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 "gc/shared/strongRootsScope.hpp"
37 #include "gc/shared/workgroup.hpp"
38 #include "interpreter/interpreter.hpp"
39 #include "logging/log.hpp"
40 #include "logging/logStream.hpp"
41 #include "memory/resourceArea.hpp"
42 #include "memory/universe.inline.hpp"
43 #include "oops/oop.inline.hpp"
44 #include "oops/symbol.hpp"
45 #include "runtime/atomic.hpp"
46 #include "runtime/compilationPolicy.hpp"
47 #include "runtime/deoptimization.hpp"
48 #include "runtime/frame.inline.hpp"
49 #include "runtime/interfaceSupport.hpp"
50 #include "runtime/mutexLocker.hpp"
51 #include "runtime/orderAccess.inline.hpp"
52 #include "runtime/osThread.hpp"
53 #include "runtime/safepoint.hpp"
54 #include "runtime/signature.hpp"
55 #include "runtime/stubCodeGenerator.hpp"
56 #include "runtime/stubRoutines.hpp"
57 #include "runtime/sweeper.hpp"
58 #include "runtime/synchronizer.hpp"
59 #include "runtime/thread.inline.hpp"
60 #include "runtime/timerTrace.hpp"
61 #include "services/runtimeService.hpp"
62 #include "trace/tracing.hpp"
63 #include "trace/traceMacros.hpp"
64 #include "utilities/events.hpp"
65 #include "utilities/macros.hpp"
66 #if INCLUDE_ALL_GCS
67 #include "gc/cms/concurrentMarkSweepThread.hpp"
68 #include "gc/g1/suspendibleThreadSet.hpp"
69 #endif // INCLUDE_ALL_GCS
70 #ifdef COMPILER1
71 #include "c1/c1_globals.hpp"
72 #endif
73
74 // --------------------------------------------------------------------------------------------------
75 // Implementation of Safepoint begin/end
76
77 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
78 volatile int SafepointSynchronize::_waiting_to_block = 0;
79 volatile int SafepointSynchronize::_safepoint_counter = 0;
80 int SafepointSynchronize::_current_jni_active_count = 0;
81 long SafepointSynchronize::_end_of_last_safepoint = 0;
82 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
83 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
84 static bool timeout_error_printed = false;
85
86 // Roll all threads forward to a safepoint and suspend them all
87 void SafepointSynchronize::begin() {
88 EventSafepointBegin begin_event;
89 Thread* myThread = Thread::current();
90 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
91
92 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
93 _safepoint_begin_time = os::javaTimeNanos();
94 _ts_of_current_safepoint = tty->time_stamp().seconds();
95 }
96
97 #if INCLUDE_ALL_GCS
98 if (UseConcMarkSweepGC) {
99 // In the future we should investigate whether CMS can use the
100 // more-general mechanism below. DLD (01/05).
101 ConcurrentMarkSweepThread::synchronize(false);
102 } else if (UseG1GC) {
103 SuspendibleThreadSet::synchronize();
104 }
105 #endif // INCLUDE_ALL_GCS
106
107 // By getting the Threads_lock, we assure that no threads are about to start or
108 // exit. It is released again in SafepointSynchronize::end().
109 Threads_lock->lock();
110
111 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
112
113 int nof_threads = Threads::number_of_threads();
114
115 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads);
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 = 0;
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 {
179 EventSafepointStateSynchronization sync_event;
180 int initial_running = 0;
181
182 _state = _synchronizing;
183 OrderAccess::fence();
184
185 // Flush all thread states to memory
186 if (!UseMembar) {
187 os::serialize_thread_states();
188 }
189
190 // Make interpreter safepoint aware
191 Interpreter::notice_safepoints();
192
193 if (DeferPollingPageLoopCount < 0) {
194 // Make polling safepoint aware
195 guarantee (PageArmed == 0, "invariant") ;
196 PageArmed = 1 ;
197 os::make_polling_page_unreadable();
198 }
199
200 // Consider using active_processor_count() ... but that call is expensive.
201 int ncpus = os::processor_count() ;
202
203 #ifdef ASSERT
204 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
205 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
206 // Clear the visited flag to ensure that the critical counts are collected properly.
207 cur->set_visited_for_critical_count(false);
208 }
209 #endif // ASSERT
210
211 if (SafepointTimeout)
212 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
213
214 // Iterate through all threads until it have been determined how to stop them all at a safepoint
215 unsigned int iterations = 0;
216 int steps = 0 ;
217 while(still_running > 0) {
218 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
219 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
220 ThreadSafepointState *cur_state = cur->safepoint_state();
221 if (cur_state->is_running()) {
222 cur_state->examine_state_of_thread();
223 if (!cur_state->is_running()) {
224 still_running--;
225 // consider adjusting steps downward:
226 // steps = 0
227 // steps -= NNN
228 // steps >>= 1
229 // steps = MIN(steps, 2000-100)
230 // if (iterations != 0) steps -= NNN
231 }
232 LogTarget(Trace, safepoint) lt;
233 if (lt.is_enabled()) {
234 ResourceMark rm;
235 LogStream ls(lt);
236 cur_state->print_on(&ls);
237 }
238 }
239 }
240
241 if (iterations == 0) {
242 initial_running = still_running;
243 if (PrintSafepointStatistics) {
244 begin_statistics(nof_threads, still_running);
245 }
246 }
247
248 if (still_running > 0) {
249 // Check for if it takes to long
250 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
251 print_safepoint_timeout(_spinning_timeout);
252 }
253
254 // Spin to avoid context switching.
255 // There's a tension between allowing the mutators to run (and rendezvous)
256 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
257 // a mutator might otherwise use profitably to reach a safepoint. Excessive
258 // spinning by the VM thread on a saturated system can increase rendezvous latency.
259 // Blocking or yielding incur their own penalties in the form of context switching
260 // and the resultant loss of $ residency.
261 //
262 // Further complicating matters is that yield() does not work as naively expected
263 // on many platforms -- yield() does not guarantee that any other ready threads
264 // will run. As such we revert to naked_short_sleep() after some number of iterations.
265 // nakes_short_sleep() is implemented as a short unconditional sleep.
266 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
267 // can actually increase the time it takes the VM thread to detect that a system-wide
268 // stop-the-world safepoint has been reached. In a pathological scenario such as that
269 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
270 // In that case the mutators will be stalled waiting for the safepoint to complete and the
271 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
272 // will eventually wake up and detect that all mutators are safe, at which point
273 // we'll again make progress.
274 //
275 // Beware too that that the VMThread typically runs at elevated priority.
276 // Its default priority is higher than the default mutator priority.
277 // Obviously, this complicates spinning.
278 //
279 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
280 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
281 //
282 // See the comments in synchronizer.cpp for additional remarks on spinning.
283 //
284 // In the future we might:
285 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
286 // This is tricky as the path used by a thread exiting the JVM (say on
287 // on JNI call-out) simply stores into its state field. The burden
288 // is placed on the VM thread, which must poll (spin).
289 // 2. Find something useful to do while spinning. If the safepoint is GC-related
290 // we might aggressively scan the stacks of threads that are already safe.
291 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
292 // If all the mutators are ONPROC there's no reason to sleep or yield.
293 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
294 // 5. Check system saturation. If the system is not fully saturated then
295 // simply spin and avoid sleep/yield.
296 // 6. As still-running mutators rendezvous they could unpark the sleeping
297 // VMthread. This works well for still-running mutators that become
298 // safe. The VMthread must still poll for mutators that call-out.
299 // 7. Drive the policy on time-since-begin instead of iterations.
300 // 8. Consider making the spin duration a function of the # of CPUs:
301 // Spin = (((ncpus-1) * M) + K) + F(still_running)
302 // Alternately, instead of counting iterations of the outer loop
303 // we could count the # of threads visited in the inner loop, above.
304 // 9. On windows consider using the return value from SwitchThreadTo()
305 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
306
307 if (int(iterations) == DeferPollingPageLoopCount) {
308 guarantee (PageArmed == 0, "invariant") ;
309 PageArmed = 1 ;
310 os::make_polling_page_unreadable();
311 }
312
313 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
314 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
315 ++steps ;
316 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
317 SpinPause() ; // MP-Polite spin
318 } else
319 if (steps < DeferThrSuspendLoopCount) {
320 os::naked_yield() ;
321 } else {
322 os::naked_short_sleep(1);
323 }
324
325 iterations ++ ;
326 }
327 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
328 }
329 assert(still_running == 0, "sanity check");
330
331 if (PrintSafepointStatistics) {
332 update_statistics_on_spin_end();
333 }
334
335 if (sync_event.should_commit()) {
336 sync_event.set_safepointId(safepoint_counter());
337 sync_event.set_initialThreadCount(initial_running);
338 sync_event.set_runningThreadCount(_waiting_to_block);
339 sync_event.set_iterations(iterations);
340 sync_event.commit();
341 }
342 } //EventSafepointStateSync
343
344 // wait until all threads are stopped
345 {
346 EventSafepointWaitBlocked wait_blocked_event;
347 int initial_waiting_to_block = _waiting_to_block;
348
349 while (_waiting_to_block > 0) {
350 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
351 if (!SafepointTimeout || timeout_error_printed) {
352 Safepoint_lock->wait(true); // true, means with no safepoint checks
353 } else {
354 // Compute remaining time
355 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
356
357 // If there is no remaining time, then there is an error
358 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
359 print_safepoint_timeout(_blocking_timeout);
360 }
361 }
362 }
363 assert(_waiting_to_block == 0, "sanity check");
364
365 #ifndef PRODUCT
366 if (SafepointTimeout) {
367 jlong current_time = os::javaTimeNanos();
368 if (safepoint_limit_time < current_time) {
369 tty->print_cr("# SafepointSynchronize: Finished after "
370 INT64_FORMAT_W(6) " ms",
371 (int64_t)((current_time - safepoint_limit_time) / MICROUNITS +
372 (jlong)SafepointTimeoutDelay));
373 }
374 }
375 #endif
376
377 assert((_safepoint_counter & 0x1) == 0, "must be even");
378 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
379 _safepoint_counter ++;
380
381 // Record state
382 _state = _synchronized;
383
384 OrderAccess::fence();
385
386 if (wait_blocked_event.should_commit()) {
387 wait_blocked_event.set_safepointId(safepoint_counter());
388 wait_blocked_event.set_runningThreadCount(initial_waiting_to_block);
389 wait_blocked_event.commit();
390 }
391 } // EventSafepointWaitBlocked
392
393 #ifdef ASSERT
394 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
395 // make sure all the threads were visited
396 assert(cur->was_visited_for_critical_count(), "missed a thread");
397 }
398 #endif // ASSERT
399
400 // Update the count of active JNI critical regions
401 GCLocker::set_jni_lock_count(_current_jni_active_count);
402
403 if (log_is_enabled(Debug, safepoint)) {
404 log_debug(safepoint)("Entering safepoint region: %s", VMThread::vm_safepoint_description());
405 }
406
407 RuntimeService::record_safepoint_synchronized();
408 if (PrintSafepointStatistics) {
409 update_statistics_on_sync_end(os::javaTimeNanos());
410 }
411
412 // Call stuff that needs to be run when a safepoint is just about to be completed
413 {
414 EventSafepointCleanup cleanup_event;
415 do_cleanup_tasks();
416 if (cleanup_event.should_commit()) {
417 cleanup_event.set_safepointId(safepoint_counter());
418 cleanup_event.commit();
419 }
420 }
421
422 if (PrintSafepointStatistics) {
423 // Record how much time spend on the above cleanup tasks
424 update_statistics_on_cleanup_end(os::javaTimeNanos());
425 }
426 if (begin_event.should_commit()) {
427 begin_event.set_safepointId(safepoint_counter());
428 begin_event.set_totalThreadCount(nof_threads);
429 begin_event.set_jniCriticalThreadCount(_current_jni_active_count);
430 begin_event.commit();
431 }
432 }
433
434 // Wake up all threads, so they are ready to resume execution after the safepoint
435 // operation has been carried out
436 void SafepointSynchronize::end() {
437 EventSafepointEnd event;
438 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id"
439
440 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
441 assert((_safepoint_counter & 0x1) == 1, "must be odd");
442 _safepoint_counter ++;
443 // memory fence isn't required here since an odd _safepoint_counter
444 // value can do no harm and a fence is issued below anyway.
445
446 DEBUG_ONLY(Thread* myThread = Thread::current();)
447 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
448
449 if (PrintSafepointStatistics) {
450 end_statistics(os::javaTimeNanos());
451 }
452
453 #ifdef ASSERT
454 // A pending_exception cannot be installed during a safepoint. The threads
455 // may install an async exception after they come back from a safepoint into
456 // pending_exception after they unblock. But that should happen later.
457 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
458 assert (!(cur->has_pending_exception() &&
459 cur->safepoint_state()->is_at_poll_safepoint()),
460 "safepoint installed a pending exception");
461 }
462 #endif // ASSERT
463
464 if (PageArmed) {
465 // Make polling safepoint aware
466 os::make_polling_page_readable();
467 PageArmed = 0 ;
468 }
469
470 // Remove safepoint check from interpreter
471 Interpreter::ignore_safepoints();
472
473 {
474 MutexLocker mu(Safepoint_lock);
475
476 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
477
478 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
479 // when they get restarted.
480 _state = _not_synchronized;
481 OrderAccess::fence();
482
483 log_debug(safepoint)("Leaving safepoint region");
484
485 // Start suspended threads
486 for(JavaThread *current = Threads::first(); current; current = current->next()) {
487 // A problem occurring on Solaris is when attempting to restart threads
488 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
489 // to the next one (since it has been running the longest). We then have
490 // to wait for a cpu to become available before we can continue restarting
491 // threads.
492 // FIXME: This causes the performance of the VM to degrade when active and with
493 // large numbers of threads. Apparently this is due to the synchronous nature
494 // of suspending threads.
495 //
496 // TODO-FIXME: the comments above are vestigial and no longer apply.
497 // Furthermore, using solaris' schedctl in this particular context confers no benefit
498 if (VMThreadHintNoPreempt) {
499 os::hint_no_preempt();
500 }
501 ThreadSafepointState* cur_state = current->safepoint_state();
502 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
503 cur_state->restart();
504 assert(cur_state->is_running(), "safepoint state has not been reset");
505 }
506
507 RuntimeService::record_safepoint_end();
508
509 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
510 // blocked in signal_thread_blocked
511 Threads_lock->unlock();
512
513 }
514 #if INCLUDE_ALL_GCS
515 // If there are any concurrent GC threads resume them.
516 if (UseConcMarkSweepGC) {
517 ConcurrentMarkSweepThread::desynchronize(false);
518 } else if (UseG1GC) {
519 SuspendibleThreadSet::desynchronize();
520 }
521 #endif // INCLUDE_ALL_GCS
522 // record this time so VMThread can keep track how much time has elapsed
523 // since last safepoint.
524 _end_of_last_safepoint = os::javaTimeMillis();
525
526 if (event.should_commit()) {
527 event.set_safepointId(safepoint_id);
528 event.commit();
529 }
530 }
531
532 bool SafepointSynchronize::is_cleanup_needed() {
533 // Need a safepoint if there are many monitors to deflate.
534 if (ObjectSynchronizer::is_cleanup_needed()) return true;
535 // Need a safepoint if some inline cache buffers is non-empty
536 if (!InlineCacheBuffer::is_empty()) return true;
537 return false;
538 }
539
540 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) {
541 if (event.should_commit()) {
542 event.set_safepointId(SafepointSynchronize::safepoint_counter());
543 event.set_name(name);
544 event.commit();
545 }
546 }
547
548 class ParallelSPCleanupThreadClosure : public ThreadClosure {
549 private:
550 CodeBlobClosure* _nmethod_cl;
551 DeflateMonitorCounters* _counters;
552
553 public:
554 ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) :
555 _counters(counters),
556 _nmethod_cl(NMethodSweeper::prepare_mark_active_nmethods()) {}
557
558 void do_thread(Thread* thread) {
559 ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters);
560 if (_nmethod_cl != NULL && thread->is_Java_thread() &&
561 ! thread->is_Code_cache_sweeper_thread()) {
562 JavaThread* jt = (JavaThread*) thread;
563 jt->nmethods_do(_nmethod_cl);
564 }
565 }
566 };
567
568 class ParallelSPCleanupTask : public AbstractGangTask {
569 private:
570 SubTasksDone _subtasks;
571 ParallelSPCleanupThreadClosure _cleanup_threads_cl;
572 uint _num_workers;
573 DeflateMonitorCounters* _counters;
574 public:
575 ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
576 AbstractGangTask("Parallel Safepoint Cleanup"),
577 _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
578 _num_workers(num_workers),
579 _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)),
580 _counters(counters) {}
581
582 void work(uint worker_id) {
583 // All threads deflate monitors and mark nmethods (if necessary).
584 Threads::parallel_java_threads_do(&_cleanup_threads_cl);
585
586 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
587 const char* name = "deflating idle monitors";
588 EventSafepointCleanupTask event;
589 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
590 ObjectSynchronizer::deflate_idle_monitors(_counters);
591 event_safepoint_cleanup_task_commit(event, name);
592 }
593
594 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
595 const char* name = "updating inline caches";
596 EventSafepointCleanupTask event;
597 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
598 InlineCacheBuffer::update_inline_caches();
599 event_safepoint_cleanup_task_commit(event, name);
600 }
601
602 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
603 const char* name = "compilation policy safepoint handler";
604 EventSafepointCleanupTask event;
605 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
606 CompilationPolicy::policy()->do_safepoint_work();
607 event_safepoint_cleanup_task_commit(event, name);
608 }
609
610 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
611 if (SymbolTable::needs_rehashing()) {
612 const char* name = "rehashing symbol table";
613 EventSafepointCleanupTask event;
614 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
615 SymbolTable::rehash_table();
616 event_safepoint_cleanup_task_commit(event, name);
617 }
618 }
619
620 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
621 if (StringTable::needs_rehashing()) {
622 const char* name = "rehashing string table";
623 EventSafepointCleanupTask event;
624 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
625 StringTable::rehash_table();
626 event_safepoint_cleanup_task_commit(event, name);
627 }
628 }
629
630 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) {
631 // CMS delays purging the CLDG until the beginning of the next safepoint and to
632 // make sure concurrent sweep is done
633 const char* name = "purging class loader data graph";
634 EventSafepointCleanupTask event;
635 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
636 ClassLoaderDataGraph::purge_if_needed();
637 event_safepoint_cleanup_task_commit(event, name);
638 }
639 _subtasks.all_tasks_completed(_num_workers);
640 }
641 };
642
643 // Various cleaning tasks that should be done periodically at safepoints.
644 void SafepointSynchronize::do_cleanup_tasks() {
645
646 TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup));
647
648 // Prepare for monitor deflation.
649 DeflateMonitorCounters deflate_counters;
650 ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
651
652 CollectedHeap* heap = Universe::heap();
653 assert(heap != NULL, "heap not initialized yet?");
654 WorkGang* cleanup_workers = heap->get_safepoint_workers();
655 if (cleanup_workers != NULL) {
656 // Parallel cleanup using GC provided thread pool.
657 uint num_cleanup_workers = cleanup_workers->active_workers();
658 ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
659 StrongRootsScope srs(num_cleanup_workers);
660 cleanup_workers->run_task(&cleanup);
661 } else {
662 // Serial cleanup using VMThread.
663 ParallelSPCleanupTask cleanup(1, &deflate_counters);
664 StrongRootsScope srs(1);
665 cleanup.work(0);
666 }
667
668 // Finish monitor deflation.
669 ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
670 }
671
672
673 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
674 switch(state) {
675 case _thread_in_native:
676 // native threads are safe if they have no java stack or have walkable stack
677 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
678
679 // blocked threads should have already have walkable stack
680 case _thread_blocked:
681 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
682 return true;
683
684 default:
685 return false;
686 }
687 }
688
689
690 // See if the thread is running inside a lazy critical native and
691 // update the thread critical count if so. Also set a suspend flag to
692 // cause the native wrapper to return into the JVM to do the unlock
693 // once the native finishes.
694 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
695 if (state == _thread_in_native &&
696 thread->has_last_Java_frame() &&
697 thread->frame_anchor()->walkable()) {
698 // This thread might be in a critical native nmethod so look at
699 // the top of the stack and increment the critical count if it
700 // is.
701 frame wrapper_frame = thread->last_frame();
702 CodeBlob* stub_cb = wrapper_frame.cb();
703 if (stub_cb != NULL &&
704 stub_cb->is_nmethod() &&
705 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
706 // A thread could potentially be in a critical native across
707 // more than one safepoint, so only update the critical state on
708 // the first one. When it returns it will perform the unlock.
709 if (!thread->do_critical_native_unlock()) {
710 #ifdef ASSERT
711 if (!thread->in_critical()) {
712 GCLocker::increment_debug_jni_lock_count();
713 }
714 #endif
715 thread->enter_critical();
716 // Make sure the native wrapper calls back on return to
717 // perform the needed critical unlock.
718 thread->set_critical_native_unlock();
719 }
720 }
721 }
722 }
723
724
725
726 // -------------------------------------------------------------------------------------------------------
727 // Implementation of Safepoint callback point
728
729 void SafepointSynchronize::block(JavaThread *thread) {
730 assert(thread != NULL, "thread must be set");
731 assert(thread->is_Java_thread(), "not a Java thread");
732
733 // Threads shouldn't block if they are in the middle of printing, but...
734 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
735
736 // Only bail from the block() call if the thread is gone from the
737 // thread list; starting to exit should still block.
738 if (thread->is_terminated()) {
739 // block current thread if we come here from native code when VM is gone
740 thread->block_if_vm_exited();
741
742 // otherwise do nothing
743 return;
744 }
745
746 JavaThreadState state = thread->thread_state();
747 thread->frame_anchor()->make_walkable(thread);
748
749 // Check that we have a valid thread_state at this point
750 switch(state) {
751 case _thread_in_vm_trans:
752 case _thread_in_Java: // From compiled code
753
754 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
755 // we pretend we are still in the VM.
756 thread->set_thread_state(_thread_in_vm);
757
758 if (is_synchronizing()) {
759 Atomic::inc (&TryingToBlock) ;
760 }
761
762 // We will always be holding the Safepoint_lock when we are examine the state
763 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
764 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
765 Safepoint_lock->lock_without_safepoint_check();
766 if (is_synchronizing()) {
767 // Decrement the number of threads to wait for and signal vm thread
768 assert(_waiting_to_block > 0, "sanity check");
769 _waiting_to_block--;
770 thread->safepoint_state()->set_has_called_back(true);
771
772 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
773 if (thread->in_critical()) {
774 // Notice that this thread is in a critical section
775 increment_jni_active_count();
776 }
777
778 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
779 if (_waiting_to_block == 0) {
780 Safepoint_lock->notify_all();
781 }
782 }
783
784 // We transition the thread to state _thread_blocked here, but
785 // we can't do our usual check for external suspension and then
786 // self-suspend after the lock_without_safepoint_check() call
787 // below because we are often called during transitions while
788 // we hold different locks. That would leave us suspended while
789 // holding a resource which results in deadlocks.
790 thread->set_thread_state(_thread_blocked);
791 Safepoint_lock->unlock();
792
793 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
794 // the entire safepoint, the threads will all line up here during the safepoint.
795 Threads_lock->lock_without_safepoint_check();
796 // restore original state. This is important if the thread comes from compiled code, so it
797 // will continue to execute with the _thread_in_Java state.
798 thread->set_thread_state(state);
799 Threads_lock->unlock();
800 break;
801
802 case _thread_in_native_trans:
803 case _thread_blocked_trans:
804 case _thread_new_trans:
805 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
806 thread->print_thread_state();
807 fatal("Deadlock in safepoint code. "
808 "Should have called back to the VM before blocking.");
809 }
810
811 // We transition the thread to state _thread_blocked here, but
812 // we can't do our usual check for external suspension and then
813 // self-suspend after the lock_without_safepoint_check() call
814 // below because we are often called during transitions while
815 // we hold different locks. That would leave us suspended while
816 // holding a resource which results in deadlocks.
817 thread->set_thread_state(_thread_blocked);
818
819 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
820 // the safepoint code might still be waiting for it to block. We need to change the state here,
821 // so it can see that it is at a safepoint.
822
823 // Block until the safepoint operation is completed.
824 Threads_lock->lock_without_safepoint_check();
825
826 // Restore state
827 thread->set_thread_state(state);
828
829 Threads_lock->unlock();
830 break;
831
832 default:
833 fatal("Illegal threadstate encountered: %d", state);
834 }
835
836 // Check for pending. async. exceptions or suspends - except if the
837 // thread was blocked inside the VM. has_special_runtime_exit_condition()
838 // is called last since it grabs a lock and we only want to do that when
839 // we must.
840 //
841 // Note: we never deliver an async exception at a polling point as the
842 // compiler may not have an exception handler for it. The polling
843 // code will notice the async and deoptimize and the exception will
844 // be delivered. (Polling at a return point is ok though). Sure is
845 // a lot of bother for a deprecated feature...
846 //
847 // We don't deliver an async exception if the thread state is
848 // _thread_in_native_trans so JNI functions won't be called with
849 // a surprising pending exception. If the thread state is going back to java,
850 // async exception is checked in check_special_condition_for_native_trans().
851
852 if (state != _thread_blocked_trans &&
853 state != _thread_in_vm_trans &&
854 thread->has_special_runtime_exit_condition()) {
855 thread->handle_special_runtime_exit_condition(
856 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
857 }
858 }
859
860 // ------------------------------------------------------------------------------------------------------
861 // Exception handlers
862
863
864 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
865 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
866 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
867 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
868
869 if (ShowSafepointMsgs) {
870 tty->print("handle_polling_page_exception: ");
871 }
872
873 if (PrintSafepointStatistics) {
874 inc_page_trap_count();
875 }
876
877 ThreadSafepointState* state = thread->safepoint_state();
878
879 state->handle_polling_page_exception();
880 }
881
882
883 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
884 if (!timeout_error_printed) {
885 timeout_error_printed = true;
886 // Print out the thread info which didn't reach the safepoint for debugging
887 // purposes (useful when there are lots of threads in the debugger).
888 tty->cr();
889 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
890 if (reason == _spinning_timeout) {
891 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
892 } else if (reason == _blocking_timeout) {
893 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
894 }
895
896 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
897 ThreadSafepointState *cur_state;
898 ResourceMark rm;
899 for(JavaThread *cur_thread = Threads::first(); cur_thread;
900 cur_thread = cur_thread->next()) {
901 cur_state = cur_thread->safepoint_state();
902
903 if (cur_thread->thread_state() != _thread_blocked &&
904 ((reason == _spinning_timeout && cur_state->is_running()) ||
905 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
906 tty->print("# ");
907 cur_thread->print();
908 tty->cr();
909 }
910 }
911 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
912 }
913
914 // To debug the long safepoint, specify both DieOnSafepointTimeout &
915 // ShowMessageBoxOnError.
916 if (DieOnSafepointTimeout) {
917 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
918 SafepointTimeoutDelay, VMThread::vm_safepoint_description());
919 }
920 }
921
922
923 // -------------------------------------------------------------------------------------------------------
924 // Implementation of ThreadSafepointState
925
926 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
927 _thread = thread;
928 _type = _running;
929 _has_called_back = false;
930 _at_poll_safepoint = false;
931 }
932
933 void ThreadSafepointState::create(JavaThread *thread) {
934 ThreadSafepointState *state = new ThreadSafepointState(thread);
935 thread->set_safepoint_state(state);
936 }
937
938 void ThreadSafepointState::destroy(JavaThread *thread) {
939 if (thread->safepoint_state()) {
940 delete(thread->safepoint_state());
941 thread->set_safepoint_state(NULL);
942 }
943 }
944
945 void ThreadSafepointState::examine_state_of_thread() {
946 assert(is_running(), "better be running or just have hit safepoint poll");
947
948 JavaThreadState state = _thread->thread_state();
949
950 // Save the state at the start of safepoint processing.
951 _orig_thread_state = state;
952
953 // Check for a thread that is suspended. Note that thread resume tries
954 // to grab the Threads_lock which we own here, so a thread cannot be
955 // resumed during safepoint synchronization.
956
957 // We check to see if this thread is suspended without locking to
958 // avoid deadlocking with a third thread that is waiting for this
959 // thread to be suspended. The third thread can notice the safepoint
960 // that we're trying to start at the beginning of its SR_lock->wait()
961 // call. If that happens, then the third thread will block on the
962 // safepoint while still holding the underlying SR_lock. We won't be
963 // able to get the SR_lock and we'll deadlock.
964 //
965 // We don't need to grab the SR_lock here for two reasons:
966 // 1) The suspend flags are both volatile and are set with an
967 // Atomic::cmpxchg() call so we should see the suspended
968 // state right away.
969 // 2) We're being called from the safepoint polling loop; if
970 // we don't see the suspended state on this iteration, then
971 // we'll come around again.
972 //
973 bool is_suspended = _thread->is_ext_suspended();
974 if (is_suspended) {
975 roll_forward(_at_safepoint);
976 return;
977 }
978
979 // Some JavaThread states have an initial safepoint state of
980 // running, but are actually at a safepoint. We will happily
981 // agree and update the safepoint state here.
982 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
983 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
984 roll_forward(_at_safepoint);
985 return;
986 }
987
988 if (state == _thread_in_vm) {
989 roll_forward(_call_back);
990 return;
991 }
992
993 // All other thread states will continue to run until they
994 // transition and self-block in state _blocked
995 // Safepoint polling in compiled code causes the Java threads to do the same.
996 // Note: new threads may require a malloc so they must be allowed to finish
997
998 assert(is_running(), "examine_state_of_thread on non-running thread");
999 return;
1000 }
1001
1002 // Returns true is thread could not be rolled forward at present position.
1003 void ThreadSafepointState::roll_forward(suspend_type type) {
1004 _type = type;
1005
1006 switch(_type) {
1007 case _at_safepoint:
1008 SafepointSynchronize::signal_thread_at_safepoint();
1009 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
1010 if (_thread->in_critical()) {
1011 // Notice that this thread is in a critical section
1012 SafepointSynchronize::increment_jni_active_count();
1013 }
1014 break;
1015
1016 case _call_back:
1017 set_has_called_back(false);
1018 break;
1019
1020 case _running:
1021 default:
1022 ShouldNotReachHere();
1023 }
1024 }
1025
1026 void ThreadSafepointState::restart() {
1027 switch(type()) {
1028 case _at_safepoint:
1029 case _call_back:
1030 break;
1031
1032 case _running:
1033 default:
1034 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
1035 p2i(_thread), _type);
1036 _thread->print();
1037 ShouldNotReachHere();
1038 }
1039 _type = _running;
1040 set_has_called_back(false);
1041 }
1042
1043
1044 void ThreadSafepointState::print_on(outputStream *st) const {
1045 const char *s = NULL;
1046
1047 switch(_type) {
1048 case _running : s = "_running"; break;
1049 case _at_safepoint : s = "_at_safepoint"; break;
1050 case _call_back : s = "_call_back"; break;
1051 default:
1052 ShouldNotReachHere();
1053 }
1054
1055 st->print_cr("Thread: " INTPTR_FORMAT
1056 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1057 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
1058 _at_poll_safepoint);
1059
1060 _thread->print_thread_state_on(st);
1061 }
1062
1063 // ---------------------------------------------------------------------------------------------------------------------
1064
1065 // Block the thread at the safepoint poll or poll return.
1066 void ThreadSafepointState::handle_polling_page_exception() {
1067
1068 // Check state. block() will set thread state to thread_in_vm which will
1069 // cause the safepoint state _type to become _call_back.
1070 assert(type() == ThreadSafepointState::_running,
1071 "polling page exception on thread not running state");
1072
1073 // Step 1: Find the nmethod from the return address
1074 if (ShowSafepointMsgs && Verbose) {
1075 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
1076 }
1077 address real_return_addr = thread()->saved_exception_pc();
1078
1079 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1080 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1081 CompiledMethod* nm = (CompiledMethod*)cb;
1082
1083 // Find frame of caller
1084 frame stub_fr = thread()->last_frame();
1085 CodeBlob* stub_cb = stub_fr.cb();
1086 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1087 RegisterMap map(thread(), true);
1088 frame caller_fr = stub_fr.sender(&map);
1089
1090 // Should only be poll_return or poll
1091 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1092
1093 // This is a poll immediately before a return. The exception handling code
1094 // has already had the effect of causing the return to occur, so the execution
1095 // will continue immediately after the call. In addition, the oopmap at the
1096 // return point does not mark the return value as an oop (if it is), so
1097 // it needs a handle here to be updated.
1098 if( nm->is_at_poll_return(real_return_addr) ) {
1099 // See if return type is an oop.
1100 bool return_oop = nm->method()->is_returning_oop();
1101 Handle return_value;
1102 if (return_oop) {
1103 // The oop result has been saved on the stack together with all
1104 // the other registers. In order to preserve it over GCs we need
1105 // to keep it in a handle.
1106 oop result = caller_fr.saved_oop_result(&map);
1107 assert(oopDesc::is_oop_or_null(result), "must be oop");
1108 return_value = Handle(thread(), result);
1109 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1110 }
1111
1112 // Block the thread
1113 SafepointSynchronize::block(thread());
1114
1115 // restore oop result, if any
1116 if (return_oop) {
1117 caller_fr.set_saved_oop_result(&map, return_value());
1118 }
1119 }
1120
1121 // This is a safepoint poll. Verify the return address and block.
1122 else {
1123 set_at_poll_safepoint(true);
1124
1125 // verify the blob built the "return address" correctly
1126 assert(real_return_addr == caller_fr.pc(), "must match");
1127
1128 // Block the thread
1129 SafepointSynchronize::block(thread());
1130 set_at_poll_safepoint(false);
1131
1132 // If we have a pending async exception deoptimize the frame
1133 // as otherwise we may never deliver it.
1134 if (thread()->has_async_condition()) {
1135 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1136 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1137 }
1138
1139 // If an exception has been installed we must check for a pending deoptimization
1140 // Deoptimize frame if exception has been thrown.
1141
1142 if (thread()->has_pending_exception() ) {
1143 RegisterMap map(thread(), true);
1144 frame caller_fr = stub_fr.sender(&map);
1145 if (caller_fr.is_deoptimized_frame()) {
1146 // The exception patch will destroy registers that are still
1147 // live and will be needed during deoptimization. Defer the
1148 // Async exception should have deferred the exception until the
1149 // next safepoint which will be detected when we get into
1150 // the interpreter so if we have an exception now things
1151 // are messed up.
1152
1153 fatal("Exception installed and deoptimization is pending");
1154 }
1155 }
1156 }
1157 }
1158
1159
1160 //
1161 // Statistics & Instrumentations
1162 //
1163 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1164 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1165 int SafepointSynchronize::_cur_stat_index = 0;
1166 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1167 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1168 jlong SafepointSynchronize::_max_sync_time = 0;
1169 jlong SafepointSynchronize::_max_vmop_time = 0;
1170 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1171
1172 static jlong cleanup_end_time = 0;
1173 static bool need_to_track_page_armed_status = false;
1174 static bool init_done = false;
1175
1176 // Helper method to print the header.
1177 static void print_header() {
1178 // The number of spaces is significant here, and should match the format
1179 // specifiers in print_statistics().
1180
1181 tty->print(" vmop "
1182 "[ threads: total initially_running wait_to_block ]"
1183 "[ time: spin block sync cleanup vmop ] ");
1184
1185 // no page armed status printed out if it is always armed.
1186 if (need_to_track_page_armed_status) {
1187 tty->print("page_armed ");
1188 }
1189
1190 tty->print_cr("page_trap_count");
1191 }
1192
1193 void SafepointSynchronize::deferred_initialize_stat() {
1194 if (init_done) return;
1195
1196 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1197 // be printed right away, in which case, _safepoint_stats will regress to
1198 // a single element array. Otherwise, it is a circular ring buffer with default
1199 // size of PrintSafepointStatisticsCount.
1200 int stats_array_size;
1201 if (PrintSafepointStatisticsTimeout > 0) {
1202 stats_array_size = 1;
1203 PrintSafepointStatistics = true;
1204 } else {
1205 stats_array_size = PrintSafepointStatisticsCount;
1206 }
1207 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1208 * sizeof(SafepointStats), mtInternal);
1209 guarantee(_safepoint_stats != NULL,
1210 "not enough memory for safepoint instrumentation data");
1211
1212 if (DeferPollingPageLoopCount >= 0) {
1213 need_to_track_page_armed_status = true;
1214 }
1215 init_done = true;
1216 }
1217
1218 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1219 assert(init_done, "safepoint statistics array hasn't been initialized");
1220 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1221
1222 spstat->_time_stamp = _ts_of_current_safepoint;
1223
1224 VM_Operation *op = VMThread::vm_operation();
1225 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1226 if (op != NULL) {
1227 _safepoint_reasons[spstat->_vmop_type]++;
1228 }
1229
1230 spstat->_nof_total_threads = nof_threads;
1231 spstat->_nof_initial_running_threads = nof_running;
1232 spstat->_nof_threads_hit_page_trap = 0;
1233
1234 // Records the start time of spinning. The real time spent on spinning
1235 // will be adjusted when spin is done. Same trick is applied for time
1236 // spent on waiting for threads to block.
1237 if (nof_running != 0) {
1238 spstat->_time_to_spin = os::javaTimeNanos();
1239 } else {
1240 spstat->_time_to_spin = 0;
1241 }
1242 }
1243
1244 void SafepointSynchronize::update_statistics_on_spin_end() {
1245 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1246
1247 jlong cur_time = os::javaTimeNanos();
1248
1249 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1250 if (spstat->_nof_initial_running_threads != 0) {
1251 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1252 }
1253
1254 if (need_to_track_page_armed_status) {
1255 spstat->_page_armed = (PageArmed == 1);
1256 }
1257
1258 // Records the start time of waiting for to block. Updated when block is done.
1259 if (_waiting_to_block != 0) {
1260 spstat->_time_to_wait_to_block = cur_time;
1261 } else {
1262 spstat->_time_to_wait_to_block = 0;
1263 }
1264 }
1265
1266 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1267 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1268
1269 if (spstat->_nof_threads_wait_to_block != 0) {
1270 spstat->_time_to_wait_to_block = end_time -
1271 spstat->_time_to_wait_to_block;
1272 }
1273
1274 // Records the end time of sync which will be used to calculate the total
1275 // vm operation time. Again, the real time spending in syncing will be deducted
1276 // from the start of the sync time later when end_statistics is called.
1277 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1278 if (spstat->_time_to_sync > _max_sync_time) {
1279 _max_sync_time = spstat->_time_to_sync;
1280 }
1281
1282 spstat->_time_to_do_cleanups = end_time;
1283 }
1284
1285 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1286 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1287
1288 // Record how long spent in cleanup tasks.
1289 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1290
1291 cleanup_end_time = end_time;
1292 }
1293
1294 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1295 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1296
1297 // Update the vm operation time.
1298 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1299 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1300 _max_vmop_time = spstat->_time_to_exec_vmop;
1301 }
1302 // Only the sync time longer than the specified
1303 // PrintSafepointStatisticsTimeout will be printed out right away.
1304 // By default, it is -1 meaning all samples will be put into the list.
1305 if ( PrintSafepointStatisticsTimeout > 0) {
1306 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1307 print_statistics();
1308 }
1309 } else {
1310 // The safepoint statistics will be printed out when the _safepoin_stats
1311 // array fills up.
1312 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1313 print_statistics();
1314 _cur_stat_index = 0;
1315 } else {
1316 _cur_stat_index++;
1317 }
1318 }
1319 }
1320
1321 void SafepointSynchronize::print_statistics() {
1322 for (int index = 0; index <= _cur_stat_index; index++) {
1323 if (index % 30 == 0) {
1324 print_header();
1325 }
1326 SafepointStats* sstats = &_safepoint_stats[index];
1327 tty->print("%8.3f: ", sstats->_time_stamp);
1328 tty->print("%-30s [ "
1329 INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " "
1330 "]",
1331 (sstats->_vmop_type == -1 ? "no vm operation" : VM_Operation::name(sstats->_vmop_type)),
1332 sstats->_nof_total_threads,
1333 sstats->_nof_initial_running_threads,
1334 sstats->_nof_threads_wait_to_block);
1335 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1336 tty->print("[ "
1337 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1338 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1339 INT64_FORMAT_W(7) " ] ",
1340 (int64_t)(sstats->_time_to_spin / MICROUNITS),
1341 (int64_t)(sstats->_time_to_wait_to_block / MICROUNITS),
1342 (int64_t)(sstats->_time_to_sync / MICROUNITS),
1343 (int64_t)(sstats->_time_to_do_cleanups / MICROUNITS),
1344 (int64_t)(sstats->_time_to_exec_vmop / MICROUNITS));
1345
1346 if (need_to_track_page_armed_status) {
1347 tty->print(INT32_FORMAT_W(10) " ", sstats->_page_armed);
1348 }
1349 tty->print_cr(INT32_FORMAT_W(15) " ", sstats->_nof_threads_hit_page_trap);
1350 }
1351 }
1352
1353 // This method will be called when VM exits. It will first call
1354 // print_statistics to print out the rest of the sampling. Then
1355 // it tries to summarize the sampling.
1356 void SafepointSynchronize::print_stat_on_exit() {
1357 if (_safepoint_stats == NULL) return;
1358
1359 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1360
1361 // During VM exit, end_statistics may not get called and in that
1362 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1363 // don't print it out.
1364 // Approximate the vm op time.
1365 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1366 os::javaTimeNanos() - cleanup_end_time;
1367
1368 if ( PrintSafepointStatisticsTimeout < 0 ||
1369 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1370 print_statistics();
1371 }
1372 tty->cr();
1373
1374 // Print out polling page sampling status.
1375 if (!need_to_track_page_armed_status) {
1376 tty->print_cr("Polling page always armed");
1377 } else {
1378 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
1379 DeferPollingPageLoopCount);
1380 }
1381
1382 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1383 if (_safepoint_reasons[index] != 0) {
1384 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1385 _safepoint_reasons[index]);
1386 }
1387 }
1388
1389 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1390 _coalesced_vmop_count);
1391 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1392 (int64_t)(_max_sync_time / MICROUNITS));
1393 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1394 INT64_FORMAT_W(5) " ms",
1395 (int64_t)(_max_vmop_time / MICROUNITS));
1396 }
1397
1398 // ------------------------------------------------------------------------------------------------
1399 // Non-product code
1400
1401 #ifndef PRODUCT
1402
1403 void SafepointSynchronize::print_state() {
1404 if (_state == _not_synchronized) {
1405 tty->print_cr("not synchronized");
1406 } else if (_state == _synchronizing || _state == _synchronized) {
1407 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1408 "synchronized");
1409
1410 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1411 cur->safepoint_state()->print();
1412 }
1413 }
1414 }
1415
1416 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1417 if (ShowSafepointMsgs) {
1418 va_list ap;
1419 va_start(ap, format);
1420 tty->vprint_cr(format, ap);
1421 va_end(ap);
1422 }
1423 }
1424
1425 #endif // !PRODUCT