1 /*
2 * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/stringTable.hpp"
27 #include "classfile/symbolTable.hpp"
28 #include "classfile/systemDictionary.hpp"
29 #include "code/codeCache.hpp"
30 #include "code/icBuffer.hpp"
31 #include "code/nmethod.hpp"
32 #include "code/pcDesc.hpp"
33 #include "code/scopeDesc.hpp"
34 #include "gc/shared/collectedHeap.hpp"
35 #include "gc/shared/gcLocker.inline.hpp"
36 #include "interpreter/interpreter.hpp"
37 #include "logging/log.hpp"
38 #include "memory/resourceArea.hpp"
39 #include "memory/universe.inline.hpp"
40 #include "oops/oop.inline.hpp"
41 #include "oops/symbol.hpp"
42 #include "runtime/atomic.hpp"
43 #include "runtime/compilationPolicy.hpp"
44 #include "runtime/deoptimization.hpp"
45 #include "runtime/frame.inline.hpp"
46 #include "runtime/interfaceSupport.hpp"
47 #include "runtime/mutexLocker.hpp"
48 #include "runtime/orderAccess.inline.hpp"
49 #include "runtime/osThread.hpp"
50 #include "runtime/safepoint.hpp"
51 #include "runtime/signature.hpp"
52 #include "runtime/stubCodeGenerator.hpp"
53 #include "runtime/stubRoutines.hpp"
54 #include "runtime/sweeper.hpp"
55 #include "runtime/synchronizer.hpp"
56 #include "runtime/thread.inline.hpp"
57 #include "runtime/timerTrace.hpp"
58 #include "services/runtimeService.hpp"
59 #include "trace/tracing.hpp"
60 #include "trace/traceMacros.hpp"
61 #include "utilities/events.hpp"
62 #include "utilities/macros.hpp"
63 #if INCLUDE_ALL_GCS
64 #include "gc/cms/concurrentMarkSweepThread.hpp"
65 #include "gc/g1/suspendibleThreadSet.hpp"
66 #endif // INCLUDE_ALL_GCS
67 #ifdef COMPILER1
68 #include "c1/c1_globals.hpp"
69 #endif
70
71 // --------------------------------------------------------------------------------------------------
72 // Implementation of Safepoint begin/end
73
74 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
75 volatile int SafepointSynchronize::_waiting_to_block = 0;
76 volatile int SafepointSynchronize::_safepoint_counter = 0;
77 int SafepointSynchronize::_current_jni_active_count = 0;
78 long SafepointSynchronize::_end_of_last_safepoint = 0;
79 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
80 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
81 static bool timeout_error_printed = false;
82
83 // Roll all threads forward to a safepoint and suspend them all
84 void SafepointSynchronize::begin() {
85 EventSafepointBegin begin_event;
86 Thread* myThread = Thread::current();
87 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
88
89 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
90 _safepoint_begin_time = os::javaTimeNanos();
91 _ts_of_current_safepoint = tty->time_stamp().seconds();
92 }
93
94 #if INCLUDE_ALL_GCS
95 if (UseConcMarkSweepGC) {
96 // In the future we should investigate whether CMS can use the
97 // more-general mechanism below. DLD (01/05).
98 ConcurrentMarkSweepThread::synchronize(false);
99 } else if (UseG1GC) {
100 SuspendibleThreadSet::synchronize();
101 }
102 #endif // INCLUDE_ALL_GCS
103
104 // By getting the Threads_lock, we assure that no threads are about to start or
105 // exit. It is released again in SafepointSynchronize::end().
106 Threads_lock->lock();
107
108 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
109
110 int nof_threads = Threads::number_of_threads();
111
112 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads);
113
114 RuntimeService::record_safepoint_begin();
115
116 MutexLocker mu(Safepoint_lock);
117
118 // Reset the count of active JNI critical threads
119 _current_jni_active_count = 0;
120
121 // Set number of threads to wait for, before we initiate the callbacks
122 _waiting_to_block = nof_threads;
123 TryingToBlock = 0 ;
124 int still_running = nof_threads;
125
126 // Save the starting time, so that it can be compared to see if this has taken
127 // too long to complete.
128 jlong safepoint_limit_time = 0;
129 timeout_error_printed = false;
130
131 // PrintSafepointStatisticsTimeout can be specified separately. When
132 // specified, PrintSafepointStatistics will be set to true in
133 // deferred_initialize_stat method. The initialization has to be done
134 // early enough to avoid any races. See bug 6880029 for details.
135 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
136 deferred_initialize_stat();
137 }
138
139 // Begin the process of bringing the system to a safepoint.
140 // Java threads can be in several different states and are
141 // stopped by different mechanisms:
142 //
143 // 1. Running interpreted
144 // The interpreter dispatch table is changed to force it to
145 // check for a safepoint condition between bytecodes.
146 // 2. Running in native code
147 // When returning from the native code, a Java thread must check
148 // the safepoint _state to see if we must block. If the
149 // VM thread sees a Java thread in native, it does
150 // not wait for this thread to block. The order of the memory
151 // writes and reads of both the safepoint state and the Java
152 // threads state is critical. In order to guarantee that the
153 // memory writes are serialized with respect to each other,
154 // the VM thread issues a memory barrier instruction
155 // (on MP systems). In order to avoid the overhead of issuing
156 // a memory barrier for each Java thread making native calls, each Java
157 // thread performs a write to a single memory page after changing
158 // the thread state. The VM thread performs a sequence of
159 // mprotect OS calls which forces all previous writes from all
160 // Java threads to be serialized. This is done in the
161 // os::serialize_thread_states() call. This has proven to be
162 // much more efficient than executing a membar instruction
163 // on every call to native code.
164 // 3. Running compiled Code
165 // Compiled code reads a global (Safepoint Polling) page that
166 // is set to fault if we are trying to get to a safepoint.
167 // 4. Blocked
168 // A thread which is blocked will not be allowed to return from the
169 // block condition until the safepoint operation is complete.
170 // 5. In VM or Transitioning between states
171 // If a Java thread is currently running in the VM or transitioning
172 // between states, the safepointing code will wait for the thread to
173 // block itself when it attempts transitions to a new state.
174 //
175 {
176 EventSafepointStateSynchronization sync_event;
177 int initial_running = 0;
178
179 _state = _synchronizing;
180 OrderAccess::fence();
181
182 // Flush all thread states to memory
183 if (!UseMembar) {
184 os::serialize_thread_states();
185 }
186
187 // Make interpreter safepoint aware
188 Interpreter::notice_safepoints();
189
190 if (DeferPollingPageLoopCount < 0) {
191 // Make polling safepoint aware
192 guarantee (PageArmed == 0, "invariant") ;
193 PageArmed = 1 ;
194 os::make_polling_page_unreadable();
195 }
196
197 // Consider using active_processor_count() ... but that call is expensive.
198 int ncpus = os::processor_count() ;
199
200 #ifdef ASSERT
201 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
202 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
203 // Clear the visited flag to ensure that the critical counts are collected properly.
204 cur->set_visited_for_critical_count(false);
205 }
206 #endif // ASSERT
207
208 if (SafepointTimeout)
209 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
210
211 // Iterate through all threads until it have been determined how to stop them all at a safepoint
212 unsigned int iterations = 0;
213 int steps = 0 ;
214 while(still_running > 0) {
215 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
216 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
217 ThreadSafepointState *cur_state = cur->safepoint_state();
218 if (cur_state->is_running()) {
219 cur_state->examine_state_of_thread();
220 if (!cur_state->is_running()) {
221 still_running--;
222 // consider adjusting steps downward:
223 // steps = 0
224 // steps -= NNN
225 // steps >>= 1
226 // steps = MIN(steps, 2000-100)
227 // if (iterations != 0) steps -= NNN
228 }
229 if (log_is_enabled(Trace, safepoint)) {
230 ResourceMark rm;
231 cur_state->print_on(Log(safepoint)::trace_stream());
232 }
233 }
234 }
235
236 if (iterations == 0) {
237 initial_running = still_running;
238 if (PrintSafepointStatistics) {
239 begin_statistics(nof_threads, still_running);
240 }
241 }
242
243 if (still_running > 0) {
244 // Check for if it takes to long
245 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
246 print_safepoint_timeout(_spinning_timeout);
247 }
248
249 // Spin to avoid context switching.
250 // There's a tension between allowing the mutators to run (and rendezvous)
251 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
252 // a mutator might otherwise use profitably to reach a safepoint. Excessive
253 // spinning by the VM thread on a saturated system can increase rendezvous latency.
254 // Blocking or yielding incur their own penalties in the form of context switching
255 // and the resultant loss of $ residency.
256 //
257 // Further complicating matters is that yield() does not work as naively expected
258 // on many platforms -- yield() does not guarantee that any other ready threads
259 // will run. As such we revert to naked_short_sleep() after some number of iterations.
260 // nakes_short_sleep() is implemented as a short unconditional sleep.
261 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
262 // can actually increase the time it takes the VM thread to detect that a system-wide
263 // stop-the-world safepoint has been reached. In a pathological scenario such as that
264 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
265 // In that case the mutators will be stalled waiting for the safepoint to complete and the
266 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
267 // will eventually wake up and detect that all mutators are safe, at which point
268 // we'll again make progress.
269 //
270 // Beware too that that the VMThread typically runs at elevated priority.
271 // Its default priority is higher than the default mutator priority.
272 // Obviously, this complicates spinning.
273 //
274 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
275 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
276 //
277 // See the comments in synchronizer.cpp for additional remarks on spinning.
278 //
279 // In the future we might:
280 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
281 // This is tricky as the path used by a thread exiting the JVM (say on
282 // on JNI call-out) simply stores into its state field. The burden
283 // is placed on the VM thread, which must poll (spin).
284 // 2. Find something useful to do while spinning. If the safepoint is GC-related
285 // we might aggressively scan the stacks of threads that are already safe.
286 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
287 // If all the mutators are ONPROC there's no reason to sleep or yield.
288 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
289 // 5. Check system saturation. If the system is not fully saturated then
290 // simply spin and avoid sleep/yield.
291 // 6. As still-running mutators rendezvous they could unpark the sleeping
292 // VMthread. This works well for still-running mutators that become
293 // safe. The VMthread must still poll for mutators that call-out.
294 // 7. Drive the policy on time-since-begin instead of iterations.
295 // 8. Consider making the spin duration a function of the # of CPUs:
296 // Spin = (((ncpus-1) * M) + K) + F(still_running)
297 // Alternately, instead of counting iterations of the outer loop
298 // we could count the # of threads visited in the inner loop, above.
299 // 9. On windows consider using the return value from SwitchThreadTo()
300 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
301
302 if (int(iterations) == DeferPollingPageLoopCount) {
303 guarantee (PageArmed == 0, "invariant") ;
304 PageArmed = 1 ;
305 os::make_polling_page_unreadable();
306 }
307
308 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
309 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
310 ++steps ;
311 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
312 SpinPause() ; // MP-Polite spin
313 } else
314 if (steps < DeferThrSuspendLoopCount) {
315 os::naked_yield() ;
316 } else {
317 os::naked_short_sleep(1);
318 }
319
320 iterations ++ ;
321 }
322 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
323 }
324 assert(still_running == 0, "sanity check");
325
326 if (PrintSafepointStatistics) {
327 update_statistics_on_spin_end();
328 }
329
330 if (sync_event.should_commit()) {
331 sync_event.set_safepointId(safepoint_counter());
332 sync_event.set_initialThreadCount(initial_running);
333 sync_event.set_runningThreadCount(_waiting_to_block);
334 sync_event.set_iterations(iterations);
335 sync_event.commit();
336 }
337 } //EventSafepointStateSync
338
339 // wait until all threads are stopped
340 {
341 EventSafepointWaitBlocked wait_blocked_event;
342 int initial_waiting_to_block = _waiting_to_block;
343
344 while (_waiting_to_block > 0) {
345 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
346 if (!SafepointTimeout || timeout_error_printed) {
347 Safepoint_lock->wait(true); // true, means with no safepoint checks
348 } else {
349 // Compute remaining time
350 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
351
352 // If there is no remaining time, then there is an error
353 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
354 print_safepoint_timeout(_blocking_timeout);
355 }
356 }
357 }
358 assert(_waiting_to_block == 0, "sanity check");
359
360 #ifndef PRODUCT
361 if (SafepointTimeout) {
362 jlong current_time = os::javaTimeNanos();
363 if (safepoint_limit_time < current_time) {
364 tty->print_cr("# SafepointSynchronize: Finished after "
365 INT64_FORMAT_W(6) " ms",
366 ((current_time - safepoint_limit_time) / MICROUNITS +
367 (jlong)SafepointTimeoutDelay));
368 }
369 }
370 #endif
371
372 assert((_safepoint_counter & 0x1) == 0, "must be even");
373 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
374 _safepoint_counter ++;
375
376 // Record state
377 _state = _synchronized;
378
379 OrderAccess::fence();
380
381 if (wait_blocked_event.should_commit()) {
382 wait_blocked_event.set_safepointId(safepoint_counter());
383 wait_blocked_event.set_runningThreadCount(initial_waiting_to_block);
384 wait_blocked_event.commit();
385 }
386 } // EventSafepointWaitBlocked
387
388 #ifdef ASSERT
389 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
390 // make sure all the threads were visited
391 assert(cur->was_visited_for_critical_count(), "missed a thread");
392 }
393 #endif // ASSERT
394
395 // Update the count of active JNI critical regions
396 GCLocker::set_jni_lock_count(_current_jni_active_count);
397
398 if (log_is_enabled(Debug, safepoint)) {
399 log_debug(safepoint)("Entering safepoint region: %s", VMThread::vm_safepoint_description());
400 }
401
402 RuntimeService::record_safepoint_synchronized();
403 if (PrintSafepointStatistics) {
404 update_statistics_on_sync_end(os::javaTimeNanos());
405 }
406
407 // Call stuff that needs to be run when a safepoint is just about to be completed
408 {
409 EventSafepointCleanup cleanup_event;
410 do_cleanup_tasks();
411 if (cleanup_event.should_commit()) {
412 cleanup_event.set_safepointId(safepoint_counter());
413 cleanup_event.commit();
414 }
415 }
416
417 if (PrintSafepointStatistics) {
418 // Record how much time spend on the above cleanup tasks
419 update_statistics_on_cleanup_end(os::javaTimeNanos());
420 }
421 if (begin_event.should_commit()) {
422 begin_event.set_safepointId(safepoint_counter());
423 begin_event.set_totalThreadCount(nof_threads);
424 begin_event.set_jniCriticalThreadCount(_current_jni_active_count);
425 begin_event.commit();
426 }
427 }
428
429 // Wake up all threads, so they are ready to resume execution after the safepoint
430 // operation has been carried out
431 void SafepointSynchronize::end() {
432 EventSafepointEnd event;
433 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id"
434
435 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
436 assert((_safepoint_counter & 0x1) == 1, "must be odd");
437 _safepoint_counter ++;
438 // memory fence isn't required here since an odd _safepoint_counter
439 // value can do no harm and a fence is issued below anyway.
440
441 DEBUG_ONLY(Thread* myThread = Thread::current();)
442 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
443
444 if (PrintSafepointStatistics) {
445 end_statistics(os::javaTimeNanos());
446 }
447
448 #ifdef ASSERT
449 // A pending_exception cannot be installed during a safepoint. The threads
450 // may install an async exception after they come back from a safepoint into
451 // pending_exception after they unblock. But that should happen later.
452 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
453 assert (!(cur->has_pending_exception() &&
454 cur->safepoint_state()->is_at_poll_safepoint()),
455 "safepoint installed a pending exception");
456 }
457 #endif // ASSERT
458
459 if (PageArmed) {
460 // Make polling safepoint aware
461 os::make_polling_page_readable();
462 PageArmed = 0 ;
463 }
464
465 // Remove safepoint check from interpreter
466 Interpreter::ignore_safepoints();
467
468 {
469 MutexLocker mu(Safepoint_lock);
470
471 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
472
473 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
474 // when they get restarted.
475 _state = _not_synchronized;
476 OrderAccess::fence();
477
478 log_debug(safepoint)("Leaving safepoint region");
479
480 // Start suspended threads
481 for(JavaThread *current = Threads::first(); current; current = current->next()) {
482 // A problem occurring on Solaris is when attempting to restart threads
483 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
484 // to the next one (since it has been running the longest). We then have
485 // to wait for a cpu to become available before we can continue restarting
486 // threads.
487 // FIXME: This causes the performance of the VM to degrade when active and with
488 // large numbers of threads. Apparently this is due to the synchronous nature
489 // of suspending threads.
490 //
491 // TODO-FIXME: the comments above are vestigial and no longer apply.
492 // Furthermore, using solaris' schedctl in this particular context confers no benefit
493 if (VMThreadHintNoPreempt) {
494 os::hint_no_preempt();
495 }
496 ThreadSafepointState* cur_state = current->safepoint_state();
497 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
498 cur_state->restart();
499 assert(cur_state->is_running(), "safepoint state has not been reset");
500 }
501
502 RuntimeService::record_safepoint_end();
503
504 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
505 // blocked in signal_thread_blocked
506 Threads_lock->unlock();
507
508 }
509 #if INCLUDE_ALL_GCS
510 // If there are any concurrent GC threads resume them.
511 if (UseConcMarkSweepGC) {
512 ConcurrentMarkSweepThread::desynchronize(false);
513 } else if (UseG1GC) {
514 SuspendibleThreadSet::desynchronize();
515 }
516 #endif // INCLUDE_ALL_GCS
517 // record this time so VMThread can keep track how much time has elapsed
518 // since last safepoint.
519 _end_of_last_safepoint = os::javaTimeMillis();
520
521 if (event.should_commit()) {
522 event.set_safepointId(safepoint_id);
523 event.commit();
524 }
525 }
526
527 bool SafepointSynchronize::is_cleanup_needed() {
528 // Need a safepoint if some inline cache buffers is non-empty
529 if (!InlineCacheBuffer::is_empty()) return true;
530 return false;
531 }
532
533 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) {
534 if (event.should_commit()) {
535 event.set_safepointId(SafepointSynchronize::safepoint_counter());
536 event.set_name(name);
537 event.commit();
538 }
539 }
540
541 // Various cleaning tasks that should be done periodically at safepoints
542 void SafepointSynchronize::do_cleanup_tasks() {
543 {
544 const char* name = "deflating idle monitors";
545 EventSafepointCleanupTask event;
546 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
547 ObjectSynchronizer::deflate_idle_monitors();
548 event_safepoint_cleanup_task_commit(event, name);
549 }
550
551 {
552 const char* name = "updating inline caches";
553 EventSafepointCleanupTask event;
554 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
555 InlineCacheBuffer::update_inline_caches();
556 event_safepoint_cleanup_task_commit(event, name);
557 }
558 {
559 const char* name = "compilation policy safepoint handler";
560 EventSafepointCleanupTask event;
561 TraceTime timer("compilation policy safepoint handler", TRACETIME_LOG(Info, safepoint, cleanup));
562 CompilationPolicy::policy()->do_safepoint_work();
563 event_safepoint_cleanup_task_commit(event, name);
564 }
565
566 {
567 const char* name = "mark nmethods";
568 EventSafepointCleanupTask event;
569 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
570 NMethodSweeper::mark_active_nmethods();
571 event_safepoint_cleanup_task_commit(event, name);
572 }
573
574 if (SymbolTable::needs_rehashing()) {
575 const char* name = "rehashing symbol table";
576 EventSafepointCleanupTask event;
577 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
578 SymbolTable::rehash_table();
579 event_safepoint_cleanup_task_commit(event, name);
580 }
581
582 if (StringTable::needs_rehashing()) {
583 const char* name = "rehashing string table";
584 EventSafepointCleanupTask event;
585 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
586 StringTable::rehash_table();
587 event_safepoint_cleanup_task_commit(event, name);
588 }
589
590 {
591 // CMS delays purging the CLDG until the beginning of the next safepoint and to
592 // make sure concurrent sweep is done
593 const char* name = "purging class loader data graph";
594 EventSafepointCleanupTask event;
595 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
596 ClassLoaderDataGraph::purge_if_needed();
597 event_safepoint_cleanup_task_commit(event, name);
598 }
599 }
600
601
602 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
603 switch(state) {
604 case _thread_in_native:
605 // native threads are safe if they have no java stack or have walkable stack
606 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
607
608 // blocked threads should have already have walkable stack
609 case _thread_blocked:
610 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
611 return true;
612
613 default:
614 return false;
615 }
616 }
617
618
619 // See if the thread is running inside a lazy critical native and
620 // update the thread critical count if so. Also set a suspend flag to
621 // cause the native wrapper to return into the JVM to do the unlock
622 // once the native finishes.
623 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
624 if (state == _thread_in_native &&
625 thread->has_last_Java_frame() &&
626 thread->frame_anchor()->walkable()) {
627 // This thread might be in a critical native nmethod so look at
628 // the top of the stack and increment the critical count if it
629 // is.
630 frame wrapper_frame = thread->last_frame();
631 CodeBlob* stub_cb = wrapper_frame.cb();
632 if (stub_cb != NULL &&
633 stub_cb->is_nmethod() &&
634 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
635 // A thread could potentially be in a critical native across
636 // more than one safepoint, so only update the critical state on
637 // the first one. When it returns it will perform the unlock.
638 if (!thread->do_critical_native_unlock()) {
639 #ifdef ASSERT
640 if (!thread->in_critical()) {
641 GCLocker::increment_debug_jni_lock_count();
642 }
643 #endif
644 thread->enter_critical();
645 // Make sure the native wrapper calls back on return to
646 // perform the needed critical unlock.
647 thread->set_critical_native_unlock();
648 }
649 }
650 }
651 }
652
653
654
655 // -------------------------------------------------------------------------------------------------------
656 // Implementation of Safepoint callback point
657
658 void SafepointSynchronize::block(JavaThread *thread) {
659 assert(thread != NULL, "thread must be set");
660 assert(thread->is_Java_thread(), "not a Java thread");
661
662 // Threads shouldn't block if they are in the middle of printing, but...
663 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
664
665 // Only bail from the block() call if the thread is gone from the
666 // thread list; starting to exit should still block.
667 if (thread->is_terminated()) {
668 // block current thread if we come here from native code when VM is gone
669 thread->block_if_vm_exited();
670
671 // otherwise do nothing
672 return;
673 }
674
675 JavaThreadState state = thread->thread_state();
676 thread->frame_anchor()->make_walkable(thread);
677
678 // Check that we have a valid thread_state at this point
679 switch(state) {
680 case _thread_in_vm_trans:
681 case _thread_in_Java: // From compiled code
682
683 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
684 // we pretend we are still in the VM.
685 thread->set_thread_state(_thread_in_vm);
686
687 if (is_synchronizing()) {
688 Atomic::inc (&TryingToBlock) ;
689 }
690
691 // We will always be holding the Safepoint_lock when we are examine the state
692 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
693 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
694 Safepoint_lock->lock_without_safepoint_check();
695 if (is_synchronizing()) {
696 // Decrement the number of threads to wait for and signal vm thread
697 assert(_waiting_to_block > 0, "sanity check");
698 _waiting_to_block--;
699 thread->safepoint_state()->set_has_called_back(true);
700
701 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
702 if (thread->in_critical()) {
703 // Notice that this thread is in a critical section
704 increment_jni_active_count();
705 }
706
707 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
708 if (_waiting_to_block == 0) {
709 Safepoint_lock->notify_all();
710 }
711 }
712
713 // We transition the thread to state _thread_blocked here, but
714 // we can't do our usual check for external suspension and then
715 // self-suspend after the lock_without_safepoint_check() call
716 // below because we are often called during transitions while
717 // we hold different locks. That would leave us suspended while
718 // holding a resource which results in deadlocks.
719 thread->set_thread_state(_thread_blocked);
720 Safepoint_lock->unlock();
721
722 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
723 // the entire safepoint, the threads will all line up here during the safepoint.
724 Threads_lock->lock_without_safepoint_check();
725 // restore original state. This is important if the thread comes from compiled code, so it
726 // will continue to execute with the _thread_in_Java state.
727 thread->set_thread_state(state);
728 Threads_lock->unlock();
729 break;
730
731 case _thread_in_native_trans:
732 case _thread_blocked_trans:
733 case _thread_new_trans:
734 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
735 thread->print_thread_state();
736 fatal("Deadlock in safepoint code. "
737 "Should have called back to the VM before blocking.");
738 }
739
740 // We transition the thread to state _thread_blocked here, but
741 // we can't do our usual check for external suspension and then
742 // self-suspend after the lock_without_safepoint_check() call
743 // below because we are often called during transitions while
744 // we hold different locks. That would leave us suspended while
745 // holding a resource which results in deadlocks.
746 thread->set_thread_state(_thread_blocked);
747
748 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
749 // the safepoint code might still be waiting for it to block. We need to change the state here,
750 // so it can see that it is at a safepoint.
751
752 // Block until the safepoint operation is completed.
753 Threads_lock->lock_without_safepoint_check();
754
755 // Restore state
756 thread->set_thread_state(state);
757
758 Threads_lock->unlock();
759 break;
760
761 default:
762 fatal("Illegal threadstate encountered: %d", state);
763 }
764
765 // Check for pending. async. exceptions or suspends - except if the
766 // thread was blocked inside the VM. has_special_runtime_exit_condition()
767 // is called last since it grabs a lock and we only want to do that when
768 // we must.
769 //
770 // Note: we never deliver an async exception at a polling point as the
771 // compiler may not have an exception handler for it. The polling
772 // code will notice the async and deoptimize and the exception will
773 // be delivered. (Polling at a return point is ok though). Sure is
774 // a lot of bother for a deprecated feature...
775 //
776 // We don't deliver an async exception if the thread state is
777 // _thread_in_native_trans so JNI functions won't be called with
778 // a surprising pending exception. If the thread state is going back to java,
779 // async exception is checked in check_special_condition_for_native_trans().
780
781 if (state != _thread_blocked_trans &&
782 state != _thread_in_vm_trans &&
783 thread->has_special_runtime_exit_condition()) {
784 thread->handle_special_runtime_exit_condition(
785 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
786 }
787 }
788
789 // ------------------------------------------------------------------------------------------------------
790 // Exception handlers
791
792
793 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
794 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
795 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
796 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
797
798 if (ShowSafepointMsgs) {
799 tty->print("handle_polling_page_exception: ");
800 }
801
802 if (PrintSafepointStatistics) {
803 inc_page_trap_count();
804 }
805
806 ThreadSafepointState* state = thread->safepoint_state();
807
808 state->handle_polling_page_exception();
809 }
810
811
812 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
813 if (!timeout_error_printed) {
814 timeout_error_printed = true;
815 // Print out the thread info which didn't reach the safepoint for debugging
816 // purposes (useful when there are lots of threads in the debugger).
817 tty->cr();
818 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
819 if (reason == _spinning_timeout) {
820 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
821 } else if (reason == _blocking_timeout) {
822 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
823 }
824
825 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
826 ThreadSafepointState *cur_state;
827 ResourceMark rm;
828 for(JavaThread *cur_thread = Threads::first(); cur_thread;
829 cur_thread = cur_thread->next()) {
830 cur_state = cur_thread->safepoint_state();
831
832 if (cur_thread->thread_state() != _thread_blocked &&
833 ((reason == _spinning_timeout && cur_state->is_running()) ||
834 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
835 tty->print("# ");
836 cur_thread->print();
837 tty->cr();
838 }
839 }
840 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
841 }
842
843 // To debug the long safepoint, specify both DieOnSafepointTimeout &
844 // ShowMessageBoxOnError.
845 if (DieOnSafepointTimeout) {
846 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
847 SafepointTimeoutDelay, VMThread::vm_safepoint_description());
848 }
849 }
850
851
852 // -------------------------------------------------------------------------------------------------------
853 // Implementation of ThreadSafepointState
854
855 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
856 _thread = thread;
857 _type = _running;
858 _has_called_back = false;
859 _at_poll_safepoint = false;
860 }
861
862 void ThreadSafepointState::create(JavaThread *thread) {
863 ThreadSafepointState *state = new ThreadSafepointState(thread);
864 thread->set_safepoint_state(state);
865 }
866
867 void ThreadSafepointState::destroy(JavaThread *thread) {
868 if (thread->safepoint_state()) {
869 delete(thread->safepoint_state());
870 thread->set_safepoint_state(NULL);
871 }
872 }
873
874 void ThreadSafepointState::examine_state_of_thread() {
875 assert(is_running(), "better be running or just have hit safepoint poll");
876
877 JavaThreadState state = _thread->thread_state();
878
879 // Save the state at the start of safepoint processing.
880 _orig_thread_state = state;
881
882 // Check for a thread that is suspended. Note that thread resume tries
883 // to grab the Threads_lock which we own here, so a thread cannot be
884 // resumed during safepoint synchronization.
885
886 // We check to see if this thread is suspended without locking to
887 // avoid deadlocking with a third thread that is waiting for this
888 // thread to be suspended. The third thread can notice the safepoint
889 // that we're trying to start at the beginning of its SR_lock->wait()
890 // call. If that happens, then the third thread will block on the
891 // safepoint while still holding the underlying SR_lock. We won't be
892 // able to get the SR_lock and we'll deadlock.
893 //
894 // We don't need to grab the SR_lock here for two reasons:
895 // 1) The suspend flags are both volatile and are set with an
896 // Atomic::cmpxchg() call so we should see the suspended
897 // state right away.
898 // 2) We're being called from the safepoint polling loop; if
899 // we don't see the suspended state on this iteration, then
900 // we'll come around again.
901 //
902 bool is_suspended = _thread->is_ext_suspended();
903 if (is_suspended) {
904 roll_forward(_at_safepoint);
905 return;
906 }
907
908 // Some JavaThread states have an initial safepoint state of
909 // running, but are actually at a safepoint. We will happily
910 // agree and update the safepoint state here.
911 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
912 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
913 roll_forward(_at_safepoint);
914 return;
915 }
916
917 if (state == _thread_in_vm) {
918 roll_forward(_call_back);
919 return;
920 }
921
922 // All other thread states will continue to run until they
923 // transition and self-block in state _blocked
924 // Safepoint polling in compiled code causes the Java threads to do the same.
925 // Note: new threads may require a malloc so they must be allowed to finish
926
927 assert(is_running(), "examine_state_of_thread on non-running thread");
928 return;
929 }
930
931 // Returns true is thread could not be rolled forward at present position.
932 void ThreadSafepointState::roll_forward(suspend_type type) {
933 _type = type;
934
935 switch(_type) {
936 case _at_safepoint:
937 SafepointSynchronize::signal_thread_at_safepoint();
938 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
939 if (_thread->in_critical()) {
940 // Notice that this thread is in a critical section
941 SafepointSynchronize::increment_jni_active_count();
942 }
943 break;
944
945 case _call_back:
946 set_has_called_back(false);
947 break;
948
949 case _running:
950 default:
951 ShouldNotReachHere();
952 }
953 }
954
955 void ThreadSafepointState::restart() {
956 switch(type()) {
957 case _at_safepoint:
958 case _call_back:
959 break;
960
961 case _running:
962 default:
963 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
964 p2i(_thread), _type);
965 _thread->print();
966 ShouldNotReachHere();
967 }
968 _type = _running;
969 set_has_called_back(false);
970 }
971
972
973 void ThreadSafepointState::print_on(outputStream *st) const {
974 const char *s = NULL;
975
976 switch(_type) {
977 case _running : s = "_running"; break;
978 case _at_safepoint : s = "_at_safepoint"; break;
979 case _call_back : s = "_call_back"; break;
980 default:
981 ShouldNotReachHere();
982 }
983
984 st->print_cr("Thread: " INTPTR_FORMAT
985 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
986 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
987 _at_poll_safepoint);
988
989 _thread->print_thread_state_on(st);
990 }
991
992 // ---------------------------------------------------------------------------------------------------------------------
993
994 // Block the thread at the safepoint poll or poll return.
995 void ThreadSafepointState::handle_polling_page_exception() {
996
997 // Check state. block() will set thread state to thread_in_vm which will
998 // cause the safepoint state _type to become _call_back.
999 assert(type() == ThreadSafepointState::_running,
1000 "polling page exception on thread not running state");
1001
1002 // Step 1: Find the nmethod from the return address
1003 if (ShowSafepointMsgs && Verbose) {
1004 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
1005 }
1006 address real_return_addr = thread()->saved_exception_pc();
1007
1008 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1009 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1010 CompiledMethod* nm = (CompiledMethod*)cb;
1011
1012 // Find frame of caller
1013 frame stub_fr = thread()->last_frame();
1014 CodeBlob* stub_cb = stub_fr.cb();
1015 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1016 RegisterMap map(thread(), true);
1017 frame caller_fr = stub_fr.sender(&map);
1018
1019 // Should only be poll_return or poll
1020 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1021
1022 // This is a poll immediately before a return. The exception handling code
1023 // has already had the effect of causing the return to occur, so the execution
1024 // will continue immediately after the call. In addition, the oopmap at the
1025 // return point does not mark the return value as an oop (if it is), so
1026 // it needs a handle here to be updated.
1027 if( nm->is_at_poll_return(real_return_addr) ) {
1028 // See if return type is an oop.
1029 bool return_oop = nm->method()->is_returning_oop();
1030 Handle return_value;
1031 if (return_oop) {
1032 // The oop result has been saved on the stack together with all
1033 // the other registers. In order to preserve it over GCs we need
1034 // to keep it in a handle.
1035 oop result = caller_fr.saved_oop_result(&map);
1036 assert(result == NULL || result->is_oop(), "must be oop");
1037 return_value = Handle(thread(), result);
1038 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1039 }
1040
1041 // Block the thread
1042 SafepointSynchronize::block(thread());
1043
1044 // restore oop result, if any
1045 if (return_oop) {
1046 caller_fr.set_saved_oop_result(&map, return_value());
1047 }
1048 }
1049
1050 // This is a safepoint poll. Verify the return address and block.
1051 else {
1052 set_at_poll_safepoint(true);
1053
1054 // verify the blob built the "return address" correctly
1055 assert(real_return_addr == caller_fr.pc(), "must match");
1056
1057 // Block the thread
1058 SafepointSynchronize::block(thread());
1059 set_at_poll_safepoint(false);
1060
1061 // If we have a pending async exception deoptimize the frame
1062 // as otherwise we may never deliver it.
1063 if (thread()->has_async_condition()) {
1064 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1065 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1066 }
1067
1068 // If an exception has been installed we must check for a pending deoptimization
1069 // Deoptimize frame if exception has been thrown.
1070
1071 if (thread()->has_pending_exception() ) {
1072 RegisterMap map(thread(), true);
1073 frame caller_fr = stub_fr.sender(&map);
1074 if (caller_fr.is_deoptimized_frame()) {
1075 // The exception patch will destroy registers that are still
1076 // live and will be needed during deoptimization. Defer the
1077 // Async exception should have deferred the exception until the
1078 // next safepoint which will be detected when we get into
1079 // the interpreter so if we have an exception now things
1080 // are messed up.
1081
1082 fatal("Exception installed and deoptimization is pending");
1083 }
1084 }
1085 }
1086 }
1087
1088
1089 //
1090 // Statistics & Instrumentations
1091 //
1092 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1093 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1094 int SafepointSynchronize::_cur_stat_index = 0;
1095 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1096 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1097 jlong SafepointSynchronize::_max_sync_time = 0;
1098 jlong SafepointSynchronize::_max_vmop_time = 0;
1099 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1100
1101 static jlong cleanup_end_time = 0;
1102 static bool need_to_track_page_armed_status = false;
1103 static bool init_done = false;
1104
1105 // Helper method to print the header.
1106 static void print_header() {
1107 // The number of spaces is significant here, and should match the format
1108 // specifiers in print_statistics().
1109
1110 tty->print(" vmop "
1111 "[ threads: total initially_running wait_to_block ]"
1112 "[ time: spin block sync cleanup vmop ] ");
1113
1114 // no page armed status printed out if it is always armed.
1115 if (need_to_track_page_armed_status) {
1116 tty->print("page_armed ");
1117 }
1118
1119 tty->print_cr("page_trap_count");
1120 }
1121
1122 void SafepointSynchronize::deferred_initialize_stat() {
1123 if (init_done) return;
1124
1125 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1126 // be printed right away, in which case, _safepoint_stats will regress to
1127 // a single element array. Otherwise, it is a circular ring buffer with default
1128 // size of PrintSafepointStatisticsCount.
1129 int stats_array_size;
1130 if (PrintSafepointStatisticsTimeout > 0) {
1131 stats_array_size = 1;
1132 PrintSafepointStatistics = true;
1133 } else {
1134 stats_array_size = PrintSafepointStatisticsCount;
1135 }
1136 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1137 * sizeof(SafepointStats), mtInternal);
1138 guarantee(_safepoint_stats != NULL,
1139 "not enough memory for safepoint instrumentation data");
1140
1141 if (DeferPollingPageLoopCount >= 0) {
1142 need_to_track_page_armed_status = true;
1143 }
1144 init_done = true;
1145 }
1146
1147 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1148 assert(init_done, "safepoint statistics array hasn't been initialized");
1149 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1150
1151 spstat->_time_stamp = _ts_of_current_safepoint;
1152
1153 VM_Operation *op = VMThread::vm_operation();
1154 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1155 if (op != NULL) {
1156 _safepoint_reasons[spstat->_vmop_type]++;
1157 }
1158
1159 spstat->_nof_total_threads = nof_threads;
1160 spstat->_nof_initial_running_threads = nof_running;
1161 spstat->_nof_threads_hit_page_trap = 0;
1162
1163 // Records the start time of spinning. The real time spent on spinning
1164 // will be adjusted when spin is done. Same trick is applied for time
1165 // spent on waiting for threads to block.
1166 if (nof_running != 0) {
1167 spstat->_time_to_spin = os::javaTimeNanos();
1168 } else {
1169 spstat->_time_to_spin = 0;
1170 }
1171 }
1172
1173 void SafepointSynchronize::update_statistics_on_spin_end() {
1174 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1175
1176 jlong cur_time = os::javaTimeNanos();
1177
1178 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1179 if (spstat->_nof_initial_running_threads != 0) {
1180 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1181 }
1182
1183 if (need_to_track_page_armed_status) {
1184 spstat->_page_armed = (PageArmed == 1);
1185 }
1186
1187 // Records the start time of waiting for to block. Updated when block is done.
1188 if (_waiting_to_block != 0) {
1189 spstat->_time_to_wait_to_block = cur_time;
1190 } else {
1191 spstat->_time_to_wait_to_block = 0;
1192 }
1193 }
1194
1195 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1196 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1197
1198 if (spstat->_nof_threads_wait_to_block != 0) {
1199 spstat->_time_to_wait_to_block = end_time -
1200 spstat->_time_to_wait_to_block;
1201 }
1202
1203 // Records the end time of sync which will be used to calculate the total
1204 // vm operation time. Again, the real time spending in syncing will be deducted
1205 // from the start of the sync time later when end_statistics is called.
1206 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1207 if (spstat->_time_to_sync > _max_sync_time) {
1208 _max_sync_time = spstat->_time_to_sync;
1209 }
1210
1211 spstat->_time_to_do_cleanups = end_time;
1212 }
1213
1214 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1215 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1216
1217 // Record how long spent in cleanup tasks.
1218 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1219
1220 cleanup_end_time = end_time;
1221 }
1222
1223 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1224 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1225
1226 // Update the vm operation time.
1227 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1228 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1229 _max_vmop_time = spstat->_time_to_exec_vmop;
1230 }
1231 // Only the sync time longer than the specified
1232 // PrintSafepointStatisticsTimeout will be printed out right away.
1233 // By default, it is -1 meaning all samples will be put into the list.
1234 if ( PrintSafepointStatisticsTimeout > 0) {
1235 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1236 print_statistics();
1237 }
1238 } else {
1239 // The safepoint statistics will be printed out when the _safepoin_stats
1240 // array fills up.
1241 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1242 print_statistics();
1243 _cur_stat_index = 0;
1244 } else {
1245 _cur_stat_index++;
1246 }
1247 }
1248 }
1249
1250 void SafepointSynchronize::print_statistics() {
1251 for (int index = 0; index <= _cur_stat_index; index++) {
1252 if (index % 30 == 0) {
1253 print_header();
1254 }
1255 SafepointStats* sstats = &_safepoint_stats[index];
1256 tty->print("%8.3f: ", sstats->_time_stamp);
1257 tty->print("%-30s [ "
1258 INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " "
1259 "]",
1260 (sstats->_vmop_type == -1 ? "no vm operation" : VM_Operation::name(sstats->_vmop_type)),
1261 sstats->_nof_total_threads,
1262 sstats->_nof_initial_running_threads,
1263 sstats->_nof_threads_wait_to_block);
1264 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1265 tty->print("[ "
1266 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1267 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1268 INT64_FORMAT_W(7) " ] ",
1269 sstats->_time_to_spin / MICROUNITS,
1270 sstats->_time_to_wait_to_block / MICROUNITS,
1271 sstats->_time_to_sync / MICROUNITS,
1272 sstats->_time_to_do_cleanups / MICROUNITS,
1273 sstats->_time_to_exec_vmop / MICROUNITS);
1274
1275 if (need_to_track_page_armed_status) {
1276 tty->print(INT32_FORMAT_W(10) " ", sstats->_page_armed);
1277 }
1278 tty->print_cr(INT32_FORMAT_W(15) " ", sstats->_nof_threads_hit_page_trap);
1279 }
1280 }
1281
1282 // This method will be called when VM exits. It will first call
1283 // print_statistics to print out the rest of the sampling. Then
1284 // it tries to summarize the sampling.
1285 void SafepointSynchronize::print_stat_on_exit() {
1286 if (_safepoint_stats == NULL) return;
1287
1288 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1289
1290 // During VM exit, end_statistics may not get called and in that
1291 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1292 // don't print it out.
1293 // Approximate the vm op time.
1294 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1295 os::javaTimeNanos() - cleanup_end_time;
1296
1297 if ( PrintSafepointStatisticsTimeout < 0 ||
1298 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1299 print_statistics();
1300 }
1301 tty->cr();
1302
1303 // Print out polling page sampling status.
1304 if (!need_to_track_page_armed_status) {
1305 tty->print_cr("Polling page always armed");
1306 } else {
1307 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
1308 DeferPollingPageLoopCount);
1309 }
1310
1311 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1312 if (_safepoint_reasons[index] != 0) {
1313 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1314 _safepoint_reasons[index]);
1315 }
1316 }
1317
1318 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1319 _coalesced_vmop_count);
1320 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1321 _max_sync_time / MICROUNITS);
1322 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1323 INT64_FORMAT_W(5) " ms",
1324 _max_vmop_time / MICROUNITS);
1325 }
1326
1327 // ------------------------------------------------------------------------------------------------
1328 // Non-product code
1329
1330 #ifndef PRODUCT
1331
1332 void SafepointSynchronize::print_state() {
1333 if (_state == _not_synchronized) {
1334 tty->print_cr("not synchronized");
1335 } else if (_state == _synchronizing || _state == _synchronized) {
1336 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1337 "synchronized");
1338
1339 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1340 cur->safepoint_state()->print();
1341 }
1342 }
1343 }
1344
1345 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1346 if (ShowSafepointMsgs) {
1347 va_list ap;
1348 va_start(ap, format);
1349 tty->vprint_cr(format, ap);
1350 va_end(ap);
1351 }
1352 }
1353
1354 #endif // !PRODUCT