1 /*
2 * Copyright (c) 1997, 2014, 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/symbolTable.hpp"
27 #include "classfile/systemDictionary.hpp"
28 #include "code/codeCache.hpp"
29 #include "code/icBuffer.hpp"
30 #include "code/nmethod.hpp"
31 #include "code/pcDesc.hpp"
32 #include "code/scopeDesc.hpp"
33 #include "gc_interface/collectedHeap.hpp"
34 #include "interpreter/interpreter.hpp"
35 #include "memory/gcLocker.inline.hpp"
36 #include "memory/resourceArea.hpp"
37 #include "memory/universe.inline.hpp"
38 #include "oops/oop.inline.hpp"
39 #include "oops/symbol.hpp"
40 #include "runtime/atomic.inline.hpp"
41 #include "runtime/compilationPolicy.hpp"
42 #include "runtime/deoptimization.hpp"
43 #include "runtime/frame.inline.hpp"
44 #include "runtime/interfaceSupport.hpp"
45 #include "runtime/mutexLocker.hpp"
46 #include "runtime/orderAccess.inline.hpp"
47 #include "runtime/osThread.hpp"
48 #include "runtime/safepoint.hpp"
49 #include "runtime/signature.hpp"
50 #include "runtime/stubCodeGenerator.hpp"
51 #include "runtime/stubRoutines.hpp"
52 #include "runtime/sweeper.hpp"
53 #include "runtime/synchronizer.hpp"
54 #include "runtime/thread.inline.hpp"
55 #include "services/runtimeService.hpp"
56 #include "utilities/events.hpp"
57 #include "utilities/macros.hpp"
58 #ifdef TARGET_ARCH_x86
59 # include "nativeInst_x86.hpp"
60 # include "vmreg_x86.inline.hpp"
61 #endif
62 #ifdef TARGET_ARCH_sparc
63 # include "nativeInst_sparc.hpp"
64 # include "vmreg_sparc.inline.hpp"
65 #endif
66 #ifdef TARGET_ARCH_zero
67 # include "nativeInst_zero.hpp"
68 # include "vmreg_zero.inline.hpp"
69 #endif
70 #ifdef TARGET_ARCH_arm
71 # include "nativeInst_arm.hpp"
72 # include "vmreg_arm.inline.hpp"
73 #endif
74 #ifdef TARGET_ARCH_ppc
75 # include "nativeInst_ppc.hpp"
76 # include "vmreg_ppc.inline.hpp"
77 #endif
78 #if INCLUDE_ALL_GCS
79 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
80 #include "gc_implementation/shared/suspendibleThreadSet.hpp"
81 #endif // INCLUDE_ALL_GCS
82 #ifdef COMPILER1
83 #include "c1/c1_globals.hpp"
84 #endif
85
86 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
87
88 // --------------------------------------------------------------------------------------------------
89 // Implementation of Safepoint begin/end
90
91 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
92 volatile int SafepointSynchronize::_waiting_to_block = 0;
93 volatile int SafepointSynchronize::_safepoint_counter = 0;
94 int SafepointSynchronize::_current_jni_active_count = 0;
95 long SafepointSynchronize::_end_of_last_safepoint = 0;
96 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
97 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
98 static bool timeout_error_printed = false;
99
100 // Roll all threads forward to a safepoint and suspend them all
101 void SafepointSynchronize::begin() {
102
103 Thread* myThread = Thread::current();
104 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
105
106 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
107 _safepoint_begin_time = os::javaTimeNanos();
108 _ts_of_current_safepoint = tty->time_stamp().seconds();
109 }
110
111 #if INCLUDE_ALL_GCS
112 if (UseConcMarkSweepGC) {
113 // In the future we should investigate whether CMS can use the
114 // more-general mechanism below. DLD (01/05).
115 ConcurrentMarkSweepThread::synchronize(false);
116 } else if (UseG1GC) {
117 SuspendibleThreadSet::synchronize();
118 }
119 #endif // INCLUDE_ALL_GCS
120
121 // By getting the Threads_lock, we assure that no threads are about to start or
122 // exit. It is released again in SafepointSynchronize::end().
123 Threads_lock->lock();
124
125 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
126
127 int nof_threads = Threads::number_of_threads();
128
129 if (TraceSafepoint) {
130 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
131 }
132
133 RuntimeService::record_safepoint_begin();
134
135 MutexLocker mu(Safepoint_lock);
136
137 // Reset the count of active JNI critical threads
138 _current_jni_active_count = 0;
139
140 // Set number of threads to wait for, before we initiate the callbacks
141 _waiting_to_block = nof_threads;
142 TryingToBlock = 0 ;
143 int still_running = nof_threads;
144
145 // Save the starting time, so that it can be compared to see if this has taken
146 // too long to complete.
147 jlong safepoint_limit_time;
148 timeout_error_printed = false;
149
150 // PrintSafepointStatisticsTimeout can be specified separately. When
151 // specified, PrintSafepointStatistics will be set to true in
152 // deferred_initialize_stat method. The initialization has to be done
153 // early enough to avoid any races. See bug 6880029 for details.
154 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
155 deferred_initialize_stat();
156 }
157
158 // Begin the process of bringing the system to a safepoint.
159 // Java threads can be in several different states and are
160 // stopped by different mechanisms:
161 //
162 // 1. Running interpreted
163 // The interpeter dispatch table is changed to force it to
164 // check for a safepoint condition between bytecodes.
165 // 2. Running in native code
166 // When returning from the native code, a Java thread must check
167 // the safepoint _state to see if we must block. If the
168 // VM thread sees a Java thread in native, it does
169 // not wait for this thread to block. The order of the memory
170 // writes and reads of both the safepoint state and the Java
171 // threads state is critical. In order to guarantee that the
172 // memory writes are serialized with respect to each other,
173 // the VM thread issues a memory barrier instruction
174 // (on MP systems). In order to avoid the overhead of issuing
175 // a memory barrier for each Java thread making native calls, each Java
176 // thread performs a write to a single memory page after changing
177 // the thread state. The VM thread performs a sequence of
178 // mprotect OS calls which forces all previous writes from all
179 // Java threads to be serialized. This is done in the
180 // os::serialize_thread_states() call. This has proven to be
181 // much more efficient than executing a membar instruction
182 // on every call to native code.
183 // 3. Running compiled Code
184 // Compiled code reads a global (Safepoint Polling) page that
185 // is set to fault if we are trying to get to a safepoint.
186 // 4. Blocked
187 // A thread which is blocked will not be allowed to return from the
188 // block condition until the safepoint operation is complete.
189 // 5. In VM or Transitioning between states
190 // If a Java thread is currently running in the VM or transitioning
191 // between states, the safepointing code will wait for the thread to
192 // block itself when it attempts transitions to a new state.
193 //
194 _state = _synchronizing;
195 OrderAccess::fence();
196
197 // Flush all thread states to memory
198 if (!UseMembar) {
199 os::serialize_thread_states();
200 }
201
202 // Make interpreter safepoint aware
203 Interpreter::notice_safepoints();
204
205 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
206 // Make polling safepoint aware
207 guarantee (PageArmed == 0, "invariant") ;
208 PageArmed = 1 ;
209 os::make_polling_page_unreadable();
210 }
211
212 // Consider using active_processor_count() ... but that call is expensive.
213 int ncpus = os::processor_count() ;
214
215 #ifdef ASSERT
216 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
217 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
218 // Clear the visited flag to ensure that the critical counts are collected properly.
219 cur->set_visited_for_critical_count(false);
220 }
221 #endif // ASSERT
222
223 if (SafepointTimeout)
224 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
225
226 // Iterate through all threads until it have been determined how to stop them all at a safepoint
227 unsigned int iterations = 0;
228 int steps = 0 ;
229 while(still_running > 0) {
230 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
231 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
232 ThreadSafepointState *cur_state = cur->safepoint_state();
233 if (cur_state->is_running()) {
234 cur_state->examine_state_of_thread();
235 if (!cur_state->is_running()) {
236 still_running--;
237 // consider adjusting steps downward:
238 // steps = 0
239 // steps -= NNN
240 // steps >>= 1
241 // steps = MIN(steps, 2000-100)
242 // if (iterations != 0) steps -= NNN
243 }
244 if (TraceSafepoint && Verbose) cur_state->print();
245 }
246 }
247
248 if (PrintSafepointStatistics && iterations == 0) {
249 begin_statistics(nof_threads, still_running);
250 }
251
252 if (still_running > 0) {
253 // Check for if it takes to long
254 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
255 print_safepoint_timeout(_spinning_timeout);
256 }
257
258 // Spin to avoid context switching.
259 // There's a tension between allowing the mutators to run (and rendezvous)
260 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
261 // a mutator might otherwise use profitably to reach a safepoint. Excessive
262 // spinning by the VM thread on a saturated system can increase rendezvous latency.
263 // Blocking or yielding incur their own penalties in the form of context switching
264 // and the resultant loss of $ residency.
265 //
266 // Further complicating matters is that yield() does not work as naively expected
267 // on many platforms -- yield() does not guarantee that any other ready threads
268 // will run. As such we revert yield_all() after some number of iterations.
269 // Yield_all() is implemented as a short unconditional sleep on some platforms.
270 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
271 // can actually increase the time it takes the VM thread to detect that a system-wide
272 // stop-the-world safepoint has been reached. In a pathological scenario such as that
273 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
274 // In that case the mutators will be stalled waiting for the safepoint to complete and the
275 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
276 // will eventually wake up and detect that all mutators are safe, at which point
277 // we'll again make progress.
278 //
279 // Beware too that that the VMThread typically runs at elevated priority.
280 // Its default priority is higher than the default mutator priority.
281 // Obviously, this complicates spinning.
282 //
283 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
284 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
285 //
286 // See the comments in synchronizer.cpp for additional remarks on spinning.
287 //
288 // In the future we might:
289 // 1. Modify the safepoint scheme to avoid potentally unbounded spinning.
290 // This is tricky as the path used by a thread exiting the JVM (say on
291 // on JNI call-out) simply stores into its state field. The burden
292 // is placed on the VM thread, which must poll (spin).
293 // 2. Find something useful to do while spinning. If the safepoint is GC-related
294 // we might aggressively scan the stacks of threads that are already safe.
295 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
296 // If all the mutators are ONPROC there's no reason to sleep or yield.
297 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
298 // 5. Check system saturation. If the system is not fully saturated then
299 // simply spin and avoid sleep/yield.
300 // 6. As still-running mutators rendezvous they could unpark the sleeping
301 // VMthread. This works well for still-running mutators that become
302 // safe. The VMthread must still poll for mutators that call-out.
303 // 7. Drive the policy on time-since-begin instead of iterations.
304 // 8. Consider making the spin duration a function of the # of CPUs:
305 // Spin = (((ncpus-1) * M) + K) + F(still_running)
306 // Alternately, instead of counting iterations of the outer loop
307 // we could count the # of threads visited in the inner loop, above.
308 // 9. On windows consider using the return value from SwitchThreadTo()
309 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
310
311 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
312 guarantee (PageArmed == 0, "invariant") ;
313 PageArmed = 1 ;
314 os::make_polling_page_unreadable();
315 }
316
317 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
318 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
319 ++steps ;
320 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
321 SpinPause() ; // MP-Polite spin
322 } else
323 if (steps < DeferThrSuspendLoopCount) {
324 os::NakedYield() ;
325 } else {
326 os::yield_all(steps) ;
327 // Alternately, the VM thread could transiently depress its scheduling priority or
328 // transiently increase the priority of the tardy mutator(s).
329 }
330
331 iterations ++ ;
332 }
333 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
334 }
335 assert(still_running == 0, "sanity check");
336
337 if (PrintSafepointStatistics) {
338 update_statistics_on_spin_end();
339 }
340
341 // wait until all threads are stopped
342 while (_waiting_to_block > 0) {
343 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
344 if (!SafepointTimeout || timeout_error_printed) {
345 Safepoint_lock->wait(true); // true, means with no safepoint checks
346 } else {
347 // Compute remaining time
348 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
349
350 // If there is no remaining time, then there is an error
351 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
352 print_safepoint_timeout(_blocking_timeout);
353 }
354 }
355 }
356 assert(_waiting_to_block == 0, "sanity check");
357
358 #ifndef PRODUCT
359 if (SafepointTimeout) {
360 jlong current_time = os::javaTimeNanos();
361 if (safepoint_limit_time < current_time) {
362 tty->print_cr("# SafepointSynchronize: Finished after "
363 INT64_FORMAT_W(6) " ms",
364 ((current_time - safepoint_limit_time) / MICROUNITS +
365 SafepointTimeoutDelay));
366 }
367 }
368 #endif
369
370 assert((_safepoint_counter & 0x1) == 0, "must be even");
371 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
372 _safepoint_counter ++;
373
374 // Record state
375 _state = _synchronized;
376
377 OrderAccess::fence();
378
379 #ifdef ASSERT
380 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
381 // make sure all the threads were visited
382 assert(cur->was_visited_for_critical_count(), "missed a thread");
383 }
384 #endif // ASSERT
385
386 // Update the count of active JNI critical regions
387 GC_locker::set_jni_lock_count(_current_jni_active_count);
388
389 if (TraceSafepoint) {
390 VM_Operation *op = VMThread::vm_operation();
391 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
392 }
393
394 RuntimeService::record_safepoint_synchronized();
395 if (PrintSafepointStatistics) {
396 update_statistics_on_sync_end(os::javaTimeNanos());
397 }
398
399 // Call stuff that needs to be run when a safepoint is just about to be completed
400 do_cleanup_tasks();
401
402 if (PrintSafepointStatistics) {
403 // Record how much time spend on the above cleanup tasks
404 update_statistics_on_cleanup_end(os::javaTimeNanos());
405 }
406 }
407
408 // Wake up all threads, so they are ready to resume execution after the safepoint
409 // operation has been carried out
410 void SafepointSynchronize::end() {
411
412 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
413 assert((_safepoint_counter & 0x1) == 1, "must be odd");
414 _safepoint_counter ++;
415 // memory fence isn't required here since an odd _safepoint_counter
416 // value can do no harm and a fence is issued below anyway.
417
418 DEBUG_ONLY(Thread* myThread = Thread::current();)
419 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
420
421 if (PrintSafepointStatistics) {
422 end_statistics(os::javaTimeNanos());
423 }
424
425 #ifdef ASSERT
426 // A pending_exception cannot be installed during a safepoint. The threads
427 // may install an async exception after they come back from a safepoint into
428 // pending_exception after they unblock. But that should happen later.
429 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
430 assert (!(cur->has_pending_exception() &&
431 cur->safepoint_state()->is_at_poll_safepoint()),
432 "safepoint installed a pending exception");
433 }
434 #endif // ASSERT
435
436 if (PageArmed) {
437 // Make polling safepoint aware
438 os::make_polling_page_readable();
439 PageArmed = 0 ;
440 }
441
442 // Remove safepoint check from interpreter
443 Interpreter::ignore_safepoints();
444
445 {
446 MutexLocker mu(Safepoint_lock);
447
448 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
449
450 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
451 // when they get restarted.
452 _state = _not_synchronized;
453 OrderAccess::fence();
454
455 if (TraceSafepoint) {
456 tty->print_cr("Leaving safepoint region");
457 }
458
459 // Start suspended threads
460 for(JavaThread *current = Threads::first(); current; current = current->next()) {
461 // A problem occurring on Solaris is when attempting to restart threads
462 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
463 // to the next one (since it has been running the longest). We then have
464 // to wait for a cpu to become available before we can continue restarting
465 // threads.
466 // FIXME: This causes the performance of the VM to degrade when active and with
467 // large numbers of threads. Apparently this is due to the synchronous nature
468 // of suspending threads.
469 //
470 // TODO-FIXME: the comments above are vestigial and no longer apply.
471 // Furthermore, using solaris' schedctl in this particular context confers no benefit
472 if (VMThreadHintNoPreempt) {
473 os::hint_no_preempt();
474 }
475 ThreadSafepointState* cur_state = current->safepoint_state();
476 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
477 cur_state->restart();
478 assert(cur_state->is_running(), "safepoint state has not been reset");
479 }
480
481 RuntimeService::record_safepoint_end();
482
483 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
484 // blocked in signal_thread_blocked
485 Threads_lock->unlock();
486
487 }
488 #if INCLUDE_ALL_GCS
489 // If there are any concurrent GC threads resume them.
490 if (UseConcMarkSweepGC) {
491 ConcurrentMarkSweepThread::desynchronize(false);
492 } else if (UseG1GC) {
493 SuspendibleThreadSet::desynchronize();
494 }
495 #endif // INCLUDE_ALL_GCS
496 // record this time so VMThread can keep track how much time has elasped
497 // since last safepoint.
498 _end_of_last_safepoint = os::javaTimeMillis();
499 }
500
501 bool SafepointSynchronize::is_cleanup_needed() {
502 // Need a safepoint if some inline cache buffers is non-empty
503 if (!InlineCacheBuffer::is_empty()) return true;
504 return false;
505 }
506
507
508
509 // Various cleaning tasks that should be done periodically at safepoints
510 void SafepointSynchronize::do_cleanup_tasks() {
511 {
512 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime);
513 ObjectSynchronizer::deflate_idle_monitors();
514 }
515
516 {
517 TraceTime t2("updating inline caches", TraceSafepointCleanupTime);
518 InlineCacheBuffer::update_inline_caches();
519 }
520 {
521 TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime);
522 CompilationPolicy::policy()->do_safepoint_work();
523 }
524
525 {
526 TraceTime t4("mark nmethods", TraceSafepointCleanupTime);
527 NMethodSweeper::mark_active_nmethods();
528 }
529
530 if (SymbolTable::needs_rehashing()) {
531 TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime);
532 SymbolTable::rehash_table();
533 }
534
535 if (StringTable::needs_rehashing()) {
536 TraceTime t6("rehashing string table", TraceSafepointCleanupTime);
537 StringTable::rehash_table();
538 }
539
540 // rotate log files?
541 if (UseGCLogFileRotation) {
542 gclog_or_tty->rotate_log(false);
543 }
544
545 {
546 // CMS delays purging the CLDG until the beginning of the next safepoint and to
547 // make sure concurrent sweep is done
548 TraceTime t7("purging class loader data graph", TraceSafepointCleanupTime);
549 ClassLoaderDataGraph::purge_if_needed();
550 }
551 }
552
553
554 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
555 switch(state) {
556 case _thread_in_native:
557 // native threads are safe if they have no java stack or have walkable stack
558 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
559
560 // blocked threads should have already have walkable stack
561 case _thread_blocked:
562 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
563 return true;
564
565 default:
566 return false;
567 }
568 }
569
570
571 // See if the thread is running inside a lazy critical native and
572 // update the thread critical count if so. Also set a suspend flag to
573 // cause the native wrapper to return into the JVM to do the unlock
574 // once the native finishes.
575 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
576 if (state == _thread_in_native &&
577 thread->has_last_Java_frame() &&
578 thread->frame_anchor()->walkable()) {
579 // This thread might be in a critical native nmethod so look at
580 // the top of the stack and increment the critical count if it
581 // is.
582 frame wrapper_frame = thread->last_frame();
583 CodeBlob* stub_cb = wrapper_frame.cb();
584 if (stub_cb != NULL &&
585 stub_cb->is_nmethod() &&
586 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
587 // A thread could potentially be in a critical native across
588 // more than one safepoint, so only update the critical state on
589 // the first one. When it returns it will perform the unlock.
590 if (!thread->do_critical_native_unlock()) {
591 #ifdef ASSERT
592 if (!thread->in_critical()) {
593 GC_locker::increment_debug_jni_lock_count();
594 }
595 #endif
596 thread->enter_critical();
597 // Make sure the native wrapper calls back on return to
598 // perform the needed critical unlock.
599 thread->set_critical_native_unlock();
600 }
601 }
602 }
603 }
604
605
606
607 // -------------------------------------------------------------------------------------------------------
608 // Implementation of Safepoint callback point
609
610 void SafepointSynchronize::block(JavaThread *thread) {
611 assert(thread != NULL, "thread must be set");
612 assert(thread->is_Java_thread(), "not a Java thread");
613
614 // Threads shouldn't block if they are in the middle of printing, but...
615 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
616
617 // Only bail from the block() call if the thread is gone from the
618 // thread list; starting to exit should still block.
619 if (thread->is_terminated()) {
620 // block current thread if we come here from native code when VM is gone
621 thread->block_if_vm_exited();
622
623 // otherwise do nothing
624 return;
625 }
626
627 JavaThreadState state = thread->thread_state();
628 thread->frame_anchor()->make_walkable(thread);
629
630 // Check that we have a valid thread_state at this point
631 switch(state) {
632 case _thread_in_vm_trans:
633 case _thread_in_Java: // From compiled code
634
635 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
636 // we pretend we are still in the VM.
637 thread->set_thread_state(_thread_in_vm);
638
639 if (is_synchronizing()) {
640 Atomic::inc (&TryingToBlock) ;
641 }
642
643 // We will always be holding the Safepoint_lock when we are examine the state
644 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
645 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
646 Safepoint_lock->lock_without_safepoint_check();
647 if (is_synchronizing()) {
648 // Decrement the number of threads to wait for and signal vm thread
649 assert(_waiting_to_block > 0, "sanity check");
650 _waiting_to_block--;
651 thread->safepoint_state()->set_has_called_back(true);
652
653 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
654 if (thread->in_critical()) {
655 // Notice that this thread is in a critical section
656 increment_jni_active_count();
657 }
658
659 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
660 if (_waiting_to_block == 0) {
661 Safepoint_lock->notify_all();
662 }
663 }
664
665 // We transition the thread to state _thread_blocked here, but
666 // we can't do our usual check for external suspension and then
667 // self-suspend after the lock_without_safepoint_check() call
668 // below because we are often called during transitions while
669 // we hold different locks. That would leave us suspended while
670 // holding a resource which results in deadlocks.
671 thread->set_thread_state(_thread_blocked);
672 Safepoint_lock->unlock();
673
674 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
675 // the entire safepoint, the threads will all line up here during the safepoint.
676 Threads_lock->lock_without_safepoint_check();
677 // restore original state. This is important if the thread comes from compiled code, so it
678 // will continue to execute with the _thread_in_Java state.
679 thread->set_thread_state(state);
680 Threads_lock->unlock();
681 break;
682
683 case _thread_in_native_trans:
684 case _thread_blocked_trans:
685 case _thread_new_trans:
686 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
687 thread->print_thread_state();
688 fatal("Deadlock in safepoint code. "
689 "Should have called back to the VM before blocking.");
690 }
691
692 // We transition the thread to state _thread_blocked here, but
693 // we can't do our usual check for external suspension and then
694 // self-suspend after the lock_without_safepoint_check() call
695 // below because we are often called during transitions while
696 // we hold different locks. That would leave us suspended while
697 // holding a resource which results in deadlocks.
698 thread->set_thread_state(_thread_blocked);
699
700 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
701 // the safepoint code might still be waiting for it to block. We need to change the state here,
702 // so it can see that it is at a safepoint.
703
704 // Block until the safepoint operation is completed.
705 Threads_lock->lock_without_safepoint_check();
706
707 // Restore state
708 thread->set_thread_state(state);
709
710 Threads_lock->unlock();
711 break;
712
713 default:
714 fatal(err_msg("Illegal threadstate encountered: %d", state));
715 }
716
717 // Check for pending. async. exceptions or suspends - except if the
718 // thread was blocked inside the VM. has_special_runtime_exit_condition()
719 // is called last since it grabs a lock and we only want to do that when
720 // we must.
721 //
722 // Note: we never deliver an async exception at a polling point as the
723 // compiler may not have an exception handler for it. The polling
724 // code will notice the async and deoptimize and the exception will
725 // be delivered. (Polling at a return point is ok though). Sure is
726 // a lot of bother for a deprecated feature...
727 //
728 // We don't deliver an async exception if the thread state is
729 // _thread_in_native_trans so JNI functions won't be called with
730 // a surprising pending exception. If the thread state is going back to java,
731 // async exception is checked in check_special_condition_for_native_trans().
732
733 if (state != _thread_blocked_trans &&
734 state != _thread_in_vm_trans &&
735 thread->has_special_runtime_exit_condition()) {
736 thread->handle_special_runtime_exit_condition(
737 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
738 }
739 }
740
741 // ------------------------------------------------------------------------------------------------------
742 // Exception handlers
743
744 #ifndef PRODUCT
745
746 #ifdef SPARC
747
748 #ifdef _LP64
749 #define PTR_PAD ""
750 #else
751 #define PTR_PAD " "
752 #endif
753
754 static void print_ptrs(intptr_t oldptr, intptr_t newptr, bool wasoop) {
755 bool is_oop = newptr ? (cast_to_oop(newptr))->is_oop() : false;
756 tty->print_cr(PTR_FORMAT PTR_PAD " %s %c " PTR_FORMAT PTR_PAD " %s %s",
757 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!',
758 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" "));
759 }
760
761 static void print_longs(jlong oldptr, jlong newptr, bool wasoop) {
762 bool is_oop = newptr ? (cast_to_oop(newptr))->is_oop() : false;
763 tty->print_cr(PTR64_FORMAT " %s %c " PTR64_FORMAT " %s %s",
764 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!',
765 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" "));
766 }
767
768 static void print_me(intptr_t *new_sp, intptr_t *old_sp, bool *was_oops) {
769 #ifdef _LP64
770 tty->print_cr("--------+------address-----+------before-----------+-------after----------+");
771 const int incr = 1; // Increment to skip a long, in units of intptr_t
772 #else
773 tty->print_cr("--------+--address-+------before-----------+-------after----------+");
774 const int incr = 2; // Increment to skip a long, in units of intptr_t
775 #endif
776 tty->print_cr("---SP---|");
777 for( int i=0; i<16; i++ ) {
778 tty->print("blob %c%d |"PTR_FORMAT" ","LO"[i>>3],i&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
779 tty->print_cr("--------|");
780 for( int i1=0; i1<frame::memory_parameter_word_sp_offset-16; i1++ ) {
781 tty->print("argv pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
782 tty->print(" pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++);
783 tty->print_cr("--------|");
784 tty->print(" G1 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr;
785 tty->print(" G3 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr;
786 tty->print(" G4 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr;
787 tty->print(" G5 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr;
788 tty->print_cr(" FSR |"PTR_FORMAT" "PTR64_FORMAT" "PTR64_FORMAT,new_sp,*(jlong*)old_sp,*(jlong*)new_sp);
789 old_sp += incr; new_sp += incr; was_oops += incr;
790 // Skip the floats
791 tty->print_cr("--Float-|"PTR_FORMAT,new_sp);
792 tty->print_cr("---FP---|");
793 old_sp += incr*32; new_sp += incr*32; was_oops += incr*32;
794 for( int i2=0; i2<16; i2++ ) {
795 tty->print("call %c%d |"PTR_FORMAT" ","LI"[i2>>3],i2&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
796 tty->cr();
797 }
798 #endif // SPARC
799 #endif // PRODUCT
800
801
802 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
803 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
804 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
805 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
806
807 // Uncomment this to get some serious before/after printing of the
808 // Sparc safepoint-blob frame structure.
809 /*
810 intptr_t* sp = thread->last_Java_sp();
811 intptr_t stack_copy[150];
812 for( int i=0; i<150; i++ ) stack_copy[i] = sp[i];
813 bool was_oops[150];
814 for( int i=0; i<150; i++ )
815 was_oops[i] = stack_copy[i] ? ((oop)stack_copy[i])->is_oop() : false;
816 */
817
818 if (ShowSafepointMsgs) {
819 tty->print("handle_polling_page_exception: ");
820 }
821
822 if (PrintSafepointStatistics) {
823 inc_page_trap_count();
824 }
825
826 ThreadSafepointState* state = thread->safepoint_state();
827
828 state->handle_polling_page_exception();
829 // print_me(sp,stack_copy,was_oops);
830 }
831
832
833 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
834 if (!timeout_error_printed) {
835 timeout_error_printed = true;
836 // Print out the thread infor which didn't reach the safepoint for debugging
837 // purposes (useful when there are lots of threads in the debugger).
838 tty->cr();
839 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
840 if (reason == _spinning_timeout) {
841 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
842 } else if (reason == _blocking_timeout) {
843 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
844 }
845
846 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
847 ThreadSafepointState *cur_state;
848 ResourceMark rm;
849 for(JavaThread *cur_thread = Threads::first(); cur_thread;
850 cur_thread = cur_thread->next()) {
851 cur_state = cur_thread->safepoint_state();
852
853 if (cur_thread->thread_state() != _thread_blocked &&
854 ((reason == _spinning_timeout && cur_state->is_running()) ||
855 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
856 tty->print("# ");
857 cur_thread->print();
858 tty->cr();
859 }
860 }
861 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
862 }
863
864 // To debug the long safepoint, specify both DieOnSafepointTimeout &
865 // ShowMessageBoxOnError.
866 if (DieOnSafepointTimeout) {
867 char msg[1024];
868 VM_Operation *op = VMThread::vm_operation();
869 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
870 SafepointTimeoutDelay,
871 op != NULL ? op->name() : "no vm operation");
872 fatal(msg);
873 }
874 }
875
876
877 // -------------------------------------------------------------------------------------------------------
878 // Implementation of ThreadSafepointState
879
880 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
881 _thread = thread;
882 _type = _running;
883 _has_called_back = false;
884 _at_poll_safepoint = false;
885 }
886
887 void ThreadSafepointState::create(JavaThread *thread) {
888 ThreadSafepointState *state = new ThreadSafepointState(thread);
889 thread->set_safepoint_state(state);
890 }
891
892 void ThreadSafepointState::destroy(JavaThread *thread) {
893 if (thread->safepoint_state()) {
894 delete(thread->safepoint_state());
895 thread->set_safepoint_state(NULL);
896 }
897 }
898
899 void ThreadSafepointState::examine_state_of_thread() {
900 assert(is_running(), "better be running or just have hit safepoint poll");
901
902 JavaThreadState state = _thread->thread_state();
903
904 // Save the state at the start of safepoint processing.
905 _orig_thread_state = state;
906
907 // Check for a thread that is suspended. Note that thread resume tries
908 // to grab the Threads_lock which we own here, so a thread cannot be
909 // resumed during safepoint synchronization.
910
911 // We check to see if this thread is suspended without locking to
912 // avoid deadlocking with a third thread that is waiting for this
913 // thread to be suspended. The third thread can notice the safepoint
914 // that we're trying to start at the beginning of its SR_lock->wait()
915 // call. If that happens, then the third thread will block on the
916 // safepoint while still holding the underlying SR_lock. We won't be
917 // able to get the SR_lock and we'll deadlock.
918 //
919 // We don't need to grab the SR_lock here for two reasons:
920 // 1) The suspend flags are both volatile and are set with an
921 // Atomic::cmpxchg() call so we should see the suspended
922 // state right away.
923 // 2) We're being called from the safepoint polling loop; if
924 // we don't see the suspended state on this iteration, then
925 // we'll come around again.
926 //
927 bool is_suspended = _thread->is_ext_suspended();
928 if (is_suspended) {
929 roll_forward(_at_safepoint);
930 return;
931 }
932
933 // Some JavaThread states have an initial safepoint state of
934 // running, but are actually at a safepoint. We will happily
935 // agree and update the safepoint state here.
936 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
937 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
938 roll_forward(_at_safepoint);
939 return;
940 }
941
942 if (state == _thread_in_vm) {
943 roll_forward(_call_back);
944 return;
945 }
946
947 // All other thread states will continue to run until they
948 // transition and self-block in state _blocked
949 // Safepoint polling in compiled code causes the Java threads to do the same.
950 // Note: new threads may require a malloc so they must be allowed to finish
951
952 assert(is_running(), "examine_state_of_thread on non-running thread");
953 return;
954 }
955
956 // Returns true is thread could not be rolled forward at present position.
957 void ThreadSafepointState::roll_forward(suspend_type type) {
958 _type = type;
959
960 switch(_type) {
961 case _at_safepoint:
962 SafepointSynchronize::signal_thread_at_safepoint();
963 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
964 if (_thread->in_critical()) {
965 // Notice that this thread is in a critical section
966 SafepointSynchronize::increment_jni_active_count();
967 }
968 break;
969
970 case _call_back:
971 set_has_called_back(false);
972 break;
973
974 case _running:
975 default:
976 ShouldNotReachHere();
977 }
978 }
979
980 void ThreadSafepointState::restart() {
981 switch(type()) {
982 case _at_safepoint:
983 case _call_back:
984 break;
985
986 case _running:
987 default:
988 tty->print_cr("restart thread "INTPTR_FORMAT" with state %d",
989 _thread, _type);
990 _thread->print();
991 ShouldNotReachHere();
992 }
993 _type = _running;
994 set_has_called_back(false);
995 }
996
997
998 void ThreadSafepointState::print_on(outputStream *st) const {
999 const char *s;
1000
1001 switch(_type) {
1002 case _running : s = "_running"; break;
1003 case _at_safepoint : s = "_at_safepoint"; break;
1004 case _call_back : s = "_call_back"; break;
1005 default:
1006 ShouldNotReachHere();
1007 }
1008
1009 st->print_cr("Thread: " INTPTR_FORMAT
1010 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1011 _thread, _thread->osthread()->thread_id(), s, _has_called_back,
1012 _at_poll_safepoint);
1013
1014 _thread->print_thread_state_on(st);
1015 }
1016
1017
1018 // ---------------------------------------------------------------------------------------------------------------------
1019
1020 // Block the thread at the safepoint poll or poll return.
1021 void ThreadSafepointState::handle_polling_page_exception() {
1022
1023 // Check state. block() will set thread state to thread_in_vm which will
1024 // cause the safepoint state _type to become _call_back.
1025 assert(type() == ThreadSafepointState::_running,
1026 "polling page exception on thread not running state");
1027
1028 // Step 1: Find the nmethod from the return address
1029 if (ShowSafepointMsgs && Verbose) {
1030 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
1031 }
1032 address real_return_addr = thread()->saved_exception_pc();
1033
1034 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1035 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
1036 nmethod* nm = (nmethod*)cb;
1037
1038 // Find frame of caller
1039 frame stub_fr = thread()->last_frame();
1040 CodeBlob* stub_cb = stub_fr.cb();
1041 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1042 RegisterMap map(thread(), true);
1043 frame caller_fr = stub_fr.sender(&map);
1044
1045 // Should only be poll_return or poll
1046 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1047
1048 // This is a poll immediately before a return. The exception handling code
1049 // has already had the effect of causing the return to occur, so the execution
1050 // will continue immediately after the call. In addition, the oopmap at the
1051 // return point does not mark the return value as an oop (if it is), so
1052 // it needs a handle here to be updated.
1053 if( nm->is_at_poll_return(real_return_addr) ) {
1054 // See if return type is an oop.
1055 bool return_oop = nm->method()->is_returning_oop();
1056 Handle return_value;
1057 if (return_oop) {
1058 // The oop result has been saved on the stack together with all
1059 // the other registers. In order to preserve it over GCs we need
1060 // to keep it in a handle.
1061 oop result = caller_fr.saved_oop_result(&map);
1062 assert(result == NULL || result->is_oop(), "must be oop");
1063 return_value = Handle(thread(), result);
1064 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1065 }
1066
1067 // Block the thread
1068 SafepointSynchronize::block(thread());
1069
1070 // restore oop result, if any
1071 if (return_oop) {
1072 caller_fr.set_saved_oop_result(&map, return_value());
1073 }
1074 }
1075
1076 // This is a safepoint poll. Verify the return address and block.
1077 else {
1078 set_at_poll_safepoint(true);
1079
1080 // verify the blob built the "return address" correctly
1081 assert(real_return_addr == caller_fr.pc(), "must match");
1082
1083 // Block the thread
1084 SafepointSynchronize::block(thread());
1085 set_at_poll_safepoint(false);
1086
1087 // If we have a pending async exception deoptimize the frame
1088 // as otherwise we may never deliver it.
1089 if (thread()->has_async_condition()) {
1090 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1091 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1092 }
1093
1094 // If an exception has been installed we must check for a pending deoptimization
1095 // Deoptimize frame if exception has been thrown.
1096
1097 if (thread()->has_pending_exception() ) {
1098 RegisterMap map(thread(), true);
1099 frame caller_fr = stub_fr.sender(&map);
1100 if (caller_fr.is_deoptimized_frame()) {
1101 // The exception patch will destroy registers that are still
1102 // live and will be needed during deoptimization. Defer the
1103 // Async exception should have defered the exception until the
1104 // next safepoint which will be detected when we get into
1105 // the interpreter so if we have an exception now things
1106 // are messed up.
1107
1108 fatal("Exception installed and deoptimization is pending");
1109 }
1110 }
1111 }
1112 }
1113
1114
1115 //
1116 // Statistics & Instrumentations
1117 //
1118 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1119 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1120 int SafepointSynchronize::_cur_stat_index = 0;
1121 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1122 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1123 jlong SafepointSynchronize::_max_sync_time = 0;
1124 jlong SafepointSynchronize::_max_vmop_time = 0;
1125 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1126
1127 static jlong cleanup_end_time = 0;
1128 static bool need_to_track_page_armed_status = false;
1129 static bool init_done = false;
1130
1131 // Helper method to print the header.
1132 static void print_header() {
1133 tty->print(" vmop "
1134 "[threads: total initially_running wait_to_block] ");
1135 tty->print("[time: spin block sync cleanup vmop] ");
1136
1137 // no page armed status printed out if it is always armed.
1138 if (need_to_track_page_armed_status) {
1139 tty->print("page_armed ");
1140 }
1141
1142 tty->print_cr("page_trap_count");
1143 }
1144
1145 void SafepointSynchronize::deferred_initialize_stat() {
1146 if (init_done) return;
1147
1148 if (PrintSafepointStatisticsCount <= 0) {
1149 fatal("Wrong PrintSafepointStatisticsCount");
1150 }
1151
1152 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1153 // be printed right away, in which case, _safepoint_stats will regress to
1154 // a single element array. Otherwise, it is a circular ring buffer with default
1155 // size of PrintSafepointStatisticsCount.
1156 int stats_array_size;
1157 if (PrintSafepointStatisticsTimeout > 0) {
1158 stats_array_size = 1;
1159 PrintSafepointStatistics = true;
1160 } else {
1161 stats_array_size = PrintSafepointStatisticsCount;
1162 }
1163 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1164 * sizeof(SafepointStats), mtInternal);
1165 guarantee(_safepoint_stats != NULL,
1166 "not enough memory for safepoint instrumentation data");
1167
1168 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
1169 need_to_track_page_armed_status = true;
1170 }
1171 init_done = true;
1172 }
1173
1174 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1175 assert(init_done, "safepoint statistics array hasn't been initialized");
1176 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1177
1178 spstat->_time_stamp = _ts_of_current_safepoint;
1179
1180 VM_Operation *op = VMThread::vm_operation();
1181 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1182 if (op != NULL) {
1183 _safepoint_reasons[spstat->_vmop_type]++;
1184 }
1185
1186 spstat->_nof_total_threads = nof_threads;
1187 spstat->_nof_initial_running_threads = nof_running;
1188 spstat->_nof_threads_hit_page_trap = 0;
1189
1190 // Records the start time of spinning. The real time spent on spinning
1191 // will be adjusted when spin is done. Same trick is applied for time
1192 // spent on waiting for threads to block.
1193 if (nof_running != 0) {
1194 spstat->_time_to_spin = os::javaTimeNanos();
1195 } else {
1196 spstat->_time_to_spin = 0;
1197 }
1198 }
1199
1200 void SafepointSynchronize::update_statistics_on_spin_end() {
1201 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1202
1203 jlong cur_time = os::javaTimeNanos();
1204
1205 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1206 if (spstat->_nof_initial_running_threads != 0) {
1207 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1208 }
1209
1210 if (need_to_track_page_armed_status) {
1211 spstat->_page_armed = (PageArmed == 1);
1212 }
1213
1214 // Records the start time of waiting for to block. Updated when block is done.
1215 if (_waiting_to_block != 0) {
1216 spstat->_time_to_wait_to_block = cur_time;
1217 } else {
1218 spstat->_time_to_wait_to_block = 0;
1219 }
1220 }
1221
1222 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1223 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1224
1225 if (spstat->_nof_threads_wait_to_block != 0) {
1226 spstat->_time_to_wait_to_block = end_time -
1227 spstat->_time_to_wait_to_block;
1228 }
1229
1230 // Records the end time of sync which will be used to calculate the total
1231 // vm operation time. Again, the real time spending in syncing will be deducted
1232 // from the start of the sync time later when end_statistics is called.
1233 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1234 if (spstat->_time_to_sync > _max_sync_time) {
1235 _max_sync_time = spstat->_time_to_sync;
1236 }
1237
1238 spstat->_time_to_do_cleanups = end_time;
1239 }
1240
1241 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1242 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1243
1244 // Record how long spent in cleanup tasks.
1245 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1246
1247 cleanup_end_time = end_time;
1248 }
1249
1250 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1251 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1252
1253 // Update the vm operation time.
1254 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1255 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1256 _max_vmop_time = spstat->_time_to_exec_vmop;
1257 }
1258 // Only the sync time longer than the specified
1259 // PrintSafepointStatisticsTimeout will be printed out right away.
1260 // By default, it is -1 meaning all samples will be put into the list.
1261 if ( PrintSafepointStatisticsTimeout > 0) {
1262 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1263 print_statistics();
1264 }
1265 } else {
1266 // The safepoint statistics will be printed out when the _safepoin_stats
1267 // array fills up.
1268 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1269 print_statistics();
1270 _cur_stat_index = 0;
1271 } else {
1272 _cur_stat_index++;
1273 }
1274 }
1275 }
1276
1277 void SafepointSynchronize::print_statistics() {
1278 SafepointStats* sstats = _safepoint_stats;
1279
1280 for (int index = 0; index <= _cur_stat_index; index++) {
1281 if (index % 30 == 0) {
1282 print_header();
1283 }
1284 sstats = &_safepoint_stats[index];
1285 tty->print("%.3f: ", sstats->_time_stamp);
1286 tty->print("%-26s ["
1287 INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15)
1288 " ] ",
1289 sstats->_vmop_type == -1 ? "no vm operation" :
1290 VM_Operation::name(sstats->_vmop_type),
1291 sstats->_nof_total_threads,
1292 sstats->_nof_initial_running_threads,
1293 sstats->_nof_threads_wait_to_block);
1294 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1295 tty->print(" ["
1296 INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1297 INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1298 INT64_FORMAT_W(6)" ] ",
1299 sstats->_time_to_spin / MICROUNITS,
1300 sstats->_time_to_wait_to_block / MICROUNITS,
1301 sstats->_time_to_sync / MICROUNITS,
1302 sstats->_time_to_do_cleanups / MICROUNITS,
1303 sstats->_time_to_exec_vmop / MICROUNITS);
1304
1305 if (need_to_track_page_armed_status) {
1306 tty->print(INT32_FORMAT" ", sstats->_page_armed);
1307 }
1308 tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap);
1309 }
1310 }
1311
1312 // This method will be called when VM exits. It will first call
1313 // print_statistics to print out the rest of the sampling. Then
1314 // it tries to summarize the sampling.
1315 void SafepointSynchronize::print_stat_on_exit() {
1316 if (_safepoint_stats == NULL) return;
1317
1318 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1319
1320 // During VM exit, end_statistics may not get called and in that
1321 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1322 // don't print it out.
1323 // Approximate the vm op time.
1324 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1325 os::javaTimeNanos() - cleanup_end_time;
1326
1327 if ( PrintSafepointStatisticsTimeout < 0 ||
1328 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1329 print_statistics();
1330 }
1331 tty->cr();
1332
1333 // Print out polling page sampling status.
1334 if (!need_to_track_page_armed_status) {
1335 if (UseCompilerSafepoints) {
1336 tty->print_cr("Polling page always armed");
1337 }
1338 } else {
1339 tty->print_cr("Defer polling page loop count = %d\n",
1340 DeferPollingPageLoopCount);
1341 }
1342
1343 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1344 if (_safepoint_reasons[index] != 0) {
1345 tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index),
1346 _safepoint_reasons[index]);
1347 }
1348 }
1349
1350 tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint",
1351 _coalesced_vmop_count);
1352 tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms",
1353 _max_sync_time / MICROUNITS);
1354 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1355 INT64_FORMAT_W(5)" ms",
1356 _max_vmop_time / MICROUNITS);
1357 }
1358
1359 // ------------------------------------------------------------------------------------------------
1360 // Non-product code
1361
1362 #ifndef PRODUCT
1363
1364 void SafepointSynchronize::print_state() {
1365 if (_state == _not_synchronized) {
1366 tty->print_cr("not synchronized");
1367 } else if (_state == _synchronizing || _state == _synchronized) {
1368 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1369 "synchronized");
1370
1371 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1372 cur->safepoint_state()->print();
1373 }
1374 }
1375 }
1376
1377 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1378 if (ShowSafepointMsgs) {
1379 va_list ap;
1380 va_start(ap, format);
1381 tty->vprint_cr(format, ap);
1382 va_end(ap);
1383 }
1384 }
1385
1386 #endif // !PRODUCT