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 (int64_t)((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 there are many monitors to deflate.
529 if (ObjectSynchronizer::is_cleanup_needed()) return true;
530 // Need a safepoint if some inline cache buffers is non-empty
531 if (!InlineCacheBuffer::is_empty()) return true;
532 return false;
533 }
534
535 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) {
536 if (event.should_commit()) {
537 event.set_safepointId(SafepointSynchronize::safepoint_counter());
538 event.set_name(name);
539 event.commit();
540 }
541 }
542
543 class ParallelSPCleanupThreadClosure : public ThreadClosure {
544 private:
545 CodeBlobClosure* _nmethod_cl;
546 DeflateMonitorCounters* _counters;
547
548 public:
549 ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) :
550 _counters(counters),
551 _nmethod_cl(NMethodSweeper::prepare_mark_active_nmethods()) {}
552
553 void do_thread(Thread* thread) {
554 ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters);
555 if (_nmethod_cl != NULL && thread->is_Java_thread() &&
556 ! thread->is_Code_cache_sweeper_thread()) {
557 JavaThread* jt = (JavaThread*) thread;
558 jt->nmethods_do(_nmethod_cl);
559 }
560 }
561 };
562
563 class ParallelSPCleanupTask : public AbstractGangTask {
564 private:
565 SubTasksDone _subtasks;
566 ParallelSPCleanupThreadClosure _cleanup_threads_cl;
567 uint _num_workers;
568 DeflateMonitorCounters* _counters;
569 public:
570 ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
571 AbstractGangTask("Parallel Safepoint Cleanup"),
572 _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
573 _num_workers(num_workers),
574 _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)),
575 _counters(counters) {}
576
577 void work(uint worker_id) {
578 // All threads deflate monitors and mark nmethods (if necessary).
579 Threads::parallel_java_threads_do(&_cleanup_threads_cl);
580
581 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
582 const char* name = "deflating idle monitors";
583 EventSafepointCleanupTask event;
584 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
585 ObjectSynchronizer::deflate_idle_monitors(_counters);
586 event_safepoint_cleanup_task_commit(event, name);
587 }
588
589 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
590 const char* name = "updating inline caches";
591 EventSafepointCleanupTask event;
592 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
593 InlineCacheBuffer::update_inline_caches();
594 event_safepoint_cleanup_task_commit(event, name);
595 }
596
597 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
598 const char* name = "compilation policy safepoint handler";
599 EventSafepointCleanupTask event;
600 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
601 CompilationPolicy::policy()->do_safepoint_work();
602 event_safepoint_cleanup_task_commit(event, name);
603 }
604
605 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
606 if (SymbolTable::needs_rehashing()) {
607 const char* name = "rehashing symbol table";
608 EventSafepointCleanupTask event;
609 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
610 SymbolTable::rehash_table();
611 event_safepoint_cleanup_task_commit(event, name);
612 }
613 }
614
615 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
616 if (StringTable::needs_rehashing()) {
617 const char* name = "rehashing string table";
618 EventSafepointCleanupTask event;
619 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
620 StringTable::rehash_table();
621 event_safepoint_cleanup_task_commit(event, name);
622 }
623 }
624
625 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) {
626 // CMS delays purging the CLDG until the beginning of the next safepoint and to
627 // make sure concurrent sweep is done
628 const char* name = "purging class loader data graph";
629 EventSafepointCleanupTask event;
630 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
631 ClassLoaderDataGraph::purge_if_needed();
632 event_safepoint_cleanup_task_commit(event, name);
633 }
634 _subtasks.all_tasks_completed(_num_workers);
635 }
636 };
637
638 // Various cleaning tasks that should be done periodically at safepoints.
639 void SafepointSynchronize::do_cleanup_tasks() {
640
641 TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup));
642
643 // Prepare for monitor deflation.
644 DeflateMonitorCounters deflate_counters;
645 ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
646
647 CollectedHeap* heap = Universe::heap();
648 assert(heap != NULL, "heap not initialized yet?");
649 WorkGang* cleanup_workers = heap->get_safepoint_workers();
650 if (cleanup_workers != NULL) {
651 // Parallel cleanup using GC provided thread pool.
652 uint num_cleanup_workers = cleanup_workers->active_workers();
653 ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
654 StrongRootsScope srs(num_cleanup_workers);
655 cleanup_workers->run_task(&cleanup);
656 } else {
657 // Serial cleanup using VMThread.
658 ParallelSPCleanupTask cleanup(1, &deflate_counters);
659 StrongRootsScope srs(1);
660 cleanup.work(0);
661 }
662
663 // Finish monitor deflation.
664 ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
665 }
666
667
668 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
669 switch(state) {
670 case _thread_in_native:
671 // native threads are safe if they have no java stack or have walkable stack
672 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
673
674 // blocked threads should have already have walkable stack
675 case _thread_blocked:
676 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
677 return true;
678
679 default:
680 return false;
681 }
682 }
683
684
685 // See if the thread is running inside a lazy critical native and
686 // update the thread critical count if so. Also set a suspend flag to
687 // cause the native wrapper to return into the JVM to do the unlock
688 // once the native finishes.
689 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
690 if (state == _thread_in_native &&
691 thread->has_last_Java_frame() &&
692 thread->frame_anchor()->walkable()) {
693 // This thread might be in a critical native nmethod so look at
694 // the top of the stack and increment the critical count if it
695 // is.
696 frame wrapper_frame = thread->last_frame();
697 CodeBlob* stub_cb = wrapper_frame.cb();
698 if (stub_cb != NULL &&
699 stub_cb->is_nmethod() &&
700 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
701 // A thread could potentially be in a critical native across
702 // more than one safepoint, so only update the critical state on
703 // the first one. When it returns it will perform the unlock.
704 if (!thread->do_critical_native_unlock()) {
705 #ifdef ASSERT
706 if (!thread->in_critical()) {
707 GCLocker::increment_debug_jni_lock_count();
708 }
709 #endif
710 thread->enter_critical();
711 // Make sure the native wrapper calls back on return to
712 // perform the needed critical unlock.
713 thread->set_critical_native_unlock();
714 }
715 }
716 }
717 }
718
719
720
721 // -------------------------------------------------------------------------------------------------------
722 // Implementation of Safepoint callback point
723
724 void SafepointSynchronize::block(JavaThread *thread) {
725 assert(thread != NULL, "thread must be set");
726 assert(thread->is_Java_thread(), "not a Java thread");
727
728 // Threads shouldn't block if they are in the middle of printing, but...
729 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
730
731 // Only bail from the block() call if the thread is gone from the
732 // thread list; starting to exit should still block.
733 if (thread->is_terminated()) {
734 // block current thread if we come here from native code when VM is gone
735 thread->block_if_vm_exited();
736
737 // otherwise do nothing
738 return;
739 }
740
741 JavaThreadState state = thread->thread_state();
742 thread->frame_anchor()->make_walkable(thread);
743
744 // Check that we have a valid thread_state at this point
745 switch(state) {
746 case _thread_in_vm_trans:
747 case _thread_in_Java: // From compiled code
748
749 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
750 // we pretend we are still in the VM.
751 thread->set_thread_state(_thread_in_vm);
752
753 if (is_synchronizing()) {
754 Atomic::inc (&TryingToBlock) ;
755 }
756
757 // We will always be holding the Safepoint_lock when we are examine the state
758 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
759 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
760 Safepoint_lock->lock_without_safepoint_check();
761 if (is_synchronizing()) {
762 // Decrement the number of threads to wait for and signal vm thread
763 assert(_waiting_to_block > 0, "sanity check");
764 _waiting_to_block--;
765 thread->safepoint_state()->set_has_called_back(true);
766
767 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
768 if (thread->in_critical()) {
769 // Notice that this thread is in a critical section
770 increment_jni_active_count();
771 }
772
773 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
774 if (_waiting_to_block == 0) {
775 Safepoint_lock->notify_all();
776 }
777 }
778
779 // We transition the thread to state _thread_blocked here, but
780 // we can't do our usual check for external suspension and then
781 // self-suspend after the lock_without_safepoint_check() call
782 // below because we are often called during transitions while
783 // we hold different locks. That would leave us suspended while
784 // holding a resource which results in deadlocks.
785 thread->set_thread_state(_thread_blocked);
786 Safepoint_lock->unlock();
787
788 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
789 // the entire safepoint, the threads will all line up here during the safepoint.
790 Threads_lock->lock_without_safepoint_check();
791 // restore original state. This is important if the thread comes from compiled code, so it
792 // will continue to execute with the _thread_in_Java state.
793 thread->set_thread_state(state);
794 Threads_lock->unlock();
795 break;
796
797 case _thread_in_native_trans:
798 case _thread_blocked_trans:
799 case _thread_new_trans:
800 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
801 thread->print_thread_state();
802 fatal("Deadlock in safepoint code. "
803 "Should have called back to the VM before blocking.");
804 }
805
806 // We transition the thread to state _thread_blocked here, but
807 // we can't do our usual check for external suspension and then
808 // self-suspend after the lock_without_safepoint_check() call
809 // below because we are often called during transitions while
810 // we hold different locks. That would leave us suspended while
811 // holding a resource which results in deadlocks.
812 thread->set_thread_state(_thread_blocked);
813
814 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
815 // the safepoint code might still be waiting for it to block. We need to change the state here,
816 // so it can see that it is at a safepoint.
817
818 // Block until the safepoint operation is completed.
819 Threads_lock->lock_without_safepoint_check();
820
821 // Restore state
822 thread->set_thread_state(state);
823
824 Threads_lock->unlock();
825 break;
826
827 default:
828 fatal("Illegal threadstate encountered: %d", state);
829 }
830
831 // Check for pending. async. exceptions or suspends - except if the
832 // thread was blocked inside the VM. has_special_runtime_exit_condition()
833 // is called last since it grabs a lock and we only want to do that when
834 // we must.
835 //
836 // Note: we never deliver an async exception at a polling point as the
837 // compiler may not have an exception handler for it. The polling
838 // code will notice the async and deoptimize and the exception will
839 // be delivered. (Polling at a return point is ok though). Sure is
840 // a lot of bother for a deprecated feature...
841 //
842 // We don't deliver an async exception if the thread state is
843 // _thread_in_native_trans so JNI functions won't be called with
844 // a surprising pending exception. If the thread state is going back to java,
845 // async exception is checked in check_special_condition_for_native_trans().
846
847 if (state != _thread_blocked_trans &&
848 state != _thread_in_vm_trans &&
849 thread->has_special_runtime_exit_condition()) {
850 thread->handle_special_runtime_exit_condition(
851 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
852 }
853 }
854
855 // ------------------------------------------------------------------------------------------------------
856 // Exception handlers
857
858
859 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
860 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
861 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
862 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
863
864 if (ShowSafepointMsgs) {
865 tty->print("handle_polling_page_exception: ");
866 }
867
868 if (PrintSafepointStatistics) {
869 inc_page_trap_count();
870 }
871
872 ThreadSafepointState* state = thread->safepoint_state();
873
874 state->handle_polling_page_exception();
875 }
876
877
878 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
879 if (!timeout_error_printed) {
880 timeout_error_printed = true;
881 // Print out the thread info which didn't reach the safepoint for debugging
882 // purposes (useful when there are lots of threads in the debugger).
883 tty->cr();
884 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
885 if (reason == _spinning_timeout) {
886 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
887 } else if (reason == _blocking_timeout) {
888 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
889 }
890
891 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
892 ThreadSafepointState *cur_state;
893 ResourceMark rm;
894 for(JavaThread *cur_thread = Threads::first(); cur_thread;
895 cur_thread = cur_thread->next()) {
896 cur_state = cur_thread->safepoint_state();
897
898 if (cur_thread->thread_state() != _thread_blocked &&
899 ((reason == _spinning_timeout && cur_state->is_running()) ||
900 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
901 tty->print("# ");
902 cur_thread->print();
903 tty->cr();
904 }
905 }
906 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
907 }
908
909 // To debug the long safepoint, specify both DieOnSafepointTimeout &
910 // ShowMessageBoxOnError.
911 if (DieOnSafepointTimeout) {
912 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
913 SafepointTimeoutDelay, VMThread::vm_safepoint_description());
914 }
915 }
916
917
918 // -------------------------------------------------------------------------------------------------------
919 // Implementation of ThreadSafepointState
920
921 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
922 _thread = thread;
923 _type = _running;
924 _has_called_back = false;
925 _at_poll_safepoint = false;
926 }
927
928 void ThreadSafepointState::create(JavaThread *thread) {
929 ThreadSafepointState *state = new ThreadSafepointState(thread);
930 thread->set_safepoint_state(state);
931 }
932
933 void ThreadSafepointState::destroy(JavaThread *thread) {
934 if (thread->safepoint_state()) {
935 delete(thread->safepoint_state());
936 thread->set_safepoint_state(NULL);
937 }
938 }
939
940 void ThreadSafepointState::examine_state_of_thread() {
941 assert(is_running(), "better be running or just have hit safepoint poll");
942
943 JavaThreadState state = _thread->thread_state();
944
945 // Save the state at the start of safepoint processing.
946 _orig_thread_state = state;
947
948 // Check for a thread that is suspended. Note that thread resume tries
949 // to grab the Threads_lock which we own here, so a thread cannot be
950 // resumed during safepoint synchronization.
951
952 // We check to see if this thread is suspended without locking to
953 // avoid deadlocking with a third thread that is waiting for this
954 // thread to be suspended. The third thread can notice the safepoint
955 // that we're trying to start at the beginning of its SR_lock->wait()
956 // call. If that happens, then the third thread will block on the
957 // safepoint while still holding the underlying SR_lock. We won't be
958 // able to get the SR_lock and we'll deadlock.
959 //
960 // We don't need to grab the SR_lock here for two reasons:
961 // 1) The suspend flags are both volatile and are set with an
962 // Atomic::cmpxchg() call so we should see the suspended
963 // state right away.
964 // 2) We're being called from the safepoint polling loop; if
965 // we don't see the suspended state on this iteration, then
966 // we'll come around again.
967 //
968 bool is_suspended = _thread->is_ext_suspended();
969 if (is_suspended) {
970 roll_forward(_at_safepoint);
971 return;
972 }
973
974 // Some JavaThread states have an initial safepoint state of
975 // running, but are actually at a safepoint. We will happily
976 // agree and update the safepoint state here.
977 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
978 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
979 roll_forward(_at_safepoint);
980 return;
981 }
982
983 if (state == _thread_in_vm) {
984 roll_forward(_call_back);
985 return;
986 }
987
988 // All other thread states will continue to run until they
989 // transition and self-block in state _blocked
990 // Safepoint polling in compiled code causes the Java threads to do the same.
991 // Note: new threads may require a malloc so they must be allowed to finish
992
993 assert(is_running(), "examine_state_of_thread on non-running thread");
994 return;
995 }
996
997 // Returns true is thread could not be rolled forward at present position.
998 void ThreadSafepointState::roll_forward(suspend_type type) {
999 _type = type;
1000
1001 switch(_type) {
1002 case _at_safepoint:
1003 SafepointSynchronize::signal_thread_at_safepoint();
1004 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
1005 if (_thread->in_critical()) {
1006 // Notice that this thread is in a critical section
1007 SafepointSynchronize::increment_jni_active_count();
1008 }
1009 break;
1010
1011 case _call_back:
1012 set_has_called_back(false);
1013 break;
1014
1015 case _running:
1016 default:
1017 ShouldNotReachHere();
1018 }
1019 }
1020
1021 void ThreadSafepointState::restart() {
1022 switch(type()) {
1023 case _at_safepoint:
1024 case _call_back:
1025 break;
1026
1027 case _running:
1028 default:
1029 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
1030 p2i(_thread), _type);
1031 _thread->print();
1032 ShouldNotReachHere();
1033 }
1034 _type = _running;
1035 set_has_called_back(false);
1036 }
1037
1038
1039 void ThreadSafepointState::print_on(outputStream *st) const {
1040 const char *s = NULL;
1041
1042 switch(_type) {
1043 case _running : s = "_running"; break;
1044 case _at_safepoint : s = "_at_safepoint"; break;
1045 case _call_back : s = "_call_back"; break;
1046 default:
1047 ShouldNotReachHere();
1048 }
1049
1050 st->print_cr("Thread: " INTPTR_FORMAT
1051 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1052 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
1053 _at_poll_safepoint);
1054
1055 _thread->print_thread_state_on(st);
1056 }
1057
1058 // ---------------------------------------------------------------------------------------------------------------------
1059
1060 // Block the thread at the safepoint poll or poll return.
1061 void ThreadSafepointState::handle_polling_page_exception() {
1062
1063 // Check state. block() will set thread state to thread_in_vm which will
1064 // cause the safepoint state _type to become _call_back.
1065 assert(type() == ThreadSafepointState::_running,
1066 "polling page exception on thread not running state");
1067
1068 // Step 1: Find the nmethod from the return address
1069 if (ShowSafepointMsgs && Verbose) {
1070 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
1071 }
1072 address real_return_addr = thread()->saved_exception_pc();
1073
1074 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1075 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1076 CompiledMethod* nm = (CompiledMethod*)cb;
1077
1078 // Find frame of caller
1079 frame stub_fr = thread()->last_frame();
1080 CodeBlob* stub_cb = stub_fr.cb();
1081 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1082 RegisterMap map(thread(), true);
1083 frame caller_fr = stub_fr.sender(&map);
1084
1085 // Should only be poll_return or poll
1086 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1087
1088 // This is a poll immediately before a return. The exception handling code
1089 // has already had the effect of causing the return to occur, so the execution
1090 // will continue immediately after the call. In addition, the oopmap at the
1091 // return point does not mark the return value as an oop (if it is), so
1092 // it needs a handle here to be updated.
1093 if( nm->is_at_poll_return(real_return_addr) ) {
1094 // See if return type is an oop.
1095 bool return_oop = nm->method()->is_returning_oop();
1096 Handle return_value;
1097 if (return_oop) {
1098 // The oop result has been saved on the stack together with all
1099 // the other registers. In order to preserve it over GCs we need
1100 // to keep it in a handle.
1101 oop result = caller_fr.saved_oop_result(&map);
1102 assert(result == NULL || result->is_oop(), "must be oop");
1103 return_value = Handle(thread(), result);
1104 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1105 }
1106
1107 // Block the thread
1108 SafepointSynchronize::block(thread());
1109
1110 // restore oop result, if any
1111 if (return_oop) {
1112 caller_fr.set_saved_oop_result(&map, return_value());
1113 }
1114 }
1115
1116 // This is a safepoint poll. Verify the return address and block.
1117 else {
1118 set_at_poll_safepoint(true);
1119
1120 // verify the blob built the "return address" correctly
1121 assert(real_return_addr == caller_fr.pc(), "must match");
1122
1123 // Block the thread
1124 SafepointSynchronize::block(thread());
1125 set_at_poll_safepoint(false);
1126
1127 // If we have a pending async exception deoptimize the frame
1128 // as otherwise we may never deliver it.
1129 if (thread()->has_async_condition()) {
1130 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1131 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1132 }
1133
1134 // If an exception has been installed we must check for a pending deoptimization
1135 // Deoptimize frame if exception has been thrown.
1136
1137 if (thread()->has_pending_exception() ) {
1138 RegisterMap map(thread(), true);
1139 frame caller_fr = stub_fr.sender(&map);
1140 if (caller_fr.is_deoptimized_frame()) {
1141 // The exception patch will destroy registers that are still
1142 // live and will be needed during deoptimization. Defer the
1143 // Async exception should have deferred the exception until the
1144 // next safepoint which will be detected when we get into
1145 // the interpreter so if we have an exception now things
1146 // are messed up.
1147
1148 fatal("Exception installed and deoptimization is pending");
1149 }
1150 }
1151 }
1152 }
1153
1154
1155 //
1156 // Statistics & Instrumentations
1157 //
1158 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1159 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1160 int SafepointSynchronize::_cur_stat_index = 0;
1161 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1162 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1163 jlong SafepointSynchronize::_max_sync_time = 0;
1164 jlong SafepointSynchronize::_max_vmop_time = 0;
1165 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1166
1167 static jlong cleanup_end_time = 0;
1168 static bool need_to_track_page_armed_status = false;
1169 static bool init_done = false;
1170
1171 // Helper method to print the header.
1172 static void print_header() {
1173 // The number of spaces is significant here, and should match the format
1174 // specifiers in print_statistics().
1175
1176 tty->print(" vmop "
1177 "[ threads: total initially_running wait_to_block ]"
1178 "[ time: spin block sync cleanup vmop ] ");
1179
1180 // no page armed status printed out if it is always armed.
1181 if (need_to_track_page_armed_status) {
1182 tty->print("page_armed ");
1183 }
1184
1185 tty->print_cr("page_trap_count");
1186 }
1187
1188 void SafepointSynchronize::deferred_initialize_stat() {
1189 if (init_done) return;
1190
1191 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1192 // be printed right away, in which case, _safepoint_stats will regress to
1193 // a single element array. Otherwise, it is a circular ring buffer with default
1194 // size of PrintSafepointStatisticsCount.
1195 int stats_array_size;
1196 if (PrintSafepointStatisticsTimeout > 0) {
1197 stats_array_size = 1;
1198 PrintSafepointStatistics = true;
1199 } else {
1200 stats_array_size = PrintSafepointStatisticsCount;
1201 }
1202 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1203 * sizeof(SafepointStats), mtInternal);
1204 guarantee(_safepoint_stats != NULL,
1205 "not enough memory for safepoint instrumentation data");
1206
1207 if (DeferPollingPageLoopCount >= 0) {
1208 need_to_track_page_armed_status = true;
1209 }
1210 init_done = true;
1211 }
1212
1213 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1214 assert(init_done, "safepoint statistics array hasn't been initialized");
1215 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1216
1217 spstat->_time_stamp = _ts_of_current_safepoint;
1218
1219 VM_Operation *op = VMThread::vm_operation();
1220 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1221 if (op != NULL) {
1222 _safepoint_reasons[spstat->_vmop_type]++;
1223 }
1224
1225 spstat->_nof_total_threads = nof_threads;
1226 spstat->_nof_initial_running_threads = nof_running;
1227 spstat->_nof_threads_hit_page_trap = 0;
1228
1229 // Records the start time of spinning. The real time spent on spinning
1230 // will be adjusted when spin is done. Same trick is applied for time
1231 // spent on waiting for threads to block.
1232 if (nof_running != 0) {
1233 spstat->_time_to_spin = os::javaTimeNanos();
1234 } else {
1235 spstat->_time_to_spin = 0;
1236 }
1237 }
1238
1239 void SafepointSynchronize::update_statistics_on_spin_end() {
1240 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1241
1242 jlong cur_time = os::javaTimeNanos();
1243
1244 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1245 if (spstat->_nof_initial_running_threads != 0) {
1246 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1247 }
1248
1249 if (need_to_track_page_armed_status) {
1250 spstat->_page_armed = (PageArmed == 1);
1251 }
1252
1253 // Records the start time of waiting for to block. Updated when block is done.
1254 if (_waiting_to_block != 0) {
1255 spstat->_time_to_wait_to_block = cur_time;
1256 } else {
1257 spstat->_time_to_wait_to_block = 0;
1258 }
1259 }
1260
1261 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1262 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1263
1264 if (spstat->_nof_threads_wait_to_block != 0) {
1265 spstat->_time_to_wait_to_block = end_time -
1266 spstat->_time_to_wait_to_block;
1267 }
1268
1269 // Records the end time of sync which will be used to calculate the total
1270 // vm operation time. Again, the real time spending in syncing will be deducted
1271 // from the start of the sync time later when end_statistics is called.
1272 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1273 if (spstat->_time_to_sync > _max_sync_time) {
1274 _max_sync_time = spstat->_time_to_sync;
1275 }
1276
1277 spstat->_time_to_do_cleanups = end_time;
1278 }
1279
1280 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1281 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1282
1283 // Record how long spent in cleanup tasks.
1284 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1285
1286 cleanup_end_time = end_time;
1287 }
1288
1289 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1290 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1291
1292 // Update the vm operation time.
1293 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1294 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1295 _max_vmop_time = spstat->_time_to_exec_vmop;
1296 }
1297 // Only the sync time longer than the specified
1298 // PrintSafepointStatisticsTimeout will be printed out right away.
1299 // By default, it is -1 meaning all samples will be put into the list.
1300 if ( PrintSafepointStatisticsTimeout > 0) {
1301 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1302 print_statistics();
1303 }
1304 } else {
1305 // The safepoint statistics will be printed out when the _safepoin_stats
1306 // array fills up.
1307 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1308 print_statistics();
1309 _cur_stat_index = 0;
1310 } else {
1311 _cur_stat_index++;
1312 }
1313 }
1314 }
1315
1316 void SafepointSynchronize::print_statistics() {
1317 for (int index = 0; index <= _cur_stat_index; index++) {
1318 if (index % 30 == 0) {
1319 print_header();
1320 }
1321 SafepointStats* sstats = &_safepoint_stats[index];
1322 tty->print("%8.3f: ", sstats->_time_stamp);
1323 tty->print("%-30s [ "
1324 INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " "
1325 "]",
1326 (sstats->_vmop_type == -1 ? "no vm operation" : VM_Operation::name(sstats->_vmop_type)),
1327 sstats->_nof_total_threads,
1328 sstats->_nof_initial_running_threads,
1329 sstats->_nof_threads_wait_to_block);
1330 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1331 tty->print("[ "
1332 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1333 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1334 INT64_FORMAT_W(7) " ] ",
1335 (int64_t)(sstats->_time_to_spin / MICROUNITS),
1336 (int64_t)(sstats->_time_to_wait_to_block / MICROUNITS),
1337 (int64_t)(sstats->_time_to_sync / MICROUNITS),
1338 (int64_t)(sstats->_time_to_do_cleanups / MICROUNITS),
1339 (int64_t)(sstats->_time_to_exec_vmop / MICROUNITS));
1340
1341 if (need_to_track_page_armed_status) {
1342 tty->print(INT32_FORMAT_W(10) " ", sstats->_page_armed);
1343 }
1344 tty->print_cr(INT32_FORMAT_W(15) " ", sstats->_nof_threads_hit_page_trap);
1345 }
1346 }
1347
1348 // This method will be called when VM exits. It will first call
1349 // print_statistics to print out the rest of the sampling. Then
1350 // it tries to summarize the sampling.
1351 void SafepointSynchronize::print_stat_on_exit() {
1352 if (_safepoint_stats == NULL) return;
1353
1354 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1355
1356 // During VM exit, end_statistics may not get called and in that
1357 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1358 // don't print it out.
1359 // Approximate the vm op time.
1360 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1361 os::javaTimeNanos() - cleanup_end_time;
1362
1363 if ( PrintSafepointStatisticsTimeout < 0 ||
1364 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1365 print_statistics();
1366 }
1367 tty->cr();
1368
1369 // Print out polling page sampling status.
1370 if (!need_to_track_page_armed_status) {
1371 tty->print_cr("Polling page always armed");
1372 } else {
1373 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
1374 DeferPollingPageLoopCount);
1375 }
1376
1377 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1378 if (_safepoint_reasons[index] != 0) {
1379 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1380 _safepoint_reasons[index]);
1381 }
1382 }
1383
1384 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1385 _coalesced_vmop_count);
1386 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1387 (int64_t)(_max_sync_time / MICROUNITS));
1388 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1389 INT64_FORMAT_W(5) " ms",
1390 (int64_t)(_max_vmop_time / MICROUNITS));
1391 }
1392
1393 // ------------------------------------------------------------------------------------------------
1394 // Non-product code
1395
1396 #ifndef PRODUCT
1397
1398 void SafepointSynchronize::print_state() {
1399 if (_state == _not_synchronized) {
1400 tty->print_cr("not synchronized");
1401 } else if (_state == _synchronizing || _state == _synchronized) {
1402 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1403 "synchronized");
1404
1405 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1406 cur->safepoint_state()->print();
1407 }
1408 }
1409 }
1410
1411 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1412 if (ShowSafepointMsgs) {
1413 va_list ap;
1414 va_start(ap, format);
1415 tty->vprint_cr(format, ap);
1416 va_end(ap);
1417 }
1418 }
1419
1420 #endif // !PRODUCT