637 if (TRACE_INITIALIZE() != JNI_OK) {
3638 vm_exit_during_initialization("Failed to initialize tracing backend");
3639 }
3640
3641 // Should be done after the heap is fully created
3642 main_thread->cache_global_variables();
3643
3644 HandleMark hm;
3645
3646 { MutexLocker mu(Threads_lock);
3647 Threads::add(main_thread);
3648 }
3649
3650 // Any JVMTI raw monitors entered in onload will transition into
3651 // real raw monitor. VM is setup enough here for raw monitor enter.
3652 JvmtiExport::transition_pending_onload_raw_monitors();
3653
3654 // Create the VMThread
3655 { TraceTime timer("Start VMThread", TRACETIME_LOG(Info, startuptime));
3656
3657 VMThread::create();
3658 Thread* vmthread = VMThread::vm_thread();
3659
3660 if (!os::create_thread(vmthread, os::vm_thread)) {
3661 vm_exit_during_initialization("Cannot create VM thread. "
3662 "Out of system resources.");
3663 }
3664
3665 // Wait for the VM thread to become ready, and VMThread::run to initialize
3666 // Monitors can have spurious returns, must always check another state flag
3667 {
3668 MutexLocker ml(Notify_lock);
3669 os::start_thread(vmthread);
3670 while (vmthread->active_handles() == NULL) {
3671 Notify_lock->wait();
3672 }
3673 }
3674 }
3675
3676 assert(Universe::is_fully_initialized(), "not initialized");
3677 if (VerifyDuringStartup) {
3678 // Make sure we're starting with a clean slate.
3679 VM_Verify verify_op;
3680 VMThread::execute(&verify_op);
3681 }
3682
3683 Thread* THREAD = Thread::current();
3684
3685 // At this point, the Universe is initialized, but we have not executed
3686 // any byte code. Now is a good time (the only time) to dump out the
3687 // internal state of the JVM for sharing.
3688 if (DumpSharedSpaces) {
3689 MetaspaceShared::preload_and_dump(CHECK_JNI_ERR);
3690 ShouldNotReachHere();
3691 }
3692
3693 // Always call even when there are not JVMTI environments yet, since environments
3694 // may be attached late and JVMTI must track phases of VM execution
3695 JvmtiExport::enter_early_start_phase();
3696
3697 // Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
3698 JvmtiExport::post_early_vm_start();
3699
3700 initialize_java_lang_classes(main_thread, CHECK_JNI_ERR);
3701
3702 // We need this for ClassDataSharing - the initial vm.info property is set
3703 // with the default value of CDS "sharing" which may be reset through
3704 // command line options.
3705 reset_vm_info_property(CHECK_JNI_ERR);
3706
3707 quicken_jni_functions();
3708
3709 // No more stub generation allowed after that point.
3710 StubCodeDesc::freeze();
3711
3712 // Set flag that basic initialization has completed. Used by exceptions and various
3713 // debug stuff, that does not work until all basic classes have been initialized.
3714 set_init_completed();
3715
3716 LogConfiguration::post_initialize();
3717 Metaspace::post_initialize();
3718
3719 HOTSPOT_VM_INIT_END();
3720
3721 // record VM initialization completion time
3722 #if INCLUDE_MANAGEMENT
3723 Management::record_vm_init_completed();
3724 #endif // INCLUDE_MANAGEMENT
3725
3726 // Signal Dispatcher needs to be started before VMInit event is posted
3727 os::signal_init(CHECK_JNI_ERR);
3728
3729 // Start Attach Listener if +StartAttachListener or it can't be started lazily
3730 if (!DisableAttachMechanism) {
3731 AttachListener::vm_start();
3732 if (StartAttachListener || AttachListener::init_at_startup()) {
3733 AttachListener::init();
3734 }
3735 }
3736
3737 // Launch -Xrun agents
3738 // Must be done in the JVMTI live phase so that for backward compatibility the JDWP
3739 // back-end can launch with -Xdebug -Xrunjdwp.
3740 if (!EagerXrunInit && Arguments::init_libraries_at_startup()) {
3741 create_vm_init_libraries();
3742 }
3743
3744 if (CleanChunkPoolAsync) {
3745 Chunk::start_chunk_pool_cleaner_task();
3746 }
3747
3748 // initialize compiler(s)
3749 #if defined(COMPILER1) || defined(COMPILER2) || defined(SHARK) || INCLUDE_JVMCI
3750 CompileBroker::compilation_init(CHECK_JNI_ERR);
3751 #endif
3752
3753 // Pre-initialize some JSR292 core classes to avoid deadlock during class loading.
3754 // It is done after compilers are initialized, because otherwise compilations of
3755 // signature polymorphic MH intrinsics can be missed
3756 // (see SystemDictionary::find_method_handle_intrinsic).
3757 initialize_jsr292_core_classes(CHECK_JNI_ERR);
3758
3759 // This will initialize the module system. Only java.base classes can be
3760 // loaded until phase 2 completes
3761 call_initPhase2(CHECK_JNI_ERR);
3762
3763 // Always call even when there are not JVMTI environments yet, since environments
3764 // may be attached late and JVMTI must track phases of VM execution
3765 JvmtiExport::enter_start_phase();
3766
3767 // Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
3768 JvmtiExport::post_vm_start();
3769
3770 // Final system initialization including security manager and system class loader
3771 call_initPhase3(CHECK_JNI_ERR);
3772
3773 // cache the system class loader
3774 SystemDictionary::compute_java_system_loader(CHECK_(JNI_ERR));
3775
3776 #if INCLUDE_JVMCI
3777 if (EnableJVMCI) {
3778 // Initialize JVMCI eagerly if JVMCIPrintProperties is enabled.
3779 // The JVMCI Java initialization code will read this flag and
3780 // do the printing if it's set.
3781 bool init = JVMCIPrintProperties;
3782
3783 if (!init) {
3784 // 8145270: Force initialization of JVMCI runtime otherwise requests for blocking
3785 // compilations via JVMCI will not actually block until JVMCI is initialized.
3786 init = UseJVMCICompiler && (!UseInterpreter || !BackgroundCompilation);
3787 }
3788
3789 if (init) {
3790 JVMCIRuntime::force_initialization(CHECK_JNI_ERR);
3791 }
3792 }
3793 #endif
3794
3795 // Always call even when there are not JVMTI environments yet, since environments
3796 // may be attached late and JVMTI must track phases of VM execution
3797 JvmtiExport::enter_live_phase();
3798
3799 // Notify JVMTI agents that VM initialization is complete - nop if no agents.
3800 JvmtiExport::post_vm_initialized();
3801
3802 if (TRACE_START() != JNI_OK) {
3803 vm_exit_during_initialization("Failed to start tracing backend.");
3804 }
3805
3806 #if INCLUDE_MANAGEMENT
3807 Management::initialize(THREAD);
3808
3809 if (HAS_PENDING_EXCEPTION) {
3810 // management agent fails to start possibly due to
3811 // configuration problem and is responsible for printing
3812 // stack trace if appropriate. Simply exit VM.
3813 vm_exit(1);
3814 }
3815 #endif // INCLUDE_MANAGEMENT
3816
3817 if (Arguments::has_profile()) FlatProfiler::engage(main_thread, true);
3818 if (MemProfiling) MemProfiler::engage();
3819 StatSampler::engage();
3820 if (CheckJNICalls) JniPeriodicChecker::engage();
3821
3822 BiasedLocking::init();
3823
3824 #if INCLUDE_RTM_OPT
3825 RTMLockingCounters::init();
3826 #endif
3827
3828 if (JDK_Version::current().post_vm_init_hook_enabled()) {
3829 call_postVMInitHook(THREAD);
3830 // The Java side of PostVMInitHook.run must deal with all
3831 // exceptions and provide means of diagnosis.
3832 if (HAS_PENDING_EXCEPTION) {
3833 CLEAR_PENDING_EXCEPTION;
3834 }
3835 }
3836
3837 {
3838 MutexLocker ml(PeriodicTask_lock);
3839 // Make sure the WatcherThread can be started by WatcherThread::start()
3840 // or by dynamic enrollment.
3841 WatcherThread::make_startable();
3842 // Start up the WatcherThread if there are any periodic tasks
3843 // NOTE: All PeriodicTasks should be registered by now. If they
3844 // aren't, late joiners might appear to start slowly (we might
3845 // take a while to process their first tick).
3846 if (PeriodicTask::num_tasks() > 0) {
3847 WatcherThread::start();
3848 }
3849 }
3850
3851 create_vm_timer.end();
3852 #ifdef ASSERT
3853 _vm_complete = true;
3854 #endif
3855 return JNI_OK;
3856 }
3857
3858 // type for the Agent_OnLoad and JVM_OnLoad entry points
3859 extern "C" {
3860 typedef jint (JNICALL *OnLoadEntry_t)(JavaVM *, char *, void *);
3861 }
3862 // Find a command line agent library and return its entry point for
3863 // -agentlib: -agentpath: -Xrun
3864 // num_symbol_entries must be passed-in since only the caller knows the number of symbols in the array.
3865 static OnLoadEntry_t lookup_on_load(AgentLibrary* agent,
3866 const char *on_load_symbols[],
3867 size_t num_symbol_entries) {
3868 OnLoadEntry_t on_load_entry = NULL;
3869 void *library = NULL;
3870
3871 if (!agent->valid()) {
3872 char buffer[JVM_MAXPATHLEN];
3873 char ebuf[1024] = "";
3874 const char *name = agent->name();
3875 const char *msg = "Could not find agent library ";
3876
3877 // First check to see if agent is statically linked into executable
3878 if (os::find_builtin_agent(agent, on_load_symbols, num_symbol_entries)) {
3879 library = agent->os_lib();
3880 } else if (agent->is_absolute_path()) {
3881 library = os::dll_load(name, ebuf, sizeof ebuf);
3882 if (library == NULL) {
3883 const char *sub_msg = " in absolute path, with error: ";
3884 size_t len = strlen(msg) + strlen(name) + strlen(sub_msg) + strlen(ebuf) + 1;
3885 char *buf = NEW_C_HEAP_ARRAY(char, len, mtThread);
3886 jio_snprintf(buf, len, "%s%s%s%s", msg, name, sub_msg, ebuf);
3887 // If we can't find the agent, exit.
3888 vm_exit_during_initialization(buf, NULL);
3889 FREE_C_HEAP_ARRAY(char, buf);
3890 }
3891 } else {
3892 // Try to load the agent from the standard dll directory
3893 if (os::dll_build_name(buffer, sizeof(buffer), Arguments::get_dll_dir(),
3894 name)) {
3895 library = os::dll_load(buffer, ebuf, sizeof ebuf);
3896 }
3897 if (library == NULL) { // Try the local directory
3898 char ns[1] = {0};
3899 if (os::dll_build_name(buffer, sizeof(buffer), ns, name)) {
3900 library = os::dll_load(buffer, ebuf, sizeof ebuf);
3901 }
3902 if (library == NULL) {
3903 const char *sub_msg = " on the library path, with error: ";
3904 size_t len = strlen(msg) + strlen(name) + strlen(sub_msg) + strlen(ebuf) + 1;
3905 char *buf = NEW_C_HEAP_ARRAY(char, len, mtThread);
3906 jio_snprintf(buf, len, "%s%s%s%s", msg, name, sub_msg, ebuf);
3907 // If we can't find the agent, exit.
3908 vm_exit_during_initialization(buf, NULL);
3909 FREE_C_HEAP_ARRAY(char, buf);
3910 }
3911 }
3912 }
3913 agent->set_os_lib(library);
3914 agent->set_valid();
3915 }
3916
3917 // Find the OnLoad function.
3918 on_load_entry =
3919 CAST_TO_FN_PTR(OnLoadEntry_t, os::find_agent_function(agent,
3920 false,
3921 on_load_symbols,
3922 num_symbol_entries));
3923 return on_load_entry;
3924 }
3925
3926 // Find the JVM_OnLoad entry point
3927 static OnLoadEntry_t lookup_jvm_on_load(AgentLibrary* agent) {
3928 const char *on_load_symbols[] = JVM_ONLOAD_SYMBOLS;
3929 return lookup_on_load(agent, on_load_symbols, sizeof(on_load_symbols) / sizeof(char*));
3930 }
3931
3932 // Find the Agent_OnLoad entry point
3933 static OnLoadEntry_t lookup_agent_on_load(AgentLibrary* agent) {
3934 const char *on_load_symbols[] = AGENT_ONLOAD_SYMBOLS;
3935 return lookup_on_load(agent, on_load_symbols, sizeof(on_load_symbols) / sizeof(char*));
3936 }
3937
3938 // For backwards compatibility with -Xrun
3939 // Convert libraries with no JVM_OnLoad, but which have Agent_OnLoad to be
3940 // treated like -agentpath:
3941 // Must be called before agent libraries are created
3942 void Threads::convert_vm_init_libraries_to_agents() {
3943 AgentLibrary* agent;
3944 AgentLibrary* next;
3945
3946 for (agent = Arguments::libraries(); agent != NULL; agent = next) {
3947 next = agent->next(); // cache the next agent now as this agent may get moved off this list
3948 OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
3949
3950 // If there is an JVM_OnLoad function it will get called later,
3951 // otherwise see if there is an Agent_OnLoad
3952 if (on_load_entry == NULL) {
3953 on_load_entry = lookup_agent_on_load(agent);
3954 if (on_load_entry != NULL) {
3955 // switch it to the agent list -- so that Agent_OnLoad will be called,
3956 // JVM_OnLoad won't be attempted and Agent_OnUnload will
3957 Arguments::convert_library_to_agent(agent);
3958 } else {
3959 vm_exit_during_initialization("Could not find JVM_OnLoad or Agent_OnLoad function in the library", agent->name());
3960 }
3961 }
3962 }
3963 }
3964
3965 // Create agents for -agentlib: -agentpath: and converted -Xrun
3966 // Invokes Agent_OnLoad
3967 // Called very early -- before JavaThreads exist
3968 void Threads::create_vm_init_agents() {
3969 extern struct JavaVM_ main_vm;
3970 AgentLibrary* agent;
3971
3972 JvmtiExport::enter_onload_phase();
3973
3974 for (agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
3975 OnLoadEntry_t on_load_entry = lookup_agent_on_load(agent);
3976
3977 if (on_load_entry != NULL) {
3978 // Invoke the Agent_OnLoad function
3979 jint err = (*on_load_entry)(&main_vm, agent->options(), NULL);
3980 if (err != JNI_OK) {
3981 vm_exit_during_initialization("agent library failed to init", agent->name());
3982 }
3983 } else {
3984 vm_exit_during_initialization("Could not find Agent_OnLoad function in the agent library", agent->name());
3985 }
3986 }
3987 JvmtiExport::enter_primordial_phase();
3988 }
3989
3990 extern "C" {
3991 typedef void (JNICALL *Agent_OnUnload_t)(JavaVM *);
3992 }
3993
3994 void Threads::shutdown_vm_agents() {
3995 // Send any Agent_OnUnload notifications
3996 const char *on_unload_symbols[] = AGENT_ONUNLOAD_SYMBOLS;
3997 size_t num_symbol_entries = ARRAY_SIZE(on_unload_symbols);
3998 extern struct JavaVM_ main_vm;
3999 for (AgentLibrary* agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
4000
4001 // Find the Agent_OnUnload function.
4002 Agent_OnUnload_t unload_entry = CAST_TO_FN_PTR(Agent_OnUnload_t,
4003 os::find_agent_function(agent,
4004 false,
4005 on_unload_symbols,
4006 num_symbol_entries));
4007
4008 // Invoke the Agent_OnUnload function
4009 if (unload_entry != NULL) {
4010 JavaThread* thread = JavaThread::current();
4011 ThreadToNativeFromVM ttn(thread);
4012 HandleMark hm(thread);
4013 (*unload_entry)(&main_vm);
4014 }
4015 }
4016 }
4017
4018 // Called for after the VM is initialized for -Xrun libraries which have not been converted to agent libraries
4019 // Invokes JVM_OnLoad
4020 void Threads::create_vm_init_libraries() {
4021 extern struct JavaVM_ main_vm;
4022 AgentLibrary* agent;
4023
4024 for (agent = Arguments::libraries(); agent != NULL; agent = agent->next()) {
4025 OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
4026
4027 if (on_load_entry != NULL) {
4028 // Invoke the JVM_OnLoad function
4029 JavaThread* thread = JavaThread::current();
4030 ThreadToNativeFromVM ttn(thread);
4031 HandleMark hm(thread);
4032 jint err = (*on_load_entry)(&main_vm, agent->options(), NULL);
4033 if (err != JNI_OK) {
4034 vm_exit_during_initialization("-Xrun library failed to init", agent->name());
4035 }
4036 } else {
4037 vm_exit_during_initialization("Could not find JVM_OnLoad function in -Xrun library", agent->name());
4038 }
4039 }
4040 }
4041
4042 JavaThread* Threads::find_java_thread_from_java_tid(jlong java_tid) {
4043 assert(Threads_lock->owned_by_self(), "Must hold Threads_lock");
4044
4045 JavaThread* java_thread = NULL;
4046 // Sequential search for now. Need to do better optimization later.
4047 for (JavaThread* thread = Threads::first(); thread != NULL; thread = thread->next()) {
4048 oop tobj = thread->threadObj();
4049 if (!thread->is_exiting() &&
4050 tobj != NULL &&
4051 java_tid == java_lang_Thread::thread_id(tobj)) {
4052 java_thread = thread;
4053 break;
4054 }
4055 }
4056 return java_thread;
4057 }
4058
4059
4060 // Last thread running calls java.lang.Shutdown.shutdown()
4061 void JavaThread::invoke_shutdown_hooks() {
4062 HandleMark hm(this);
4063
4064 // We could get here with a pending exception, if so clear it now.
4065 if (this->has_pending_exception()) {
4066 this->clear_pending_exception();
4067 }
4068
4069 EXCEPTION_MARK;
4070 Klass* shutdown_klass =
4071 SystemDictionary::resolve_or_null(vmSymbols::java_lang_Shutdown(),
4072 THREAD);
4073 if (shutdown_klass != NULL) {
4074 // SystemDictionary::resolve_or_null will return null if there was
4075 // an exception. If we cannot load the Shutdown class, just don't
4076 // call Shutdown.shutdown() at all. This will mean the shutdown hooks
4077 // and finalizers (if runFinalizersOnExit is set) won't be run.
4078 // Note that if a shutdown hook was registered or runFinalizersOnExit
4079 // was called, the Shutdown class would have already been loaded
4080 // (Runtime.addShutdownHook and runFinalizersOnExit will load it).
4081 JavaValue result(T_VOID);
4082 JavaCalls::call_static(&result,
4083 shutdown_klass,
4084 vmSymbols::shutdown_method_name(),
4085 vmSymbols::void_method_signature(),
4086 THREAD);
4087 }
4088 CLEAR_PENDING_EXCEPTION;
4089 }
4090
4091 // Threads::destroy_vm() is normally called from jni_DestroyJavaVM() when
4092 // the program falls off the end of main(). Another VM exit path is through
4093 // vm_exit() when the program calls System.exit() to return a value or when
4094 // there is a serious error in VM. The two shutdown paths are not exactly
4095 // the same, but they share Shutdown.shutdown() at Java level and before_exit()
4096 // and VM_Exit op at VM level.
4097 //
4098 // Shutdown sequence:
4099 // + Shutdown native memory tracking if it is on
4100 // + Wait until we are the last non-daemon thread to execute
4101 // <-- every thing is still working at this moment -->
4102 // + Call java.lang.Shutdown.shutdown(), which will invoke Java level
4103 // shutdown hooks, run finalizers if finalization-on-exit
4104 // + Call before_exit(), prepare for VM exit
4105 // > run VM level shutdown hooks (they are registered through JVM_OnExit(),
4106 // currently the only user of this mechanism is File.deleteOnExit())
4107 // > stop flat profiler, StatSampler, watcher thread, CMS threads,
4108 // post thread end and vm death events to JVMTI,
4109 // stop signal thread
4110 // + Call JavaThread::exit(), it will:
4111 // > release JNI handle blocks, remove stack guard pages
4112 // > remove this thread from Threads list
4113 // <-- no more Java code from this thread after this point -->
4114 // + Stop VM thread, it will bring the remaining VM to a safepoint and stop
4115 // the compiler threads at safepoint
4116 // <-- do not use anything that could get blocked by Safepoint -->
4117 // + Disable tracing at JNI/JVM barriers
4118 // + Set _vm_exited flag for threads that are still running native code
4119 // + Delete this thread
4120 // + Call exit_globals()
4121 // > deletes tty
4122 // > deletes PerfMemory resources
4123 // + Return to caller
4124
4125 bool Threads::destroy_vm() {
4126 JavaThread* thread = JavaThread::current();
4127
4128 #ifdef ASSERT
4129 _vm_complete = false;
4130 #endif
4131 // Wait until we are the last non-daemon thread to execute
4132 { MutexLocker nu(Threads_lock);
4133 while (Threads::number_of_non_daemon_threads() > 1)
4134 // This wait should make safepoint checks, wait without a timeout,
4135 // and wait as a suspend-equivalent condition.
4136 //
4137 // Note: If the FlatProfiler is running and this thread is waiting
4138 // for another non-daemon thread to finish, then the FlatProfiler
4139 // is waiting for the external suspend request on this thread to
4140 // complete. wait_for_ext_suspend_completion() will eventually
4141 // timeout, but that takes time. Making this wait a suspend-
4142 // equivalent condition solves that timeout problem.
4143 //
4144 Threads_lock->wait(!Mutex::_no_safepoint_check_flag, 0,
4145 Mutex::_as_suspend_equivalent_flag);
4146 }
4147
4148 // Hang forever on exit if we are reporting an error.
4149 if (ShowMessageBoxOnError && is_error_reported()) {
4150 os::infinite_sleep();
4151 }
4152 os::wait_for_keypress_at_exit();
4153
4154 // run Java level shutdown hooks
4155 thread->invoke_shutdown_hooks();
4156
4157 before_exit(thread);
4158
4159 thread->exit(true);
4160
4161 // Stop VM thread.
4162 {
4163 // 4945125 The vm thread comes to a safepoint during exit.
4164 // GC vm_operations can get caught at the safepoint, and the
4165 // heap is unparseable if they are caught. Grab the Heap_lock
4166 // to prevent this. The GC vm_operations will not be able to
4167 // queue until after the vm thread is dead. After this point,
4168 // we'll never emerge out of the safepoint before the VM exits.
4169
4170 MutexLocker ml(Heap_lock);
4171
4172 VMThread::wait_for_vm_thread_exit();
4173 assert(SafepointSynchronize::is_at_safepoint(), "VM thread should exit at Safepoint");
4174 VMThread::destroy();
4175 }
4176
4177 // clean up ideal graph printers
4178 #if defined(COMPILER2) && !defined(PRODUCT)
4179 IdealGraphPrinter::clean_up();
4180 #endif
4181
4182 // Now, all Java threads are gone except daemon threads. Daemon threads
4183 // running Java code or in VM are stopped by the Safepoint. However,
4184 // daemon threads executing native code are still running. But they
4185 // will be stopped at native=>Java/VM barriers. Note that we can't
4186 // simply kill or suspend them, as it is inherently deadlock-prone.
4187
4188 VM_Exit::set_vm_exited();
4189
4190 notify_vm_shutdown();
4191
4192 delete thread;
4193
4194 #if INCLUDE_JVMCI
4195 if (JVMCICounterSize > 0) {
4196 FREE_C_HEAP_ARRAY(jlong, JavaThread::_jvmci_old_thread_counters);
4197 }
4198 #endif
4199
4200 // exit_globals() will delete tty
4201 exit_globals();
4202
4203 LogConfiguration::finalize();
4204
4205 return true;
4206 }
4207
4208
4209 jboolean Threads::is_supported_jni_version_including_1_1(jint version) {
4210 if (version == JNI_VERSION_1_1) return JNI_TRUE;
4211 return is_supported_jni_version(version);
4212 }
4213
4214
4215 jboolean Threads::is_supported_jni_version(jint version) {
4216 if (version == JNI_VERSION_1_2) return JNI_TRUE;
4217 if (version == JNI_VERSION_1_4) return JNI_TRUE;
4218 if (version == JNI_VERSION_1_6) return JNI_TRUE;
4219 if (version == JNI_VERSION_1_8) return JNI_TRUE;
4220 if (version == JNI_VERSION_9) return JNI_TRUE;
4221 return JNI_FALSE;
4222 }
4223
4224
4225 void Threads::add(JavaThread* p, bool force_daemon) {
4226 // The threads lock must be owned at this point
4227 assert_locked_or_safepoint(Threads_lock);
4228
4229 // See the comment for this method in thread.hpp for its purpose and
4230 // why it is called here.
4231 p->initialize_queues();
4232 p->set_next(_thread_list);
4233 _thread_list = p;
4234 _number_of_threads++;
4235 oop threadObj = p->threadObj();
4236 bool daemon = true;
4237 // Bootstrapping problem: threadObj can be null for initial
4238 // JavaThread (or for threads attached via JNI)
4239 if ((!force_daemon) && (threadObj == NULL || !java_lang_Thread::is_daemon(threadObj))) {
4240 _number_of_non_daemon_threads++;
4241 daemon = false;
4242 }
4243
4244 ThreadService::add_thread(p, daemon);
4245
4246 // Possible GC point.
4247 Events::log(p, "Thread added: " INTPTR_FORMAT, p2i(p));
4248 }
4249
4250 void Threads::remove(JavaThread* p) {
4251
4252 // Reclaim the objectmonitors from the omFreeList of the moribund thread.
4253 ObjectSynchronizer::omFlush(p);
4254
4255 // Extra scope needed for Thread_lock, so we can check
4256 // that we do not remove thread without safepoint code notice
4257 { MutexLocker ml(Threads_lock);
4258
4259 assert(includes(p), "p must be present");
4260
4261 JavaThread* current = _thread_list;
4262 JavaThread* prev = NULL;
4263
4264 while (current != p) {
4265 prev = current;
4266 current = current->next();
4267 }
4268
4269 if (prev) {
4270 prev->set_next(current->next());
4271 } else {
4272 _thread_list = p->next();
4273 }
4274 _number_of_threads--;
4275 oop threadObj = p->threadObj();
4276 bool daemon = true;
4277 if (threadObj == NULL || !java_lang_Thread::is_daemon(threadObj)) {
4278 _number_of_non_daemon_threads--;
4279 daemon = false;
4280
4281 // Only one thread left, do a notify on the Threads_lock so a thread waiting
4282 // on destroy_vm will wake up.
4283 if (number_of_non_daemon_threads() == 1) {
4284 Threads_lock->notify_all();
4285 }
4286 }
4287 ThreadService::remove_thread(p, daemon);
4288
4289 // Make sure that safepoint code disregard this thread. This is needed since
4290 // the thread might mess around with locks after this point. This can cause it
4291 // to do callbacks into the safepoint code. However, the safepoint code is not aware
4292 // of this thread since it is removed from the queue.
4293 p->set_terminated_value();
4294 } // unlock Threads_lock
4295
4296 // Since Events::log uses a lock, we grab it outside the Threads_lock
4297 Events::log(p, "Thread exited: " INTPTR_FORMAT, p2i(p));
4298 }
4299
4300 // Threads_lock must be held when this is called (or must be called during a safepoint)
4301 bool Threads::includes(JavaThread* p) {
4302 assert(Threads_lock->is_locked(), "sanity check");
4303 ALL_JAVA_THREADS(q) {
4304 if (q == p) {
4305 return true;
4306 }
4307 }
4308 return false;
4309 }
4310
4311 // Operations on the Threads list for GC. These are not explicitly locked,
4312 // but the garbage collector must provide a safe context for them to run.
4313 // In particular, these things should never be called when the Threads_lock
4314 // is held by some other thread. (Note: the Safepoint abstraction also
4315 // uses the Threads_lock to guarantee this property. It also makes sure that
4316 // all threads gets blocked when exiting or starting).
4317
4318 void Threads::oops_do(OopClosure* f, CodeBlobClosure* cf) {
4319 ALL_JAVA_THREADS(p) {
4320 p->oops_do(f, cf);
4321 }
4322 VMThread::vm_thread()->oops_do(f, cf);
4323 }
4324
4325 void Threads::change_thread_claim_parity() {
4326 // Set the new claim parity.
4327 assert(_thread_claim_parity >= 0 && _thread_claim_parity <= 2,
4328 "Not in range.");
4329 _thread_claim_parity++;
4330 if (_thread_claim_parity == 3) _thread_claim_parity = 1;
4331 assert(_thread_claim_parity >= 1 && _thread_claim_parity <= 2,
4332 "Not in range.");
4333 }
4334
4335 #ifdef ASSERT
4336 void Threads::assert_all_threads_claimed() {
4337 ALL_JAVA_THREADS(p) {
4338 const int thread_parity = p->oops_do_parity();
4339 assert((thread_parity == _thread_claim_parity),
4340 "Thread " PTR_FORMAT " has incorrect parity %d != %d", p2i(p), thread_parity, _thread_claim_parity);
4341 }
4342 }
4343 #endif // ASSERT
4344
4345 void Threads::possibly_parallel_oops_do(bool is_par, OopClosure* f, CodeBlobClosure* cf) {
4346 int cp = Threads::thread_claim_parity();
4347 ALL_JAVA_THREADS(p) {
4348 if (p->claim_oops_do(is_par, cp)) {
4349 p->oops_do(f, cf);
4350 }
4351 }
4352 VMThread* vmt = VMThread::vm_thread();
4353 if (vmt->claim_oops_do(is_par, cp)) {
4354 vmt->oops_do(f, cf);
4355 }
4356 }
4357
4358 #if INCLUDE_ALL_GCS
4359 // Used by ParallelScavenge
4360 void Threads::create_thread_roots_tasks(GCTaskQueue* q) {
4361 ALL_JAVA_THREADS(p) {
4362 q->enqueue(new ThreadRootsTask(p));
4363 }
4364 q->enqueue(new ThreadRootsTask(VMThread::vm_thread()));
4365 }
4366
4367 // Used by Parallel Old
4368 void Threads::create_thread_roots_marking_tasks(GCTaskQueue* q) {
4369 ALL_JAVA_THREADS(p) {
4370 q->enqueue(new ThreadRootsMarkingTask(p));
4371 }
4372 q->enqueue(new ThreadRootsMarkingTask(VMThread::vm_thread()));
4373 }
4374 #endif // INCLUDE_ALL_GCS
4375
4376 void Threads::nmethods_do(CodeBlobClosure* cf) {
4377 ALL_JAVA_THREADS(p) {
4378 // This is used by the code cache sweeper to mark nmethods that are active
4379 // on the stack of a Java thread. Ignore the sweeper thread itself to avoid
4380 // marking CodeCacheSweeperThread::_scanned_compiled_method as active.
4381 if(!p->is_Code_cache_sweeper_thread()) {
4382 p->nmethods_do(cf);
4383 }
4384 }
4385 }
4386
4387 void Threads::metadata_do(void f(Metadata*)) {
4388 ALL_JAVA_THREADS(p) {
4389 p->metadata_do(f);
4390 }
4391 }
4392
4393 class ThreadHandlesClosure : public ThreadClosure {
4394 void (*_f)(Metadata*);
4395 public:
4396 ThreadHandlesClosure(void f(Metadata*)) : _f(f) {}
4397 virtual void do_thread(Thread* thread) {
4398 thread->metadata_handles_do(_f);
4399 }
4400 };
4401
4402 void Threads::metadata_handles_do(void f(Metadata*)) {
4403 // Only walk the Handles in Thread.
4404 ThreadHandlesClosure handles_closure(f);
4405 threads_do(&handles_closure);
4406 }
4407
4408 void Threads::deoptimized_wrt_marked_nmethods() {
4409 ALL_JAVA_THREADS(p) {
4410 p->deoptimized_wrt_marked_nmethods();
4411 }
4412 }
4413
4414
4415 // Get count Java threads that are waiting to enter the specified monitor.
4416 GrowableArray<JavaThread*>* Threads::get_pending_threads(int count,
4417 address monitor,
4418 bool doLock) {
4419 assert(doLock || SafepointSynchronize::is_at_safepoint(),
4420 "must grab Threads_lock or be at safepoint");
4421 GrowableArray<JavaThread*>* result = new GrowableArray<JavaThread*>(count);
4422
4423 int i = 0;
4424 {
4425 MutexLockerEx ml(doLock ? Threads_lock : NULL);
4426 ALL_JAVA_THREADS(p) {
4427 if (!p->can_call_java()) continue;
4428
4429 address pending = (address)p->current_pending_monitor();
4430 if (pending == monitor) { // found a match
4431 if (i < count) result->append(p); // save the first count matches
4432 i++;
4433 }
4434 }
4435 }
4436 return result;
4437 }
4438
4439
4440 JavaThread *Threads::owning_thread_from_monitor_owner(address owner,
4441 bool doLock) {
4442 assert(doLock ||
4443 Threads_lock->owned_by_self() ||
4444 SafepointSynchronize::is_at_safepoint(),
4445 "must grab Threads_lock or be at safepoint");
4446
4447 // NULL owner means not locked so we can skip the search
4448 if (owner == NULL) return NULL;
4449
4450 {
4451 MutexLockerEx ml(doLock ? Threads_lock : NULL);
4452 ALL_JAVA_THREADS(p) {
4453 // first, see if owner is the address of a Java thread
4454 if (owner == (address)p) return p;
4455 }
4456 }
4457 // Cannot assert on lack of success here since this function may be
4458 // used by code that is trying to report useful problem information
4459 // like deadlock detection.
4460 if (UseHeavyMonitors) return NULL;
4461
4462 // If we didn't find a matching Java thread and we didn't force use of
4463 // heavyweight monitors, then the owner is the stack address of the
4464 // Lock Word in the owning Java thread's stack.
4465 //
4466 JavaThread* the_owner = NULL;
4467 {
4468 MutexLockerEx ml(doLock ? Threads_lock : NULL);
4469 ALL_JAVA_THREADS(q) {
4470 if (q->is_lock_owned(owner)) {
4471 the_owner = q;
4472 break;
4473 }
4474 }
4475 }
4476 // cannot assert on lack of success here; see above comment
4477 return the_owner;
4478 }
4479
4480 // Threads::print_on() is called at safepoint by VM_PrintThreads operation.
4481 void Threads::print_on(outputStream* st, bool print_stacks,
4482 bool internal_format, bool print_concurrent_locks) {
4483 char buf[32];
4484 st->print_raw_cr(os::local_time_string(buf, sizeof(buf)));
4485
4486 st->print_cr("Full thread dump %s (%s %s):",
4487 Abstract_VM_Version::vm_name(),
4488 Abstract_VM_Version::vm_release(),
4489 Abstract_VM_Version::vm_info_string());
4490 st->cr();
4491
4492 #if INCLUDE_SERVICES
4493 // Dump concurrent locks
4494 ConcurrentLocksDump concurrent_locks;
4495 if (print_concurrent_locks) {
4496 concurrent_locks.dump_at_safepoint();
4497 }
4498 #endif // INCLUDE_SERVICES
4499
4500 ALL_JAVA_THREADS(p) {
4501 ResourceMark rm;
4502 p->print_on(st);
4503 if (print_stacks) {
4504 if (internal_format) {
4505 p->trace_stack();
4506 } else {
4507 p->print_stack_on(st);
4508 }
4509 }
4510 st->cr();
4511 #if INCLUDE_SERVICES
4512 if (print_concurrent_locks) {
4513 concurrent_locks.print_locks_on(p, st);
4514 }
4515 #endif // INCLUDE_SERVICES
4516 }
4517
4518 VMThread::vm_thread()->print_on(st);
4519 st->cr();
4520 Universe::heap()->print_gc_threads_on(st);
4521 WatcherThread* wt = WatcherThread::watcher_thread();
4522 if (wt != NULL) {
4523 wt->print_on(st);
4524 st->cr();
4525 }
4526 st->flush();
4527 }
4528
4529 void Threads::print_on_error(Thread* this_thread, outputStream* st, Thread* current, char* buf,
4530 int buflen, bool* found_current) {
4531 if (this_thread != NULL) {
4532 bool is_current = (current == this_thread);
4533 *found_current = *found_current || is_current;
4534 st->print("%s", is_current ? "=>" : " ");
4535
4536 st->print(PTR_FORMAT, p2i(this_thread));
4537 st->print(" ");
4538 this_thread->print_on_error(st, buf, buflen);
4539 st->cr();
4540 }
4541 }
4542
4543 class PrintOnErrorClosure : public ThreadClosure {
4544 outputStream* _st;
4545 Thread* _current;
4546 char* _buf;
4547 int _buflen;
4548 bool* _found_current;
4549 public:
4550 PrintOnErrorClosure(outputStream* st, Thread* current, char* buf,
4551 int buflen, bool* found_current) :
4552 _st(st), _current(current), _buf(buf), _buflen(buflen), _found_current(found_current) {}
4553
4554 virtual void do_thread(Thread* thread) {
4555 Threads::print_on_error(thread, _st, _current, _buf, _buflen, _found_current);
4556 }
4557 };
4558
4559 // Threads::print_on_error() is called by fatal error handler. It's possible
4560 // that VM is not at safepoint and/or current thread is inside signal handler.
4561 // Don't print stack trace, as the stack may not be walkable. Don't allocate
4562 // memory (even in resource area), it might deadlock the error handler.
4563 void Threads::print_on_error(outputStream* st, Thread* current, char* buf,
4564 int buflen) {
4565 bool found_current = false;
4566 st->print_cr("Java Threads: ( => current thread )");
4567 ALL_JAVA_THREADS(thread) {
4568 print_on_error(thread, st, current, buf, buflen, &found_current);
4569 }
4570 st->cr();
4571
4572 st->print_cr("Other Threads:");
4573 print_on_error(VMThread::vm_thread(), st, current, buf, buflen, &found_current);
4574 print_on_error(WatcherThread::watcher_thread(), st, current, buf, buflen, &found_current);
4575
4576 PrintOnErrorClosure print_closure(st, current, buf, buflen, &found_current);
4577 Universe::heap()->gc_threads_do(&print_closure);
4578
4579 if (!found_current) {
4580 st->cr();
4581 st->print("=>" PTR_FORMAT " (exited) ", p2i(current));
4582 current->print_on_error(st, buf, buflen);
4583 st->cr();
4584 }
4585 st->cr();
4586 st->print_cr("Threads with active compile tasks:");
4587 print_threads_compiling(st, buf, buflen);
4588 }
4589
4590 void Threads::print_threads_compiling(outputStream* st, char* buf, int buflen) {
4591 ALL_JAVA_THREADS(thread) {
4592 if (thread->is_Compiler_thread()) {
4593 CompilerThread* ct = (CompilerThread*) thread;
4594 if (ct->task() != NULL) {
4595 thread->print_name_on_error(st, buf, buflen);
4596 ct->task()->print(st, NULL, true, true);
4597 }
4598 }
4599 }
4600 }
4601
4602
4603 // Internal SpinLock and Mutex
4604 // Based on ParkEvent
4605
4606 // Ad-hoc mutual exclusion primitives: SpinLock and Mux
4607 //
4608 // We employ SpinLocks _only for low-contention, fixed-length
4609 // short-duration critical sections where we're concerned
4610 // about native mutex_t or HotSpot Mutex:: latency.
4611 // The mux construct provides a spin-then-block mutual exclusion
4612 // mechanism.
4613 //
4614 // Testing has shown that contention on the ListLock guarding gFreeList
4615 // is common. If we implement ListLock as a simple SpinLock it's common
4616 // for the JVM to devolve to yielding with little progress. This is true
4617 // despite the fact that the critical sections protected by ListLock are
4618 // extremely short.
4619 //
4620 // TODO-FIXME: ListLock should be of type SpinLock.
4621 // We should make this a 1st-class type, integrated into the lock
4622 // hierarchy as leaf-locks. Critically, the SpinLock structure
4623 // should have sufficient padding to avoid false-sharing and excessive
4624 // cache-coherency traffic.
4625
4626
4627 typedef volatile int SpinLockT;
4628
4629 void Thread::SpinAcquire(volatile int * adr, const char * LockName) {
4630 if (Atomic::cmpxchg (1, adr, 0) == 0) {
4631 return; // normal fast-path return
4632 }
4633
4634 // Slow-path : We've encountered contention -- Spin/Yield/Block strategy.
4635 TEVENT(SpinAcquire - ctx);
4636 int ctr = 0;
4637 int Yields = 0;
4638 for (;;) {
4639 while (*adr != 0) {
4640 ++ctr;
4641 if ((ctr & 0xFFF) == 0 || !os::is_MP()) {
4642 if (Yields > 5) {
4643 os::naked_short_sleep(1);
4644 } else {
4645 os::naked_yield();
4646 ++Yields;
4647 }
4648 } else {
4649 SpinPause();
4650 }
4651 }
4652 if (Atomic::cmpxchg(1, adr, 0) == 0) return;
4653 }
4654 }
4655
4656 void Thread::SpinRelease(volatile int * adr) {
4657 assert(*adr != 0, "invariant");
4658 OrderAccess::fence(); // guarantee at least release consistency.
4659 // Roach-motel semantics.
4660 // It's safe if subsequent LDs and STs float "up" into the critical section,
4661 // but prior LDs and STs within the critical section can't be allowed
4662 // to reorder or float past the ST that releases the lock.
4663 // Loads and stores in the critical section - which appear in program
4664 // order before the store that releases the lock - must also appear
4665 // before the store that releases the lock in memory visibility order.
4666 // Conceptually we need a #loadstore|#storestore "release" MEMBAR before
4667 // the ST of 0 into the lock-word which releases the lock, so fence
4668 // more than covers this on all platforms.
4669 *adr = 0;
4670 }
4671
4672 // muxAcquire and muxRelease:
4673 //
4674 // * muxAcquire and muxRelease support a single-word lock-word construct.
4675 // The LSB of the word is set IFF the lock is held.
4676 // The remainder of the word points to the head of a singly-linked list
4677 // of threads blocked on the lock.
4678 //
4679 // * The current implementation of muxAcquire-muxRelease uses its own
4680 // dedicated Thread._MuxEvent instance. If we're interested in
4681 // minimizing the peak number of extant ParkEvent instances then
4682 // we could eliminate _MuxEvent and "borrow" _ParkEvent as long
4683 // as certain invariants were satisfied. Specifically, care would need
4684 // to be taken with regards to consuming unpark() "permits".
4685 // A safe rule of thumb is that a thread would never call muxAcquire()
4686 // if it's enqueued (cxq, EntryList, WaitList, etc) and will subsequently
4687 // park(). Otherwise the _ParkEvent park() operation in muxAcquire() could
4688 // consume an unpark() permit intended for monitorenter, for instance.
4689 // One way around this would be to widen the restricted-range semaphore
4690 // implemented in park(). Another alternative would be to provide
4691 // multiple instances of the PlatformEvent() for each thread. One
4692 // instance would be dedicated to muxAcquire-muxRelease, for instance.
4693 //
4694 // * Usage:
4695 // -- Only as leaf locks
4696 // -- for short-term locking only as muxAcquire does not perform
4697 // thread state transitions.
4698 //
4699 // Alternatives:
4700 // * We could implement muxAcquire and muxRelease with MCS or CLH locks
4701 // but with parking or spin-then-park instead of pure spinning.
4702 // * Use Taura-Oyama-Yonenzawa locks.
4703 // * It's possible to construct a 1-0 lock if we encode the lockword as
4704 // (List,LockByte). Acquire will CAS the full lockword while Release
4705 // will STB 0 into the LockByte. The 1-0 scheme admits stranding, so
4706 // acquiring threads use timers (ParkTimed) to detect and recover from
4707 // the stranding window. Thread/Node structures must be aligned on 256-byte
4708 // boundaries by using placement-new.
4709 // * Augment MCS with advisory back-link fields maintained with CAS().
4710 // Pictorially: LockWord -> T1 <-> T2 <-> T3 <-> ... <-> Tn <-> Owner.
4711 // The validity of the backlinks must be ratified before we trust the value.
4712 // If the backlinks are invalid the exiting thread must back-track through the
4713 // the forward links, which are always trustworthy.
4714 // * Add a successor indication. The LockWord is currently encoded as
4715 // (List, LOCKBIT:1). We could also add a SUCCBIT or an explicit _succ variable
4716 // to provide the usual futile-wakeup optimization.
4717 // See RTStt for details.
4718 // * Consider schedctl.sc_nopreempt to cover the critical section.
4719 //
4720
4721
4722 typedef volatile intptr_t MutexT; // Mux Lock-word
4723 enum MuxBits { LOCKBIT = 1 };
4724
4725 void Thread::muxAcquire(volatile intptr_t * Lock, const char * LockName) {
4726 intptr_t w = Atomic::cmpxchg_ptr(LOCKBIT, Lock, 0);
4727 if (w == 0) return;
4728 if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4729 return;
4730 }
4731
4732 TEVENT(muxAcquire - Contention);
4733 ParkEvent * const Self = Thread::current()->_MuxEvent;
4734 assert((intptr_t(Self) & LOCKBIT) == 0, "invariant");
4735 for (;;) {
4736 int its = (os::is_MP() ? 100 : 0) + 1;
4737
4738 // Optional spin phase: spin-then-park strategy
4739 while (--its >= 0) {
4740 w = *Lock;
4741 if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4742 return;
4743 }
4744 }
4745
4746 Self->reset();
4747 Self->OnList = intptr_t(Lock);
4748 // The following fence() isn't _strictly necessary as the subsequent
4749 // CAS() both serializes execution and ratifies the fetched *Lock value.
4750 OrderAccess::fence();
4751 for (;;) {
4752 w = *Lock;
4753 if ((w & LOCKBIT) == 0) {
4754 if (Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4755 Self->OnList = 0; // hygiene - allows stronger asserts
4756 return;
4757 }
4758 continue; // Interference -- *Lock changed -- Just retry
4759 }
4760 assert(w & LOCKBIT, "invariant");
4761 Self->ListNext = (ParkEvent *) (w & ~LOCKBIT);
4762 if (Atomic::cmpxchg_ptr(intptr_t(Self)|LOCKBIT, Lock, w) == w) break;
4763 }
4764
4765 while (Self->OnList != 0) {
4766 Self->park();
4767 }
4768 }
4769 }
4770
4771 void Thread::muxAcquireW(volatile intptr_t * Lock, ParkEvent * ev) {
4772 intptr_t w = Atomic::cmpxchg_ptr(LOCKBIT, Lock, 0);
4773 if (w == 0) return;
4774 if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4775 return;
4776 }
4777
4778 TEVENT(muxAcquire - Contention);
4779 ParkEvent * ReleaseAfter = NULL;
4780 if (ev == NULL) {
4781 ev = ReleaseAfter = ParkEvent::Allocate(NULL);
4782 }
4783 assert((intptr_t(ev) & LOCKBIT) == 0, "invariant");
4784 for (;;) {
4785 guarantee(ev->OnList == 0, "invariant");
4786 int its = (os::is_MP() ? 100 : 0) + 1;
4787
4788 // Optional spin phase: spin-then-park strategy
4789 while (--its >= 0) {
4790 w = *Lock;
4791 if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4792 if (ReleaseAfter != NULL) {
4793 ParkEvent::Release(ReleaseAfter);
4794 }
4795 return;
4796 }
4797 }
4798
4799 ev->reset();
4800 ev->OnList = intptr_t(Lock);
4801 // The following fence() isn't _strictly necessary as the subsequent
4802 // CAS() both serializes execution and ratifies the fetched *Lock value.
4803 OrderAccess::fence();
4804 for (;;) {
4805 w = *Lock;
4806 if ((w & LOCKBIT) == 0) {
4807 if (Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4808 ev->OnList = 0;
4809 // We call ::Release while holding the outer lock, thus
4810 // artificially lengthening the critical section.
4811 // Consider deferring the ::Release() until the subsequent unlock(),
4812 // after we've dropped the outer lock.
4813 if (ReleaseAfter != NULL) {
4814 ParkEvent::Release(ReleaseAfter);
4815 }
4816 return;
4817 }
4818 continue; // Interference -- *Lock changed -- Just retry
4819 }
4820 assert(w & LOCKBIT, "invariant");
4821 ev->ListNext = (ParkEvent *) (w & ~LOCKBIT);
4822 if (Atomic::cmpxchg_ptr(intptr_t(ev)|LOCKBIT, Lock, w) == w) break;
4823 }
4824
4825 while (ev->OnList != 0) {
4826 ev->park();
4827 }
4828 }
4829 }
4830
4831 // Release() must extract a successor from the list and then wake that thread.
4832 // It can "pop" the front of the list or use a detach-modify-reattach (DMR) scheme
4833 // similar to that used by ParkEvent::Allocate() and ::Release(). DMR-based
4834 // Release() would :
4835 // (A) CAS() or swap() null to *Lock, releasing the lock and detaching the list.
4836 // (B) Extract a successor from the private list "in-hand"
4837 // (C) attempt to CAS() the residual back into *Lock over null.
4838 // If there were any newly arrived threads and the CAS() would fail.
4839 // In that case Release() would detach the RATs, re-merge the list in-hand
4840 // with the RATs and repeat as needed. Alternately, Release() might
4841 // detach and extract a successor, but then pass the residual list to the wakee.
4842 // The wakee would be responsible for reattaching and remerging before it
4843 // competed for the lock.
4844 //
4845 // Both "pop" and DMR are immune from ABA corruption -- there can be
4846 // multiple concurrent pushers, but only one popper or detacher.
4847 // This implementation pops from the head of the list. This is unfair,
4848 // but tends to provide excellent throughput as hot threads remain hot.
4849 // (We wake recently run threads first).
4850 //
4851 // All paths through muxRelease() will execute a CAS.
4852 // Release consistency -- We depend on the CAS in muxRelease() to provide full
4853 // bidirectional fence/MEMBAR semantics, ensuring that all prior memory operations
4854 // executed within the critical section are complete and globally visible before the
4855 // store (CAS) to the lock-word that releases the lock becomes globally visible.
4856 void Thread::muxRelease(volatile intptr_t * Lock) {
4857 for (;;) {
4858 const intptr_t w = Atomic::cmpxchg_ptr(0, Lock, LOCKBIT);
4859 assert(w & LOCKBIT, "invariant");
4860 if (w == LOCKBIT) return;
4861 ParkEvent * const List = (ParkEvent *) (w & ~LOCKBIT);
4862 assert(List != NULL, "invariant");
4863 assert(List->OnList == intptr_t(Lock), "invariant");
4864 ParkEvent * const nxt = List->ListNext;
4865 guarantee((intptr_t(nxt) & LOCKBIT) == 0, "invariant");
4866
4867 // The following CAS() releases the lock and pops the head element.
4868 // The CAS() also ratifies the previously fetched lock-word value.
4869 if (Atomic::cmpxchg_ptr (intptr_t(nxt), Lock, w) != w) {
4870 continue;
4871 }
4872 List->OnList = 0;
4873 OrderAccess::fence();
4874 List->unpark();
4875 return;
4876 }
4877 }
4878
4879
4880 void Threads::verify() {
4881 ALL_JAVA_THREADS(p) {
4882 p->verify();
4883 }
4884 VMThread* thread = VMThread::vm_thread();
4885 if (thread != NULL) thread->verify();
4886 }