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