1 /*
2 * Copyright (c) 1997, 2015, 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/stringTable.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/shared/collectedHeap.hpp"
34 #include "gc/shared/gcLocker.inline.hpp"
35 #include "interpreter/interpreter.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 #if INCLUDE_ALL_GCS
59 #include "gc/shenandoah/shenandoahConcurrentThread.hpp"
60 #include "gc/cms/concurrentMarkSweepThread.hpp"
61 #include "gc/g1/suspendibleThreadSet.hpp"
62 #endif // INCLUDE_ALL_GCS
63 #ifdef COMPILER1
64 #include "c1/c1_globals.hpp"
65 #endif
66
67 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
68
69 // --------------------------------------------------------------------------------------------------
70 // Implementation of Safepoint begin/end
71
72 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
73 volatile int SafepointSynchronize::_waiting_to_block = 0;
74 volatile int SafepointSynchronize::_safepoint_counter = 0;
75 int SafepointSynchronize::_current_jni_active_count = 0;
76 long SafepointSynchronize::_end_of_last_safepoint = 0;
77 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
78 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
79 static bool timeout_error_printed = false;
80
81 // Roll all threads forward to a safepoint and suspend them all
82 void SafepointSynchronize::begin() {
83
84 Thread* myThread = Thread::current();
85 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
86
87 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
88 _safepoint_begin_time = os::javaTimeNanos();
89 _ts_of_current_safepoint = tty->time_stamp().seconds();
90 }
91
92 #if INCLUDE_ALL_GCS
93 if (UseConcMarkSweepGC) {
94 // In the future we should investigate whether CMS can use the
95 // more-general mechanism below. DLD (01/05).
96 ConcurrentMarkSweepThread::synchronize(false);
97 } else if (UseG1GC) {
98 SuspendibleThreadSet::synchronize();
99 } else if (UseShenandoahGC) {
100 ShenandoahConcurrentThread::safepoint_synchronize();
101 }
102
103 #endif // INCLUDE_ALL_GCS
104
105 // By getting the Threads_lock, we assure that no threads are about to start or
106 // exit. It is released again in SafepointSynchronize::end().
107 Threads_lock->lock();
108
109 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
110
111 int nof_threads = Threads::number_of_threads();
112
113 if (TraceSafepoint) {
114 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
115 }
116
117 RuntimeService::record_safepoint_begin();
118
119 MutexLocker mu(Safepoint_lock);
120
121 // Reset the count of active JNI critical threads
122 _current_jni_active_count = 0;
123
124 // Set number of threads to wait for, before we initiate the callbacks
125 _waiting_to_block = nof_threads;
126 TryingToBlock = 0 ;
127 int still_running = nof_threads;
128
129 // Save the starting time, so that it can be compared to see if this has taken
130 // too long to complete.
131 jlong safepoint_limit_time;
132 timeout_error_printed = false;
133
134 // PrintSafepointStatisticsTimeout can be specified separately. When
135 // specified, PrintSafepointStatistics will be set to true in
136 // deferred_initialize_stat method. The initialization has to be done
137 // early enough to avoid any races. See bug 6880029 for details.
138 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
139 deferred_initialize_stat();
140 }
141
142 // Begin the process of bringing the system to a safepoint.
143 // Java threads can be in several different states and are
144 // stopped by different mechanisms:
145 //
146 // 1. Running interpreted
147 // The interpreter dispatch table is changed to force it to
148 // check for a safepoint condition between bytecodes.
149 // 2. Running in native code
150 // When returning from the native code, a Java thread must check
151 // the safepoint _state to see if we must block. If the
152 // VM thread sees a Java thread in native, it does
153 // not wait for this thread to block. The order of the memory
154 // writes and reads of both the safepoint state and the Java
155 // threads state is critical. In order to guarantee that the
156 // memory writes are serialized with respect to each other,
157 // the VM thread issues a memory barrier instruction
158 // (on MP systems). In order to avoid the overhead of issuing
159 // a memory barrier for each Java thread making native calls, each Java
160 // thread performs a write to a single memory page after changing
161 // the thread state. The VM thread performs a sequence of
162 // mprotect OS calls which forces all previous writes from all
163 // Java threads to be serialized. This is done in the
164 // os::serialize_thread_states() call. This has proven to be
165 // much more efficient than executing a membar instruction
166 // on every call to native code.
167 // 3. Running compiled Code
168 // Compiled code reads a global (Safepoint Polling) page that
169 // is set to fault if we are trying to get to a safepoint.
170 // 4. Blocked
171 // A thread which is blocked will not be allowed to return from the
172 // block condition until the safepoint operation is complete.
173 // 5. In VM or Transitioning between states
174 // If a Java thread is currently running in the VM or transitioning
175 // between states, the safepointing code will wait for the thread to
176 // block itself when it attempts transitions to a new state.
177 //
178 _state = _synchronizing;
179 OrderAccess::fence();
180
181 // Flush all thread states to memory
182 if (!UseMembar) {
183 os::serialize_thread_states();
184 }
185
186 // Make interpreter safepoint aware
187 Interpreter::notice_safepoints();
188
189 if (DeferPollingPageLoopCount < 0) {
190 // Make polling safepoint aware
191 guarantee (PageArmed == 0, "invariant") ;
192 PageArmed = 1 ;
193 os::make_polling_page_unreadable();
194 }
195
196 // Consider using active_processor_count() ... but that call is expensive.
197 int ncpus = os::processor_count() ;
198
199 #ifdef ASSERT
200 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
201 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
202 // Clear the visited flag to ensure that the critical counts are collected properly.
203 cur->set_visited_for_critical_count(false);
204 }
205 #endif // ASSERT
206
207 if (SafepointTimeout)
208 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
209
210 // Iterate through all threads until it have been determined how to stop them all at a safepoint
211 unsigned int iterations = 0;
212 int steps = 0 ;
213 while(still_running > 0) {
214 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
215 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
216 ThreadSafepointState *cur_state = cur->safepoint_state();
217 if (cur_state->is_running()) {
218 cur_state->examine_state_of_thread();
219 if (!cur_state->is_running()) {
220 still_running--;
221 // consider adjusting steps downward:
222 // steps = 0
223 // steps -= NNN
224 // steps >>= 1
225 // steps = MIN(steps, 2000-100)
226 // if (iterations != 0) steps -= NNN
227 }
228 if (TraceSafepoint && Verbose) cur_state->print();
229 }
230 }
231
232 if (PrintSafepointStatistics && iterations == 0) {
233 begin_statistics(nof_threads, still_running);
234 }
235
236 if (still_running > 0) {
237 // Check for if it takes to long
238 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
239 print_safepoint_timeout(_spinning_timeout);
240 }
241
242 // Spin to avoid context switching.
243 // There's a tension between allowing the mutators to run (and rendezvous)
244 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
245 // a mutator might otherwise use profitably to reach a safepoint. Excessive
246 // spinning by the VM thread on a saturated system can increase rendezvous latency.
247 // Blocking or yielding incur their own penalties in the form of context switching
248 // and the resultant loss of $ residency.
249 //
250 // Further complicating matters is that yield() does not work as naively expected
251 // on many platforms -- yield() does not guarantee that any other ready threads
252 // will run. As such we revert to naked_short_sleep() after some number of iterations.
253 // nakes_short_sleep() is implemented as a short unconditional sleep.
254 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
255 // can actually increase the time it takes the VM thread to detect that a system-wide
256 // stop-the-world safepoint has been reached. In a pathological scenario such as that
257 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
258 // In that case the mutators will be stalled waiting for the safepoint to complete and the
259 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
260 // will eventually wake up and detect that all mutators are safe, at which point
261 // we'll again make progress.
262 //
263 // Beware too that that the VMThread typically runs at elevated priority.
264 // Its default priority is higher than the default mutator priority.
265 // Obviously, this complicates spinning.
266 //
267 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
268 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
269 //
270 // See the comments in synchronizer.cpp for additional remarks on spinning.
271 //
272 // In the future we might:
273 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
274 // This is tricky as the path used by a thread exiting the JVM (say on
275 // on JNI call-out) simply stores into its state field. The burden
276 // is placed on the VM thread, which must poll (spin).
277 // 2. Find something useful to do while spinning. If the safepoint is GC-related
278 // we might aggressively scan the stacks of threads that are already safe.
279 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
280 // If all the mutators are ONPROC there's no reason to sleep or yield.
281 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
282 // 5. Check system saturation. If the system is not fully saturated then
283 // simply spin and avoid sleep/yield.
284 // 6. As still-running mutators rendezvous they could unpark the sleeping
285 // VMthread. This works well for still-running mutators that become
286 // safe. The VMthread must still poll for mutators that call-out.
287 // 7. Drive the policy on time-since-begin instead of iterations.
288 // 8. Consider making the spin duration a function of the # of CPUs:
289 // Spin = (((ncpus-1) * M) + K) + F(still_running)
290 // Alternately, instead of counting iterations of the outer loop
291 // we could count the # of threads visited in the inner loop, above.
292 // 9. On windows consider using the return value from SwitchThreadTo()
293 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
294
295 if (int(iterations) == DeferPollingPageLoopCount) {
296 guarantee (PageArmed == 0, "invariant") ;
297 PageArmed = 1 ;
298 os::make_polling_page_unreadable();
299 }
300
301 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
302 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
303 ++steps ;
304 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
305 SpinPause() ; // MP-Polite spin
306 } else
307 if (steps < DeferThrSuspendLoopCount) {
308 os::naked_yield() ;
309 } else {
310 os::naked_short_sleep(1);
311 }
312
313 iterations ++ ;
314 }
315 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
316 }
317 assert(still_running == 0, "sanity check");
318
319 if (PrintSafepointStatistics) {
320 update_statistics_on_spin_end();
321 }
322
323 // wait until all threads are stopped
324 while (_waiting_to_block > 0) {
325 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
326 if (!SafepointTimeout || timeout_error_printed) {
327 Safepoint_lock->wait(true); // true, means with no safepoint checks
328 } else {
329 // Compute remaining time
330 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
331
332 // If there is no remaining time, then there is an error
333 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
334 print_safepoint_timeout(_blocking_timeout);
335 }
336 }
337 }
338 assert(_waiting_to_block == 0, "sanity check");
339
340 #ifndef PRODUCT
341 if (SafepointTimeout) {
342 jlong current_time = os::javaTimeNanos();
343 if (safepoint_limit_time < current_time) {
344 tty->print_cr("# SafepointSynchronize: Finished after "
345 INT64_FORMAT_W(6) " ms",
346 ((current_time - safepoint_limit_time) / MICROUNITS +
347 SafepointTimeoutDelay));
348 }
349 }
350 #endif
351
352 assert((_safepoint_counter & 0x1) == 0, "must be even");
353 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
354 _safepoint_counter ++;
355
356 // Record state
357 _state = _synchronized;
358
359 OrderAccess::fence();
360
361 #ifdef ASSERT
362 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
363 // make sure all the threads were visited
364 assert(cur->was_visited_for_critical_count(), "missed a thread");
365 }
366 #endif // ASSERT
367
368 // Update the count of active JNI critical regions
369 GC_locker::set_jni_lock_count(_current_jni_active_count);
370
371 if (TraceSafepoint) {
372 VM_Operation *op = VMThread::vm_operation();
373 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
374 }
375
376 RuntimeService::record_safepoint_synchronized();
377 if (PrintSafepointStatistics) {
378 update_statistics_on_sync_end(os::javaTimeNanos());
379 }
380
381 // Call stuff that needs to be run when a safepoint is just about to be completed
382 do_cleanup_tasks();
383
384 if (PrintSafepointStatistics) {
385 // Record how much time spend on the above cleanup tasks
386 update_statistics_on_cleanup_end(os::javaTimeNanos());
387 }
388 }
389
390 // Wake up all threads, so they are ready to resume execution after the safepoint
391 // operation has been carried out
392 void SafepointSynchronize::end() {
393
394 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
395 assert((_safepoint_counter & 0x1) == 1, "must be odd");
396 _safepoint_counter ++;
397 // memory fence isn't required here since an odd _safepoint_counter
398 // value can do no harm and a fence is issued below anyway.
399
400 DEBUG_ONLY(Thread* myThread = Thread::current();)
401 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
402
403 if (PrintSafepointStatistics) {
404 end_statistics(os::javaTimeNanos());
405 }
406
407 #ifdef ASSERT
408 // A pending_exception cannot be installed during a safepoint. The threads
409 // may install an async exception after they come back from a safepoint into
410 // pending_exception after they unblock. But that should happen later.
411 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
412 assert (!(cur->has_pending_exception() &&
413 cur->safepoint_state()->is_at_poll_safepoint()),
414 "safepoint installed a pending exception");
415 }
416 #endif // ASSERT
417
418 if (PageArmed) {
419 // Make polling safepoint aware
420 os::make_polling_page_readable();
421 PageArmed = 0 ;
422 }
423
424 // Remove safepoint check from interpreter
425 Interpreter::ignore_safepoints();
426
427 {
428 MutexLocker mu(Safepoint_lock);
429
430 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
431
432 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
433 // when they get restarted.
434 _state = _not_synchronized;
435 OrderAccess::fence();
436
437 if (TraceSafepoint) {
438 tty->print_cr("Leaving safepoint region");
439 }
440
441 // Start suspended threads
442 for(JavaThread *current = Threads::first(); current; current = current->next()) {
443 // A problem occurring on Solaris is when attempting to restart threads
444 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
445 // to the next one (since it has been running the longest). We then have
446 // to wait for a cpu to become available before we can continue restarting
447 // threads.
448 // FIXME: This causes the performance of the VM to degrade when active and with
449 // large numbers of threads. Apparently this is due to the synchronous nature
450 // of suspending threads.
451 //
452 // TODO-FIXME: the comments above are vestigial and no longer apply.
453 // Furthermore, using solaris' schedctl in this particular context confers no benefit
454 if (VMThreadHintNoPreempt) {
455 os::hint_no_preempt();
456 }
457 ThreadSafepointState* cur_state = current->safepoint_state();
458 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
459 cur_state->restart();
460 assert(cur_state->is_running(), "safepoint state has not been reset");
461 }
462
463 RuntimeService::record_safepoint_end();
464
465 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
466 // blocked in signal_thread_blocked
467 Threads_lock->unlock();
468
469 }
470 #if INCLUDE_ALL_GCS
471 // If there are any concurrent GC threads resume them.
472 if (UseConcMarkSweepGC) {
473 ConcurrentMarkSweepThread::desynchronize(false);
474 } else if (UseG1GC) {
475 SuspendibleThreadSet::desynchronize();
476 } else if (UseShenandoahGC) {
477 ShenandoahConcurrentThread::safepoint_desynchronize();
478 }
479 #endif // INCLUDE_ALL_GCS
480 // record this time so VMThread can keep track how much time has elapsed
481 // since last safepoint.
482 _end_of_last_safepoint = os::javaTimeMillis();
483 }
484
485 bool SafepointSynchronize::is_cleanup_needed() {
486 // Need a safepoint if some inline cache buffers is non-empty
487 if (!InlineCacheBuffer::is_empty()) return true;
488 return false;
489 }
490
491
492
493 // Various cleaning tasks that should be done periodically at safepoints
494 void SafepointSynchronize::do_cleanup_tasks() {
495 {
496 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime);
497 ObjectSynchronizer::deflate_idle_monitors();
498 }
499
500 {
501 TraceTime t2("updating inline caches", TraceSafepointCleanupTime);
502 InlineCacheBuffer::update_inline_caches();
503 }
504 {
505 TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime);
506 CompilationPolicy::policy()->do_safepoint_work();
507 }
508
509 {
510 TraceTime t4("mark nmethods", TraceSafepointCleanupTime);
511 NMethodSweeper::mark_active_nmethods();
512 }
513
514 if (SymbolTable::needs_rehashing()) {
515 TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime);
516 SymbolTable::rehash_table();
517 }
518
519 if (StringTable::needs_rehashing()) {
520 TraceTime t6("rehashing string table", TraceSafepointCleanupTime);
521 StringTable::rehash_table();
522 }
523
524 // rotate log files?
525 if (UseGCLogFileRotation) {
526 gclog_or_tty->rotate_log(false);
527 }
528
529 {
530 // CMS delays purging the CLDG until the beginning of the next safepoint and to
531 // make sure concurrent sweep is done
532 TraceTime t7("purging class loader data graph", TraceSafepointCleanupTime);
533 ClassLoaderDataGraph::purge_if_needed();
534 }
535 }
536
537
538 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
539 switch(state) {
540 case _thread_in_native:
541 // native threads are safe if they have no java stack or have walkable stack
542 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
543
544 // blocked threads should have already have walkable stack
545 case _thread_blocked:
546 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
547 return true;
548
549 default:
550 return false;
551 }
552 }
553
554
555 // See if the thread is running inside a lazy critical native and
556 // update the thread critical count if so. Also set a suspend flag to
557 // cause the native wrapper to return into the JVM to do the unlock
558 // once the native finishes.
559 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
560 if (state == _thread_in_native &&
561 thread->has_last_Java_frame() &&
562 thread->frame_anchor()->walkable()) {
563 // This thread might be in a critical native nmethod so look at
564 // the top of the stack and increment the critical count if it
565 // is.
566 frame wrapper_frame = thread->last_frame();
567 CodeBlob* stub_cb = wrapper_frame.cb();
568 if (stub_cb != NULL &&
569 stub_cb->is_nmethod() &&
570 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
571 // A thread could potentially be in a critical native across
572 // more than one safepoint, so only update the critical state on
573 // the first one. When it returns it will perform the unlock.
574 if (!thread->do_critical_native_unlock()) {
575 #ifdef ASSERT
576 if (!thread->in_critical()) {
577 GC_locker::increment_debug_jni_lock_count();
578 }
579 #endif
580 thread->enter_critical();
581 // Make sure the native wrapper calls back on return to
582 // perform the needed critical unlock.
583 thread->set_critical_native_unlock();
584 }
585 }
586 }
587 }
588
589
590
591 // -------------------------------------------------------------------------------------------------------
592 // Implementation of Safepoint callback point
593
594 void SafepointSynchronize::block(JavaThread *thread) {
595 assert(thread != NULL, "thread must be set");
596 assert(thread->is_Java_thread(), "not a Java thread");
597
598 // Threads shouldn't block if they are in the middle of printing, but...
599 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
600
601 // Only bail from the block() call if the thread is gone from the
602 // thread list; starting to exit should still block.
603 if (thread->is_terminated()) {
604 // block current thread if we come here from native code when VM is gone
605 thread->block_if_vm_exited();
606
607 // otherwise do nothing
608 return;
609 }
610
611 JavaThreadState state = thread->thread_state();
612 thread->frame_anchor()->make_walkable(thread);
613
614 // Check that we have a valid thread_state at this point
615 switch(state) {
616 case _thread_in_vm_trans:
617 case _thread_in_Java: // From compiled code
618
619 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
620 // we pretend we are still in the VM.
621 thread->set_thread_state(_thread_in_vm);
622
623 if (is_synchronizing()) {
624 Atomic::inc (&TryingToBlock) ;
625 }
626
627 // We will always be holding the Safepoint_lock when we are examine the state
628 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
629 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
630 Safepoint_lock->lock_without_safepoint_check();
631 if (is_synchronizing()) {
632 // Decrement the number of threads to wait for and signal vm thread
633 assert(_waiting_to_block > 0, "sanity check");
634 _waiting_to_block--;
635 thread->safepoint_state()->set_has_called_back(true);
636
637 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
638 if (thread->in_critical()) {
639 // Notice that this thread is in a critical section
640 increment_jni_active_count();
641 }
642
643 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
644 if (_waiting_to_block == 0) {
645 Safepoint_lock->notify_all();
646 }
647 }
648
649 // We transition the thread to state _thread_blocked here, but
650 // we can't do our usual check for external suspension and then
651 // self-suspend after the lock_without_safepoint_check() call
652 // below because we are often called during transitions while
653 // we hold different locks. That would leave us suspended while
654 // holding a resource which results in deadlocks.
655 thread->set_thread_state(_thread_blocked);
656 Safepoint_lock->unlock();
657
658 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
659 // the entire safepoint, the threads will all line up here during the safepoint.
660 Threads_lock->lock_without_safepoint_check();
661 // restore original state. This is important if the thread comes from compiled code, so it
662 // will continue to execute with the _thread_in_Java state.
663 thread->set_thread_state(state);
664 Threads_lock->unlock();
665 break;
666
667 case _thread_in_native_trans:
668 case _thread_blocked_trans:
669 case _thread_new_trans:
670 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
671 thread->print_thread_state();
672 fatal("Deadlock in safepoint code. "
673 "Should have called back to the VM before blocking.");
674 }
675
676 // We transition the thread to state _thread_blocked here, but
677 // we can't do our usual check for external suspension and then
678 // self-suspend after the lock_without_safepoint_check() call
679 // below because we are often called during transitions while
680 // we hold different locks. That would leave us suspended while
681 // holding a resource which results in deadlocks.
682 thread->set_thread_state(_thread_blocked);
683
684 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
685 // the safepoint code might still be waiting for it to block. We need to change the state here,
686 // so it can see that it is at a safepoint.
687
688 // Block until the safepoint operation is completed.
689 Threads_lock->lock_without_safepoint_check();
690
691 // Restore state
692 thread->set_thread_state(state);
693
694 Threads_lock->unlock();
695 break;
696
697 default:
698 fatal(err_msg("Illegal threadstate encountered: %d", state));
699 }
700
701 // Check for pending. async. exceptions or suspends - except if the
702 // thread was blocked inside the VM. has_special_runtime_exit_condition()
703 // is called last since it grabs a lock and we only want to do that when
704 // we must.
705 //
706 // Note: we never deliver an async exception at a polling point as the
707 // compiler may not have an exception handler for it. The polling
708 // code will notice the async and deoptimize and the exception will
709 // be delivered. (Polling at a return point is ok though). Sure is
710 // a lot of bother for a deprecated feature...
711 //
712 // We don't deliver an async exception if the thread state is
713 // _thread_in_native_trans so JNI functions won't be called with
714 // a surprising pending exception. If the thread state is going back to java,
715 // async exception is checked in check_special_condition_for_native_trans().
716
717 if (state != _thread_blocked_trans &&
718 state != _thread_in_vm_trans &&
719 thread->has_special_runtime_exit_condition()) {
720 thread->handle_special_runtime_exit_condition(
721 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
722 }
723 }
724
725 // ------------------------------------------------------------------------------------------------------
726 // Exception handlers
727
728
729 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
730 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
731 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
732 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
733
734 if (ShowSafepointMsgs) {
735 tty->print("handle_polling_page_exception: ");
736 }
737
738 if (PrintSafepointStatistics) {
739 inc_page_trap_count();
740 }
741
742 ThreadSafepointState* state = thread->safepoint_state();
743
744 state->handle_polling_page_exception();
745 }
746
747
748 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
749 if (!timeout_error_printed) {
750 timeout_error_printed = true;
751 // Print out the thread info which didn't reach the safepoint for debugging
752 // purposes (useful when there are lots of threads in the debugger).
753 tty->cr();
754 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
755 if (reason == _spinning_timeout) {
756 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
757 } else if (reason == _blocking_timeout) {
758 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
759 }
760
761 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
762 ThreadSafepointState *cur_state;
763 ResourceMark rm;
764 for(JavaThread *cur_thread = Threads::first(); cur_thread;
765 cur_thread = cur_thread->next()) {
766 cur_state = cur_thread->safepoint_state();
767
768 if (cur_thread->thread_state() != _thread_blocked &&
769 ((reason == _spinning_timeout && cur_state->is_running()) ||
770 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
771 tty->print("# ");
772 cur_thread->print();
773 tty->cr();
774 }
775 }
776 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
777 }
778
779 // To debug the long safepoint, specify both DieOnSafepointTimeout &
780 // ShowMessageBoxOnError.
781 if (DieOnSafepointTimeout) {
782 char msg[1024];
783 VM_Operation *op = VMThread::vm_operation();
784 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
785 SafepointTimeoutDelay,
786 op != NULL ? op->name() : "no vm operation");
787 fatal(msg);
788 }
789 }
790
791
792 // -------------------------------------------------------------------------------------------------------
793 // Implementation of ThreadSafepointState
794
795 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
796 _thread = thread;
797 _type = _running;
798 _has_called_back = false;
799 _at_poll_safepoint = false;
800 }
801
802 void ThreadSafepointState::create(JavaThread *thread) {
803 ThreadSafepointState *state = new ThreadSafepointState(thread);
804 thread->set_safepoint_state(state);
805 }
806
807 void ThreadSafepointState::destroy(JavaThread *thread) {
808 if (thread->safepoint_state()) {
809 delete(thread->safepoint_state());
810 thread->set_safepoint_state(NULL);
811 }
812 }
813
814 void ThreadSafepointState::examine_state_of_thread() {
815 assert(is_running(), "better be running or just have hit safepoint poll");
816
817 JavaThreadState state = _thread->thread_state();
818
819 // Save the state at the start of safepoint processing.
820 _orig_thread_state = state;
821
822 // Check for a thread that is suspended. Note that thread resume tries
823 // to grab the Threads_lock which we own here, so a thread cannot be
824 // resumed during safepoint synchronization.
825
826 // We check to see if this thread is suspended without locking to
827 // avoid deadlocking with a third thread that is waiting for this
828 // thread to be suspended. The third thread can notice the safepoint
829 // that we're trying to start at the beginning of its SR_lock->wait()
830 // call. If that happens, then the third thread will block on the
831 // safepoint while still holding the underlying SR_lock. We won't be
832 // able to get the SR_lock and we'll deadlock.
833 //
834 // We don't need to grab the SR_lock here for two reasons:
835 // 1) The suspend flags are both volatile and are set with an
836 // Atomic::cmpxchg() call so we should see the suspended
837 // state right away.
838 // 2) We're being called from the safepoint polling loop; if
839 // we don't see the suspended state on this iteration, then
840 // we'll come around again.
841 //
842 bool is_suspended = _thread->is_ext_suspended();
843 if (is_suspended) {
844 roll_forward(_at_safepoint);
845 return;
846 }
847
848 // Some JavaThread states have an initial safepoint state of
849 // running, but are actually at a safepoint. We will happily
850 // agree and update the safepoint state here.
851 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
852 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
853 roll_forward(_at_safepoint);
854 return;
855 }
856
857 if (state == _thread_in_vm) {
858 roll_forward(_call_back);
859 return;
860 }
861
862 // All other thread states will continue to run until they
863 // transition and self-block in state _blocked
864 // Safepoint polling in compiled code causes the Java threads to do the same.
865 // Note: new threads may require a malloc so they must be allowed to finish
866
867 assert(is_running(), "examine_state_of_thread on non-running thread");
868 return;
869 }
870
871 // Returns true is thread could not be rolled forward at present position.
872 void ThreadSafepointState::roll_forward(suspend_type type) {
873 _type = type;
874
875 switch(_type) {
876 case _at_safepoint:
877 SafepointSynchronize::signal_thread_at_safepoint();
878 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
879 if (_thread->in_critical()) {
880 // Notice that this thread is in a critical section
881 SafepointSynchronize::increment_jni_active_count();
882 }
883 break;
884
885 case _call_back:
886 set_has_called_back(false);
887 break;
888
889 case _running:
890 default:
891 ShouldNotReachHere();
892 }
893 }
894
895 void ThreadSafepointState::restart() {
896 switch(type()) {
897 case _at_safepoint:
898 case _call_back:
899 break;
900
901 case _running:
902 default:
903 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
904 _thread, _type);
905 _thread->print();
906 ShouldNotReachHere();
907 }
908 _type = _running;
909 set_has_called_back(false);
910 }
911
912
913 void ThreadSafepointState::print_on(outputStream *st) const {
914 const char *s;
915
916 switch(_type) {
917 case _running : s = "_running"; break;
918 case _at_safepoint : s = "_at_safepoint"; break;
919 case _call_back : s = "_call_back"; break;
920 default:
921 ShouldNotReachHere();
922 }
923
924 st->print_cr("Thread: " INTPTR_FORMAT
925 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
926 _thread, _thread->osthread()->thread_id(), s, _has_called_back,
927 _at_poll_safepoint);
928
929 _thread->print_thread_state_on(st);
930 }
931
932
933 // ---------------------------------------------------------------------------------------------------------------------
934
935 // Block the thread at the safepoint poll or poll return.
936 void ThreadSafepointState::handle_polling_page_exception() {
937
938 // Check state. block() will set thread state to thread_in_vm which will
939 // cause the safepoint state _type to become _call_back.
940 assert(type() == ThreadSafepointState::_running,
941 "polling page exception on thread not running state");
942
943 // Step 1: Find the nmethod from the return address
944 if (ShowSafepointMsgs && Verbose) {
945 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
946 }
947 address real_return_addr = thread()->saved_exception_pc();
948
949 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
950 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
951 nmethod* nm = (nmethod*)cb;
952
953 // Find frame of caller
954 frame stub_fr = thread()->last_frame();
955 CodeBlob* stub_cb = stub_fr.cb();
956 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
957 RegisterMap map(thread(), true);
958 frame caller_fr = stub_fr.sender(&map);
959
960 // Should only be poll_return or poll
961 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
962
963 // This is a poll immediately before a return. The exception handling code
964 // has already had the effect of causing the return to occur, so the execution
965 // will continue immediately after the call. In addition, the oopmap at the
966 // return point does not mark the return value as an oop (if it is), so
967 // it needs a handle here to be updated.
968 if( nm->is_at_poll_return(real_return_addr) ) {
969 // See if return type is an oop.
970 bool return_oop = nm->method()->is_returning_oop();
971 Handle return_value;
972 if (return_oop) {
973 // The oop result has been saved on the stack together with all
974 // the other registers. In order to preserve it over GCs we need
975 // to keep it in a handle.
976 oop result = caller_fr.saved_oop_result(&map);
977 if (ShenandoahVerifyReadsToFromSpace) {
978 result = oopDesc::bs()->read_barrier(result);
979 }
980 assert(result == NULL || result->is_oop(), "must be oop");
981 return_value = Handle(thread(), result);
982 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
983 }
984
985 // Block the thread
986 SafepointSynchronize::block(thread());
987
988 // restore oop result, if any
989 if (return_oop) {
990 caller_fr.set_saved_oop_result(&map, return_value());
991 }
992 }
993
994 // This is a safepoint poll. Verify the return address and block.
995 else {
996 set_at_poll_safepoint(true);
997
998 // verify the blob built the "return address" correctly
999 assert(real_return_addr == caller_fr.pc(), "must match");
1000
1001 // Block the thread
1002 SafepointSynchronize::block(thread());
1003 set_at_poll_safepoint(false);
1004
1005 // If we have a pending async exception deoptimize the frame
1006 // as otherwise we may never deliver it.
1007 if (thread()->has_async_condition()) {
1008 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1009 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1010 }
1011
1012 // If an exception has been installed we must check for a pending deoptimization
1013 // Deoptimize frame if exception has been thrown.
1014
1015 if (thread()->has_pending_exception() ) {
1016 RegisterMap map(thread(), true);
1017 frame caller_fr = stub_fr.sender(&map);
1018 if (caller_fr.is_deoptimized_frame()) {
1019 // The exception patch will destroy registers that are still
1020 // live and will be needed during deoptimization. Defer the
1021 // Async exception should have deferred the exception until the
1022 // next safepoint which will be detected when we get into
1023 // the interpreter so if we have an exception now things
1024 // are messed up.
1025
1026 fatal("Exception installed and deoptimization is pending");
1027 }
1028 }
1029 }
1030 }
1031
1032
1033 //
1034 // Statistics & Instrumentations
1035 //
1036 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1037 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1038 int SafepointSynchronize::_cur_stat_index = 0;
1039 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1040 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1041 jlong SafepointSynchronize::_max_sync_time = 0;
1042 jlong SafepointSynchronize::_max_vmop_time = 0;
1043 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1044
1045 static jlong cleanup_end_time = 0;
1046 static bool need_to_track_page_armed_status = false;
1047 static bool init_done = false;
1048
1049 // Helper method to print the header.
1050 static void print_header() {
1051 tty->print(" vmop "
1052 "[threads: total initially_running wait_to_block] ");
1053 tty->print("[time: spin block sync cleanup vmop] ");
1054
1055 // no page armed status printed out if it is always armed.
1056 if (need_to_track_page_armed_status) {
1057 tty->print("page_armed ");
1058 }
1059
1060 tty->print_cr("page_trap_count");
1061 }
1062
1063 void SafepointSynchronize::deferred_initialize_stat() {
1064 if (init_done) return;
1065
1066 if (PrintSafepointStatisticsCount <= 0) {
1067 fatal("Wrong PrintSafepointStatisticsCount");
1068 }
1069
1070 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1071 // be printed right away, in which case, _safepoint_stats will regress to
1072 // a single element array. Otherwise, it is a circular ring buffer with default
1073 // size of PrintSafepointStatisticsCount.
1074 int stats_array_size;
1075 if (PrintSafepointStatisticsTimeout > 0) {
1076 stats_array_size = 1;
1077 PrintSafepointStatistics = true;
1078 } else {
1079 stats_array_size = PrintSafepointStatisticsCount;
1080 }
1081 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1082 * sizeof(SafepointStats), mtInternal);
1083 guarantee(_safepoint_stats != NULL,
1084 "not enough memory for safepoint instrumentation data");
1085
1086 if (DeferPollingPageLoopCount >= 0) {
1087 need_to_track_page_armed_status = true;
1088 }
1089 init_done = true;
1090 }
1091
1092 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1093 assert(init_done, "safepoint statistics array hasn't been initialized");
1094 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1095
1096 spstat->_time_stamp = _ts_of_current_safepoint;
1097
1098 VM_Operation *op = VMThread::vm_operation();
1099 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1100 if (op != NULL) {
1101 _safepoint_reasons[spstat->_vmop_type]++;
1102 }
1103
1104 spstat->_nof_total_threads = nof_threads;
1105 spstat->_nof_initial_running_threads = nof_running;
1106 spstat->_nof_threads_hit_page_trap = 0;
1107
1108 // Records the start time of spinning. The real time spent on spinning
1109 // will be adjusted when spin is done. Same trick is applied for time
1110 // spent on waiting for threads to block.
1111 if (nof_running != 0) {
1112 spstat->_time_to_spin = os::javaTimeNanos();
1113 } else {
1114 spstat->_time_to_spin = 0;
1115 }
1116 }
1117
1118 void SafepointSynchronize::update_statistics_on_spin_end() {
1119 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1120
1121 jlong cur_time = os::javaTimeNanos();
1122
1123 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1124 if (spstat->_nof_initial_running_threads != 0) {
1125 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1126 }
1127
1128 if (need_to_track_page_armed_status) {
1129 spstat->_page_armed = (PageArmed == 1);
1130 }
1131
1132 // Records the start time of waiting for to block. Updated when block is done.
1133 if (_waiting_to_block != 0) {
1134 spstat->_time_to_wait_to_block = cur_time;
1135 } else {
1136 spstat->_time_to_wait_to_block = 0;
1137 }
1138 }
1139
1140 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1141 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1142
1143 if (spstat->_nof_threads_wait_to_block != 0) {
1144 spstat->_time_to_wait_to_block = end_time -
1145 spstat->_time_to_wait_to_block;
1146 }
1147
1148 // Records the end time of sync which will be used to calculate the total
1149 // vm operation time. Again, the real time spending in syncing will be deducted
1150 // from the start of the sync time later when end_statistics is called.
1151 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1152 if (spstat->_time_to_sync > _max_sync_time) {
1153 _max_sync_time = spstat->_time_to_sync;
1154 }
1155
1156 spstat->_time_to_do_cleanups = end_time;
1157 }
1158
1159 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1160 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1161
1162 // Record how long spent in cleanup tasks.
1163 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1164
1165 cleanup_end_time = end_time;
1166 }
1167
1168 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1169 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1170
1171 // Update the vm operation time.
1172 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1173 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1174 _max_vmop_time = spstat->_time_to_exec_vmop;
1175 }
1176 // Only the sync time longer than the specified
1177 // PrintSafepointStatisticsTimeout will be printed out right away.
1178 // By default, it is -1 meaning all samples will be put into the list.
1179 if ( PrintSafepointStatisticsTimeout > 0) {
1180 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1181 print_statistics();
1182 }
1183 } else {
1184 // The safepoint statistics will be printed out when the _safepoin_stats
1185 // array fills up.
1186 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1187 print_statistics();
1188 _cur_stat_index = 0;
1189 } else {
1190 _cur_stat_index++;
1191 }
1192 }
1193 }
1194
1195 void SafepointSynchronize::print_statistics() {
1196 SafepointStats* sstats = _safepoint_stats;
1197
1198 for (int index = 0; index <= _cur_stat_index; index++) {
1199 if (index % 30 == 0) {
1200 print_header();
1201 }
1202 sstats = &_safepoint_stats[index];
1203 tty->print("%.3f: ", sstats->_time_stamp);
1204 tty->print("%-26s ["
1205 INT32_FORMAT_W(8) INT32_FORMAT_W(11) INT32_FORMAT_W(15)
1206 " ] ",
1207 sstats->_vmop_type == -1 ? "no vm operation" :
1208 VM_Operation::name(sstats->_vmop_type),
1209 sstats->_nof_total_threads,
1210 sstats->_nof_initial_running_threads,
1211 sstats->_nof_threads_wait_to_block);
1212 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1213 tty->print(" ["
1214 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1215 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1216 INT64_FORMAT_W(6) " ] ",
1217 sstats->_time_to_spin / MICROUNITS,
1218 sstats->_time_to_wait_to_block / MICROUNITS,
1219 sstats->_time_to_sync / MICROUNITS,
1220 sstats->_time_to_do_cleanups / MICROUNITS,
1221 sstats->_time_to_exec_vmop / MICROUNITS);
1222
1223 if (need_to_track_page_armed_status) {
1224 tty->print(INT32_FORMAT " ", sstats->_page_armed);
1225 }
1226 tty->print_cr(INT32_FORMAT " ", sstats->_nof_threads_hit_page_trap);
1227 }
1228 }
1229
1230 // This method will be called when VM exits. It will first call
1231 // print_statistics to print out the rest of the sampling. Then
1232 // it tries to summarize the sampling.
1233 void SafepointSynchronize::print_stat_on_exit() {
1234 if (_safepoint_stats == NULL) return;
1235
1236 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1237
1238 // During VM exit, end_statistics may not get called and in that
1239 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1240 // don't print it out.
1241 // Approximate the vm op time.
1242 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1243 os::javaTimeNanos() - cleanup_end_time;
1244
1245 if ( PrintSafepointStatisticsTimeout < 0 ||
1246 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1247 print_statistics();
1248 }
1249 tty->cr();
1250
1251 // Print out polling page sampling status.
1252 if (!need_to_track_page_armed_status) {
1253 tty->print_cr("Polling page always armed");
1254 } else {
1255 tty->print_cr("Defer polling page loop count = %d\n",
1256 DeferPollingPageLoopCount);
1257 }
1258
1259 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1260 if (_safepoint_reasons[index] != 0) {
1261 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1262 _safepoint_reasons[index]);
1263 }
1264 }
1265
1266 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1267 _coalesced_vmop_count);
1268 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1269 _max_sync_time / MICROUNITS);
1270 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1271 INT64_FORMAT_W(5) " ms",
1272 _max_vmop_time / MICROUNITS);
1273 }
1274
1275 // ------------------------------------------------------------------------------------------------
1276 // Non-product code
1277
1278 #ifndef PRODUCT
1279
1280 void SafepointSynchronize::print_state() {
1281 if (_state == _not_synchronized) {
1282 tty->print_cr("not synchronized");
1283 } else if (_state == _synchronizing || _state == _synchronized) {
1284 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1285 "synchronized");
1286
1287 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1288 cur->safepoint_state()->print();
1289 }
1290 }
1291 }
1292
1293 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1294 if (ShowSafepointMsgs) {
1295 va_list ap;
1296 va_start(ap, format);
1297 tty->vprint_cr(format, ap);
1298 va_end(ap);
1299 }
1300 }
1301
1302 #endif // !PRODUCT