1 /*
2 * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/stringTable.hpp"
27 #include "classfile/symbolTable.hpp"
28 #include "classfile/systemDictionary.hpp"
29 #include "code/codeCache.hpp"
30 #include "code/icBuffer.hpp"
31 #include "code/nmethod.hpp"
32 #include "code/pcDesc.hpp"
33 #include "code/scopeDesc.hpp"
34 #include "gc/shared/collectedHeap.hpp"
35 #include "gc/shared/gcLocker.inline.hpp"
36 #include "interpreter/interpreter.hpp"
37 #include "logging/log.hpp"
38 #include "memory/resourceArea.hpp"
39 #include "memory/universe.inline.hpp"
40 #include "oops/oop.inline.hpp"
41 #include "oops/symbol.hpp"
42 #include "runtime/atomic.hpp"
43 #include "runtime/compilationPolicy.hpp"
44 #include "runtime/deoptimization.hpp"
45 #include "runtime/frame.inline.hpp"
46 #include "runtime/interfaceSupport.hpp"
47 #include "runtime/mutexLocker.hpp"
48 #include "runtime/orderAccess.inline.hpp"
49 #include "runtime/osThread.hpp"
50 #include "runtime/safepoint.hpp"
51 #include "runtime/signature.hpp"
52 #include "runtime/stubCodeGenerator.hpp"
53 #include "runtime/stubRoutines.hpp"
54 #include "runtime/sweeper.hpp"
55 #include "runtime/synchronizer.hpp"
56 #include "runtime/thread.inline.hpp"
57 #include "runtime/timerTrace.hpp"
58 #include "services/runtimeService.hpp"
59 #include "trace/tracing.hpp"
60 #include "trace/traceMacros.hpp"
61 #include "utilities/events.hpp"
62 #include "utilities/macros.hpp"
63 #if INCLUDE_ALL_GCS
64 #include "gc/cms/concurrentMarkSweepThread.hpp"
65 #include "gc/g1/suspendibleThreadSet.hpp"
66 #endif // INCLUDE_ALL_GCS
67 #ifdef COMPILER1
68 #include "c1/c1_globals.hpp"
69 #endif
70
71 // --------------------------------------------------------------------------------------------------
72 // Implementation of Safepoint begin/end
73
74 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
75 volatile int SafepointSynchronize::_waiting_to_block = 0;
76 volatile int SafepointSynchronize::_safepoint_counter = 0;
77 int SafepointSynchronize::_current_jni_active_count = 0;
78 long SafepointSynchronize::_end_of_last_safepoint = 0;
79 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
80 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
81 static bool timeout_error_printed = false;
82
83 // Roll all threads forward to a safepoint and suspend them all
84 void SafepointSynchronize::begin() {
85 EventSafepointBegin begin_event;
86 Thread* myThread = Thread::current();
87 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
88
89 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
90 _safepoint_begin_time = os::javaTimeNanos();
91 _ts_of_current_safepoint = tty->time_stamp().seconds();
92 }
93
94 #if INCLUDE_ALL_GCS
95 if (UseConcMarkSweepGC) {
96 // In the future we should investigate whether CMS can use the
97 // more-general mechanism below. DLD (01/05).
98 ConcurrentMarkSweepThread::synchronize(false);
99 } else if (UseG1GC) {
100 SuspendibleThreadSet::synchronize();
101 }
102 #endif // INCLUDE_ALL_GCS
103
104 // By getting the Threads_lock, we assure that no threads are about to start or
105 // exit. It is released again in SafepointSynchronize::end().
106 Threads_lock->lock();
107
108 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
109
110 int nof_threads = Threads::number_of_threads();
111
112 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads);
113
114 RuntimeService::record_safepoint_begin();
115
116 MutexLocker mu(Safepoint_lock);
117
118 // Reset the count of active JNI critical threads
119 _current_jni_active_count = 0;
120
121 // Set number of threads to wait for, before we initiate the callbacks
122 _waiting_to_block = nof_threads;
123 TryingToBlock = 0 ;
124 int still_running = nof_threads;
125
126 // Save the starting time, so that it can be compared to see if this has taken
127 // too long to complete.
128 jlong safepoint_limit_time = 0;
129 timeout_error_printed = false;
130
131 // PrintSafepointStatisticsTimeout can be specified separately. When
132 // specified, PrintSafepointStatistics will be set to true in
133 // deferred_initialize_stat method. The initialization has to be done
134 // early enough to avoid any races. See bug 6880029 for details.
135 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
136 deferred_initialize_stat();
137 }
138
139 // Begin the process of bringing the system to a safepoint.
140 // Java threads can be in several different states and are
141 // stopped by different mechanisms:
142 //
143 // 1. Running interpreted
144 // The interpreter dispatch table is changed to force it to
145 // check for a safepoint condition between bytecodes.
146 // 2. Running in native code
147 // When returning from the native code, a Java thread must check
148 // the safepoint _state to see if we must block. If the
149 // VM thread sees a Java thread in native, it does
150 // not wait for this thread to block. The order of the memory
151 // writes and reads of both the safepoint state and the Java
152 // threads state is critical. In order to guarantee that the
153 // memory writes are serialized with respect to each other,
154 // the VM thread issues a memory barrier instruction
155 // (on MP systems). In order to avoid the overhead of issuing
156 // a memory barrier for each Java thread making native calls, each Java
157 // thread performs a write to a single memory page after changing
158 // the thread state. The VM thread performs a sequence of
159 // mprotect OS calls which forces all previous writes from all
160 // Java threads to be serialized. This is done in the
161 // os::serialize_thread_states() call. This has proven to be
162 // much more efficient than executing a membar instruction
163 // on every call to native code.
164 // 3. Running compiled Code
165 // Compiled code reads a global (Safepoint Polling) page that
166 // is set to fault if we are trying to get to a safepoint.
167 // 4. Blocked
168 // A thread which is blocked will not be allowed to return from the
169 // block condition until the safepoint operation is complete.
170 // 5. In VM or Transitioning between states
171 // If a Java thread is currently running in the VM or transitioning
172 // between states, the safepointing code will wait for the thread to
173 // block itself when it attempts transitions to a new state.
174 //
175 {
176 EventSafepointStateSynchronization sync_event;
177 int initial_running = 0;
178
179 _state = _synchronizing;
180 OrderAccess::fence();
181
182 // Flush all thread states to memory
183 if (!UseMembar) {
184 os::serialize_thread_states();
185 }
186
187 // Make interpreter safepoint aware
188 Interpreter::notice_safepoints();
189
190 if (DeferPollingPageLoopCount < 0) {
191 // Make polling safepoint aware
192 guarantee (PageArmed == 0, "invariant") ;
193 PageArmed = 1 ;
194 os::make_polling_page_unreadable();
195 }
196
197 // Consider using active_processor_count() ... but that call is expensive.
198 int ncpus = os::processor_count() ;
199
200 #ifdef ASSERT
201 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
202 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
203 // Clear the visited flag to ensure that the critical counts are collected properly.
204 cur->set_visited_for_critical_count(false);
205 }
206 #endif // ASSERT
207
208 if (SafepointTimeout)
209 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
210
211 // Iterate through all threads until it have been determined how to stop them all at a safepoint
212 unsigned int iterations = 0;
213 int steps = 0 ;
214 while(still_running > 0) {
215 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
216 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
217 ThreadSafepointState *cur_state = cur->safepoint_state();
218 if (cur_state->is_running()) {
219 cur_state->examine_state_of_thread();
220 if (!cur_state->is_running()) {
221 still_running--;
222 // consider adjusting steps downward:
223 // steps = 0
224 // steps -= NNN
225 // steps >>= 1
226 // steps = MIN(steps, 2000-100)
227 // if (iterations != 0) steps -= NNN
228 }
229 if (log_is_enabled(Trace, safepoint)) {
230 ResourceMark rm;
231 cur_state->print_on(Log(safepoint)::trace_stream());
232 }
233 }
234 }
235
236 if (iterations == 0) {
237 initial_running = still_running;
238 if (PrintSafepointStatistics) {
239 begin_statistics(nof_threads, still_running);
240 }
241 }
242
243 if (still_running > 0) {
244 // Check for if it takes to long
245 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
246 print_safepoint_timeout(_spinning_timeout);
247 }
248
249 // Spin to avoid context switching.
250 // There's a tension between allowing the mutators to run (and rendezvous)
251 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
252 // a mutator might otherwise use profitably to reach a safepoint. Excessive
253 // spinning by the VM thread on a saturated system can increase rendezvous latency.
254 // Blocking or yielding incur their own penalties in the form of context switching
255 // and the resultant loss of $ residency.
256 //
257 // Further complicating matters is that yield() does not work as naively expected
258 // on many platforms -- yield() does not guarantee that any other ready threads
259 // will run. As such we revert to naked_short_sleep() after some number of iterations.
260 // nakes_short_sleep() is implemented as a short unconditional sleep.
261 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
262 // can actually increase the time it takes the VM thread to detect that a system-wide
263 // stop-the-world safepoint has been reached. In a pathological scenario such as that
264 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
265 // In that case the mutators will be stalled waiting for the safepoint to complete and the
266 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
267 // will eventually wake up and detect that all mutators are safe, at which point
268 // we'll again make progress.
269 //
270 // Beware too that that the VMThread typically runs at elevated priority.
271 // Its default priority is higher than the default mutator priority.
272 // Obviously, this complicates spinning.
273 //
274 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
275 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
276 //
277 // See the comments in synchronizer.cpp for additional remarks on spinning.
278 //
279 // In the future we might:
280 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
281 // This is tricky as the path used by a thread exiting the JVM (say on
282 // on JNI call-out) simply stores into its state field. The burden
283 // is placed on the VM thread, which must poll (spin).
284 // 2. Find something useful to do while spinning. If the safepoint is GC-related
285 // we might aggressively scan the stacks of threads that are already safe.
286 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
287 // If all the mutators are ONPROC there's no reason to sleep or yield.
288 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
289 // 5. Check system saturation. If the system is not fully saturated then
290 // simply spin and avoid sleep/yield.
291 // 6. As still-running mutators rendezvous they could unpark the sleeping
292 // VMthread. This works well for still-running mutators that become
293 // safe. The VMthread must still poll for mutators that call-out.
294 // 7. Drive the policy on time-since-begin instead of iterations.
295 // 8. Consider making the spin duration a function of the # of CPUs:
296 // Spin = (((ncpus-1) * M) + K) + F(still_running)
297 // Alternately, instead of counting iterations of the outer loop
298 // we could count the # of threads visited in the inner loop, above.
299 // 9. On windows consider using the return value from SwitchThreadTo()
300 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
301
302 if (int(iterations) == DeferPollingPageLoopCount) {
303 guarantee (PageArmed == 0, "invariant") ;
304 PageArmed = 1 ;
305 os::make_polling_page_unreadable();
306 }
307
308 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
309 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
310 ++steps ;
311 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
312 SpinPause() ; // MP-Polite spin
313 } else
314 if (steps < DeferThrSuspendLoopCount) {
315 os::naked_yield() ;
316 } else {
317 os::naked_short_sleep(1);
318 }
319
320 iterations ++ ;
321 }
322 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
323 }
324 assert(still_running == 0, "sanity check");
325
326 if (PrintSafepointStatistics) {
327 update_statistics_on_spin_end();
328 }
329
330 if (sync_event.should_commit()) {
331 sync_event.set_safepointId(safepoint_counter());
332 sync_event.set_initialThreadCount(initial_running);
333 sync_event.set_runningThreadCount(_waiting_to_block);
334 sync_event.set_iterations(iterations);
335 sync_event.commit();
336 }
337 } //EventSafepointStateSync
338
339 // wait until all threads are stopped
340 {
341 EventSafepointWaitBlocked wait_blocked_event;
342 int initial_waiting_to_block = _waiting_to_block;
343
344 while (_waiting_to_block > 0) {
345 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
346 if (!SafepointTimeout || timeout_error_printed) {
347 Safepoint_lock->wait(true); // true, means with no safepoint checks
348 } else {
349 // Compute remaining time
350 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
351
352 // If there is no remaining time, then there is an error
353 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
354 print_safepoint_timeout(_blocking_timeout);
355 }
356 }
357 }
358 assert(_waiting_to_block == 0, "sanity check");
359
360 #ifndef PRODUCT
361 if (SafepointTimeout) {
362 jlong current_time = os::javaTimeNanos();
363 if (safepoint_limit_time < current_time) {
364 tty->print_cr("# SafepointSynchronize: Finished after "
365 INT64_FORMAT_W(6) " ms",
366 ((current_time - safepoint_limit_time) / MICROUNITS +
367 (jlong)SafepointTimeoutDelay));
368 }
369 }
370 #endif
371
372 assert((_safepoint_counter & 0x1) == 0, "must be even");
373 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
374 _safepoint_counter ++;
375
376 // Record state
377 _state = _synchronized;
378
379 OrderAccess::fence();
380
381 if (wait_blocked_event.should_commit()) {
382 wait_blocked_event.set_safepointId(safepoint_counter());
383 wait_blocked_event.set_runningThreadCount(initial_waiting_to_block);
384 wait_blocked_event.commit();
385 }
386 } // EventSafepointWaitBlocked
387
388 #ifdef ASSERT
389 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
390 // make sure all the threads were visited
391 assert(cur->was_visited_for_critical_count(), "missed a thread");
392 }
393 #endif // ASSERT
394
395 // Update the count of active JNI critical regions
396 GCLocker::set_jni_lock_count(_current_jni_active_count);
397
398 if (log_is_enabled(Debug, safepoint)) {
399 log_debug(safepoint)("Entering safepoint region: %s", VMThread::vm_safepoint_description());
400 }
401
402 RuntimeService::record_safepoint_synchronized();
403 if (PrintSafepointStatistics) {
404 update_statistics_on_sync_end(os::javaTimeNanos());
405 }
406
407 // Call stuff that needs to be run when a safepoint is just about to be completed
408 {
409 EventSafepointCleanup cleanup_event;
410 do_cleanup_tasks();
411 if (cleanup_event.should_commit()) {
412 cleanup_event.set_safepointId(safepoint_counter());
413 cleanup_event.commit();
414 }
415 }
416
417 if (PrintSafepointStatistics) {
418 // Record how much time spend on the above cleanup tasks
419 update_statistics_on_cleanup_end(os::javaTimeNanos());
420 }
421 if (begin_event.should_commit()) {
422 begin_event.set_safepointId(safepoint_counter());
423 begin_event.set_totalThreadCount(nof_threads);
424 begin_event.set_jniCriticalThreadCount(_current_jni_active_count);
425 begin_event.commit();
426 }
427 }
428
429 // Wake up all threads, so they are ready to resume execution after the safepoint
430 // operation has been carried out
431 void SafepointSynchronize::end() {
432 EventSafepointEnd event;
433 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id"
434
435 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
436 assert((_safepoint_counter & 0x1) == 1, "must be odd");
437 _safepoint_counter ++;
438 // memory fence isn't required here since an odd _safepoint_counter
439 // value can do no harm and a fence is issued below anyway.
440
441 DEBUG_ONLY(Thread* myThread = Thread::current();)
442 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
443
444 if (PrintSafepointStatistics) {
445 end_statistics(os::javaTimeNanos());
446 }
447
448 #ifdef ASSERT
449 // A pending_exception cannot be installed during a safepoint. The threads
450 // may install an async exception after they come back from a safepoint into
451 // pending_exception after they unblock. But that should happen later.
452 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
453 assert (!(cur->has_pending_exception() &&
454 cur->safepoint_state()->is_at_poll_safepoint()),
455 "safepoint installed a pending exception");
456 }
457 #endif // ASSERT
458
459 if (PageArmed) {
460 // Make polling safepoint aware
461 os::make_polling_page_readable();
462 PageArmed = 0 ;
463 }
464
465 // Remove safepoint check from interpreter
466 Interpreter::ignore_safepoints();
467
468 {
469 MutexLocker mu(Safepoint_lock);
470
471 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
472
473 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
474 // when they get restarted.
475 _state = _not_synchronized;
476 OrderAccess::fence();
477
478 log_debug(safepoint)("Leaving safepoint region");
479
480 // Start suspended threads
481 for(JavaThread *current = Threads::first(); current; current = current->next()) {
482 // A problem occurring on Solaris is when attempting to restart threads
483 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
484 // to the next one (since it has been running the longest). We then have
485 // to wait for a cpu to become available before we can continue restarting
486 // threads.
487 // FIXME: This causes the performance of the VM to degrade when active and with
488 // large numbers of threads. Apparently this is due to the synchronous nature
489 // of suspending threads.
490 //
491 // TODO-FIXME: the comments above are vestigial and no longer apply.
492 // Furthermore, using solaris' schedctl in this particular context confers no benefit
493 if (VMThreadHintNoPreempt) {
494 os::hint_no_preempt();
495 }
496 ThreadSafepointState* cur_state = current->safepoint_state();
497 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
498 cur_state->restart();
499 assert(cur_state->is_running(), "safepoint state has not been reset");
500 }
501
502 RuntimeService::record_safepoint_end();
503
504 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
505 // blocked in signal_thread_blocked
506 Threads_lock->unlock();
507
508 }
509 #if INCLUDE_ALL_GCS
510 // If there are any concurrent GC threads resume them.
511 if (UseConcMarkSweepGC) {
512 ConcurrentMarkSweepThread::desynchronize(false);
513 } else if (UseG1GC) {
514 SuspendibleThreadSet::desynchronize();
515 }
516 #endif // INCLUDE_ALL_GCS
517 // record this time so VMThread can keep track how much time has elapsed
518 // since last safepoint.
519 _end_of_last_safepoint = os::javaTimeMillis();
520
521 if (event.should_commit()) {
522 event.set_safepointId(safepoint_id);
523 event.commit();
524 }
525 }
526
527 bool SafepointSynchronize::is_cleanup_needed() {
528 // Need a safepoint if 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 ~ParallelSPCleanupThreadClosure() {
554 // This is here to be consistent with sweeper.cpp NMethodSweeper::mark_active_nmethods().
555 // TODO: Is this really needed?
556 OrderAccess::storestore();
557 }
558
559 void do_thread(Thread* thread) {
560 ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters);
561 if (_nmethod_cl != NULL && thread->is_Java_thread() &&
562 ! thread->is_Code_cache_sweeper_thread()) {
563 JavaThread* jt = (JavaThread*) thread;
564 jt->nmethods_do(_nmethod_cl);
565 }
566 }
567 };
568
569 class ParallelSPCleanupTask : public AbstractGangTask {
570 private:
571 SubTasksDone _subtasks;
572 ParallelSPCleanupThreadClosure _cleanup_threads_cl;
573 uint _num_workers;
574 DeflateMonitorCounters* _counters;
575 public:
576 ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
577 AbstractGangTask("Parallel Safepoint Cleanup"),
578 _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
579 _num_workers(num_workers),
580 _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)),
581 _counters(counters) {}
582
583 void work(uint worker_id) {
584 // All threads deflate monitors and mark nmethods (if necessary).
585 Threads::parallel_java_threads_do(&_cleanup_threads_cl);
586
587 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
588 const char* name = "deflating idle monitors";
589 EventSafepointCleanupTask event;
590 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
591 ObjectSynchronizer::deflate_idle_monitors(_counters);
592 event_safepoint_cleanup_task_commit(event, name);
593 }
594
595 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
596 const char* name = "updating inline caches";
597 EventSafepointCleanupTask event;
598 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
599 InlineCacheBuffer::update_inline_caches();
600 event_safepoint_cleanup_task_commit(event, name);
601 }
602
603 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
604 const char* name = "compilation policy safepoint handler";
605 EventSafepointCleanupTask event;
606 TraceTime timer("compilation policy safepoint handler", TRACETIME_LOG(Info, safepoint, cleanup));
607 CompilationPolicy::policy()->do_safepoint_work();
608 event_safepoint_cleanup_task_commit(event, name);
609 }
610
611 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
612 if (SymbolTable::needs_rehashing()) {
613 const char* name = "rehashing symbol table";
614 EventSafepointCleanupTask event;
615 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
616 SymbolTable::rehash_table();
617 event_safepoint_cleanup_task_commit(event, name);
618 }
619 }
620
621 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
622 if (StringTable::needs_rehashing()) {
623 const char* name = "rehashing string table";
624 EventSafepointCleanupTask event;
625 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
626 StringTable::rehash_table();
627 event_safepoint_cleanup_task_commit(event, name);
628 }
629 }
630
631 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) {
632 // CMS delays purging the CLDG until the beginning of the next safepoint and to
633 // make sure concurrent sweep is done
634 const char* name = "purging class loader data graph";
635 EventSafepointCleanupTask event;
636 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
637 ClassLoaderDataGraph::purge_if_needed();
638 event_safepoint_cleanup_task_commit(event, name);
639 }
640 _subtasks.all_tasks_completed(_num_workers);
641 }
642 };
643
644 // Various cleaning tasks that should be done periodically at safepoints.
645 void SafepointSynchronize::do_cleanup_tasks() {
646
647 // Prepare for monitor deflation.
648 DeflateMonitorCounters deflate_counters;
649 ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
650
651 CollectedHeap* heap = Universe::heap();
652 assert(heap != NULL, "heap not initialized yet?");
653 WorkGang* cleanup_workers = heap->get_safepoint_workers();
654 if (cleanup_workers != NULL) {
655 // Parallel cleanup using GC provided thread pool.
656 uint num_cleanup_workers = cleanup_workers->active_workers();
657 ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
658 StrongRootsScope srs(num_cleanup_workers);
659 cleanup_workers->run_task(&cleanup);
660 } else {
661 // Serial cleanup using VMThread.
662 ParallelSPCleanupTask cleanup(1, &deflate_counters);
663 StrongRootsScope srs(1);
664 cleanup.work(0);
665 }
666
667 // Finish monitor deflation.
668 ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
669 }
670
671
672 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
673 switch(state) {
674 case _thread_in_native:
675 // native threads are safe if they have no java stack or have walkable stack
676 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
677
678 // blocked threads should have already have walkable stack
679 case _thread_blocked:
680 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
681 return true;
682
683 default:
684 return false;
685 }
686 }
687
688
689 // See if the thread is running inside a lazy critical native and
690 // update the thread critical count if so. Also set a suspend flag to
691 // cause the native wrapper to return into the JVM to do the unlock
692 // once the native finishes.
693 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
694 if (state == _thread_in_native &&
695 thread->has_last_Java_frame() &&
696 thread->frame_anchor()->walkable()) {
697 // This thread might be in a critical native nmethod so look at
698 // the top of the stack and increment the critical count if it
699 // is.
700 frame wrapper_frame = thread->last_frame();
701 CodeBlob* stub_cb = wrapper_frame.cb();
702 if (stub_cb != NULL &&
703 stub_cb->is_nmethod() &&
704 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
705 // A thread could potentially be in a critical native across
706 // more than one safepoint, so only update the critical state on
707 // the first one. When it returns it will perform the unlock.
708 if (!thread->do_critical_native_unlock()) {
709 #ifdef ASSERT
710 if (!thread->in_critical()) {
711 GCLocker::increment_debug_jni_lock_count();
712 }
713 #endif
714 thread->enter_critical();
715 // Make sure the native wrapper calls back on return to
716 // perform the needed critical unlock.
717 thread->set_critical_native_unlock();
718 }
719 }
720 }
721 }
722
723
724
725 // -------------------------------------------------------------------------------------------------------
726 // Implementation of Safepoint callback point
727
728 void SafepointSynchronize::block(JavaThread *thread) {
729 assert(thread != NULL, "thread must be set");
730 assert(thread->is_Java_thread(), "not a Java thread");
731
732 // Threads shouldn't block if they are in the middle of printing, but...
733 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
734
735 // Only bail from the block() call if the thread is gone from the
736 // thread list; starting to exit should still block.
737 if (thread->is_terminated()) {
738 // block current thread if we come here from native code when VM is gone
739 thread->block_if_vm_exited();
740
741 // otherwise do nothing
742 return;
743 }
744
745 JavaThreadState state = thread->thread_state();
746 thread->frame_anchor()->make_walkable(thread);
747
748 // Check that we have a valid thread_state at this point
749 switch(state) {
750 case _thread_in_vm_trans:
751 case _thread_in_Java: // From compiled code
752
753 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
754 // we pretend we are still in the VM.
755 thread->set_thread_state(_thread_in_vm);
756
757 if (is_synchronizing()) {
758 Atomic::inc (&TryingToBlock) ;
759 }
760
761 // We will always be holding the Safepoint_lock when we are examine the state
762 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
763 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
764 Safepoint_lock->lock_without_safepoint_check();
765 if (is_synchronizing()) {
766 // Decrement the number of threads to wait for and signal vm thread
767 assert(_waiting_to_block > 0, "sanity check");
768 _waiting_to_block--;
769 thread->safepoint_state()->set_has_called_back(true);
770
771 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
772 if (thread->in_critical()) {
773 // Notice that this thread is in a critical section
774 increment_jni_active_count();
775 }
776
777 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
778 if (_waiting_to_block == 0) {
779 Safepoint_lock->notify_all();
780 }
781 }
782
783 // We transition the thread to state _thread_blocked here, but
784 // we can't do our usual check for external suspension and then
785 // self-suspend after the lock_without_safepoint_check() call
786 // below because we are often called during transitions while
787 // we hold different locks. That would leave us suspended while
788 // holding a resource which results in deadlocks.
789 thread->set_thread_state(_thread_blocked);
790 Safepoint_lock->unlock();
791
792 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
793 // the entire safepoint, the threads will all line up here during the safepoint.
794 Threads_lock->lock_without_safepoint_check();
795 // restore original state. This is important if the thread comes from compiled code, so it
796 // will continue to execute with the _thread_in_Java state.
797 thread->set_thread_state(state);
798 Threads_lock->unlock();
799 break;
800
801 case _thread_in_native_trans:
802 case _thread_blocked_trans:
803 case _thread_new_trans:
804 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
805 thread->print_thread_state();
806 fatal("Deadlock in safepoint code. "
807 "Should have called back to the VM before blocking.");
808 }
809
810 // We transition the thread to state _thread_blocked here, but
811 // we can't do our usual check for external suspension and then
812 // self-suspend after the lock_without_safepoint_check() call
813 // below because we are often called during transitions while
814 // we hold different locks. That would leave us suspended while
815 // holding a resource which results in deadlocks.
816 thread->set_thread_state(_thread_blocked);
817
818 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
819 // the safepoint code might still be waiting for it to block. We need to change the state here,
820 // so it can see that it is at a safepoint.
821
822 // Block until the safepoint operation is completed.
823 Threads_lock->lock_without_safepoint_check();
824
825 // Restore state
826 thread->set_thread_state(state);
827
828 Threads_lock->unlock();
829 break;
830
831 default:
832 fatal("Illegal threadstate encountered: %d", state);
833 }
834
835 // Check for pending. async. exceptions or suspends - except if the
836 // thread was blocked inside the VM. has_special_runtime_exit_condition()
837 // is called last since it grabs a lock and we only want to do that when
838 // we must.
839 //
840 // Note: we never deliver an async exception at a polling point as the
841 // compiler may not have an exception handler for it. The polling
842 // code will notice the async and deoptimize and the exception will
843 // be delivered. (Polling at a return point is ok though). Sure is
844 // a lot of bother for a deprecated feature...
845 //
846 // We don't deliver an async exception if the thread state is
847 // _thread_in_native_trans so JNI functions won't be called with
848 // a surprising pending exception. If the thread state is going back to java,
849 // async exception is checked in check_special_condition_for_native_trans().
850
851 if (state != _thread_blocked_trans &&
852 state != _thread_in_vm_trans &&
853 thread->has_special_runtime_exit_condition()) {
854 thread->handle_special_runtime_exit_condition(
855 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
856 }
857 }
858
859 // ------------------------------------------------------------------------------------------------------
860 // Exception handlers
861
862
863 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
864 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
865 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
866 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
867
868 if (ShowSafepointMsgs) {
869 tty->print("handle_polling_page_exception: ");
870 }
871
872 if (PrintSafepointStatistics) {
873 inc_page_trap_count();
874 }
875
876 ThreadSafepointState* state = thread->safepoint_state();
877
878 state->handle_polling_page_exception();
879 }
880
881
882 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
883 if (!timeout_error_printed) {
884 timeout_error_printed = true;
885 // Print out the thread info which didn't reach the safepoint for debugging
886 // purposes (useful when there are lots of threads in the debugger).
887 tty->cr();
888 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
889 if (reason == _spinning_timeout) {
890 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
891 } else if (reason == _blocking_timeout) {
892 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
893 }
894
895 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
896 ThreadSafepointState *cur_state;
897 ResourceMark rm;
898 for(JavaThread *cur_thread = Threads::first(); cur_thread;
899 cur_thread = cur_thread->next()) {
900 cur_state = cur_thread->safepoint_state();
901
902 if (cur_thread->thread_state() != _thread_blocked &&
903 ((reason == _spinning_timeout && cur_state->is_running()) ||
904 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
905 tty->print("# ");
906 cur_thread->print();
907 tty->cr();
908 }
909 }
910 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
911 }
912
913 // To debug the long safepoint, specify both DieOnSafepointTimeout &
914 // ShowMessageBoxOnError.
915 if (DieOnSafepointTimeout) {
916 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
917 SafepointTimeoutDelay, VMThread::vm_safepoint_description());
918 }
919 }
920
921
922 // -------------------------------------------------------------------------------------------------------
923 // Implementation of ThreadSafepointState
924
925 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
926 _thread = thread;
927 _type = _running;
928 _has_called_back = false;
929 _at_poll_safepoint = false;
930 }
931
932 void ThreadSafepointState::create(JavaThread *thread) {
933 ThreadSafepointState *state = new ThreadSafepointState(thread);
934 thread->set_safepoint_state(state);
935 }
936
937 void ThreadSafepointState::destroy(JavaThread *thread) {
938 if (thread->safepoint_state()) {
939 delete(thread->safepoint_state());
940 thread->set_safepoint_state(NULL);
941 }
942 }
943
944 void ThreadSafepointState::examine_state_of_thread() {
945 assert(is_running(), "better be running or just have hit safepoint poll");
946
947 JavaThreadState state = _thread->thread_state();
948
949 // Save the state at the start of safepoint processing.
950 _orig_thread_state = state;
951
952 // Check for a thread that is suspended. Note that thread resume tries
953 // to grab the Threads_lock which we own here, so a thread cannot be
954 // resumed during safepoint synchronization.
955
956 // We check to see if this thread is suspended without locking to
957 // avoid deadlocking with a third thread that is waiting for this
958 // thread to be suspended. The third thread can notice the safepoint
959 // that we're trying to start at the beginning of its SR_lock->wait()
960 // call. If that happens, then the third thread will block on the
961 // safepoint while still holding the underlying SR_lock. We won't be
962 // able to get the SR_lock and we'll deadlock.
963 //
964 // We don't need to grab the SR_lock here for two reasons:
965 // 1) The suspend flags are both volatile and are set with an
966 // Atomic::cmpxchg() call so we should see the suspended
967 // state right away.
968 // 2) We're being called from the safepoint polling loop; if
969 // we don't see the suspended state on this iteration, then
970 // we'll come around again.
971 //
972 bool is_suspended = _thread->is_ext_suspended();
973 if (is_suspended) {
974 roll_forward(_at_safepoint);
975 return;
976 }
977
978 // Some JavaThread states have an initial safepoint state of
979 // running, but are actually at a safepoint. We will happily
980 // agree and update the safepoint state here.
981 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
982 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
983 roll_forward(_at_safepoint);
984 return;
985 }
986
987 if (state == _thread_in_vm) {
988 roll_forward(_call_back);
989 return;
990 }
991
992 // All other thread states will continue to run until they
993 // transition and self-block in state _blocked
994 // Safepoint polling in compiled code causes the Java threads to do the same.
995 // Note: new threads may require a malloc so they must be allowed to finish
996
997 assert(is_running(), "examine_state_of_thread on non-running thread");
998 return;
999 }
1000
1001 // Returns true is thread could not be rolled forward at present position.
1002 void ThreadSafepointState::roll_forward(suspend_type type) {
1003 _type = type;
1004
1005 switch(_type) {
1006 case _at_safepoint:
1007 SafepointSynchronize::signal_thread_at_safepoint();
1008 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
1009 if (_thread->in_critical()) {
1010 // Notice that this thread is in a critical section
1011 SafepointSynchronize::increment_jni_active_count();
1012 }
1013 break;
1014
1015 case _call_back:
1016 set_has_called_back(false);
1017 break;
1018
1019 case _running:
1020 default:
1021 ShouldNotReachHere();
1022 }
1023 }
1024
1025 void ThreadSafepointState::restart() {
1026 switch(type()) {
1027 case _at_safepoint:
1028 case _call_back:
1029 break;
1030
1031 case _running:
1032 default:
1033 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
1034 p2i(_thread), _type);
1035 _thread->print();
1036 ShouldNotReachHere();
1037 }
1038 _type = _running;
1039 set_has_called_back(false);
1040 }
1041
1042
1043 void ThreadSafepointState::print_on(outputStream *st) const {
1044 const char *s = NULL;
1045
1046 switch(_type) {
1047 case _running : s = "_running"; break;
1048 case _at_safepoint : s = "_at_safepoint"; break;
1049 case _call_back : s = "_call_back"; break;
1050 default:
1051 ShouldNotReachHere();
1052 }
1053
1054 st->print_cr("Thread: " INTPTR_FORMAT
1055 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1056 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
1057 _at_poll_safepoint);
1058
1059 _thread->print_thread_state_on(st);
1060 }
1061
1062 // ---------------------------------------------------------------------------------------------------------------------
1063
1064 // Block the thread at the safepoint poll or poll return.
1065 void ThreadSafepointState::handle_polling_page_exception() {
1066
1067 // Check state. block() will set thread state to thread_in_vm which will
1068 // cause the safepoint state _type to become _call_back.
1069 assert(type() == ThreadSafepointState::_running,
1070 "polling page exception on thread not running state");
1071
1072 // Step 1: Find the nmethod from the return address
1073 if (ShowSafepointMsgs && Verbose) {
1074 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
1075 }
1076 address real_return_addr = thread()->saved_exception_pc();
1077
1078 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1079 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1080 CompiledMethod* nm = (CompiledMethod*)cb;
1081
1082 // Find frame of caller
1083 frame stub_fr = thread()->last_frame();
1084 CodeBlob* stub_cb = stub_fr.cb();
1085 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1086 RegisterMap map(thread(), true);
1087 frame caller_fr = stub_fr.sender(&map);
1088
1089 // Should only be poll_return or poll
1090 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1091
1092 // This is a poll immediately before a return. The exception handling code
1093 // has already had the effect of causing the return to occur, so the execution
1094 // will continue immediately after the call. In addition, the oopmap at the
1095 // return point does not mark the return value as an oop (if it is), so
1096 // it needs a handle here to be updated.
1097 if( nm->is_at_poll_return(real_return_addr) ) {
1098 // See if return type is an oop.
1099 bool return_oop = nm->method()->is_returning_oop();
1100 Handle return_value;
1101 if (return_oop) {
1102 // The oop result has been saved on the stack together with all
1103 // the other registers. In order to preserve it over GCs we need
1104 // to keep it in a handle.
1105 oop result = caller_fr.saved_oop_result(&map);
1106 assert(result == NULL || result->is_oop(), "must be oop");
1107 return_value = Handle(thread(), result);
1108 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1109 }
1110
1111 // Block the thread
1112 SafepointSynchronize::block(thread());
1113
1114 // restore oop result, if any
1115 if (return_oop) {
1116 caller_fr.set_saved_oop_result(&map, return_value());
1117 }
1118 }
1119
1120 // This is a safepoint poll. Verify the return address and block.
1121 else {
1122 set_at_poll_safepoint(true);
1123
1124 // verify the blob built the "return address" correctly
1125 assert(real_return_addr == caller_fr.pc(), "must match");
1126
1127 // Block the thread
1128 SafepointSynchronize::block(thread());
1129 set_at_poll_safepoint(false);
1130
1131 // If we have a pending async exception deoptimize the frame
1132 // as otherwise we may never deliver it.
1133 if (thread()->has_async_condition()) {
1134 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1135 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1136 }
1137
1138 // If an exception has been installed we must check for a pending deoptimization
1139 // Deoptimize frame if exception has been thrown.
1140
1141 if (thread()->has_pending_exception() ) {
1142 RegisterMap map(thread(), true);
1143 frame caller_fr = stub_fr.sender(&map);
1144 if (caller_fr.is_deoptimized_frame()) {
1145 // The exception patch will destroy registers that are still
1146 // live and will be needed during deoptimization. Defer the
1147 // Async exception should have deferred the exception until the
1148 // next safepoint which will be detected when we get into
1149 // the interpreter so if we have an exception now things
1150 // are messed up.
1151
1152 fatal("Exception installed and deoptimization is pending");
1153 }
1154 }
1155 }
1156 }
1157
1158
1159 //
1160 // Statistics & Instrumentations
1161 //
1162 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1163 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1164 int SafepointSynchronize::_cur_stat_index = 0;
1165 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1166 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1167 jlong SafepointSynchronize::_max_sync_time = 0;
1168 jlong SafepointSynchronize::_max_vmop_time = 0;
1169 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1170
1171 static jlong cleanup_end_time = 0;
1172 static bool need_to_track_page_armed_status = false;
1173 static bool init_done = false;
1174
1175 // Helper method to print the header.
1176 static void print_header() {
1177 // The number of spaces is significant here, and should match the format
1178 // specifiers in print_statistics().
1179
1180 tty->print(" vmop "
1181 "[ threads: total initially_running wait_to_block ]"
1182 "[ time: spin block sync cleanup vmop ] ");
1183
1184 // no page armed status printed out if it is always armed.
1185 if (need_to_track_page_armed_status) {
1186 tty->print("page_armed ");
1187 }
1188
1189 tty->print_cr("page_trap_count");
1190 }
1191
1192 void SafepointSynchronize::deferred_initialize_stat() {
1193 if (init_done) return;
1194
1195 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1196 // be printed right away, in which case, _safepoint_stats will regress to
1197 // a single element array. Otherwise, it is a circular ring buffer with default
1198 // size of PrintSafepointStatisticsCount.
1199 int stats_array_size;
1200 if (PrintSafepointStatisticsTimeout > 0) {
1201 stats_array_size = 1;
1202 PrintSafepointStatistics = true;
1203 } else {
1204 stats_array_size = PrintSafepointStatisticsCount;
1205 }
1206 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1207 * sizeof(SafepointStats), mtInternal);
1208 guarantee(_safepoint_stats != NULL,
1209 "not enough memory for safepoint instrumentation data");
1210
1211 if (DeferPollingPageLoopCount >= 0) {
1212 need_to_track_page_armed_status = true;
1213 }
1214 init_done = true;
1215 }
1216
1217 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1218 assert(init_done, "safepoint statistics array hasn't been initialized");
1219 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1220
1221 spstat->_time_stamp = _ts_of_current_safepoint;
1222
1223 VM_Operation *op = VMThread::vm_operation();
1224 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1225 if (op != NULL) {
1226 _safepoint_reasons[spstat->_vmop_type]++;
1227 }
1228
1229 spstat->_nof_total_threads = nof_threads;
1230 spstat->_nof_initial_running_threads = nof_running;
1231 spstat->_nof_threads_hit_page_trap = 0;
1232
1233 // Records the start time of spinning. The real time spent on spinning
1234 // will be adjusted when spin is done. Same trick is applied for time
1235 // spent on waiting for threads to block.
1236 if (nof_running != 0) {
1237 spstat->_time_to_spin = os::javaTimeNanos();
1238 } else {
1239 spstat->_time_to_spin = 0;
1240 }
1241 }
1242
1243 void SafepointSynchronize::update_statistics_on_spin_end() {
1244 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1245
1246 jlong cur_time = os::javaTimeNanos();
1247
1248 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1249 if (spstat->_nof_initial_running_threads != 0) {
1250 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1251 }
1252
1253 if (need_to_track_page_armed_status) {
1254 spstat->_page_armed = (PageArmed == 1);
1255 }
1256
1257 // Records the start time of waiting for to block. Updated when block is done.
1258 if (_waiting_to_block != 0) {
1259 spstat->_time_to_wait_to_block = cur_time;
1260 } else {
1261 spstat->_time_to_wait_to_block = 0;
1262 }
1263 }
1264
1265 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1266 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1267
1268 if (spstat->_nof_threads_wait_to_block != 0) {
1269 spstat->_time_to_wait_to_block = end_time -
1270 spstat->_time_to_wait_to_block;
1271 }
1272
1273 // Records the end time of sync which will be used to calculate the total
1274 // vm operation time. Again, the real time spending in syncing will be deducted
1275 // from the start of the sync time later when end_statistics is called.
1276 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1277 if (spstat->_time_to_sync > _max_sync_time) {
1278 _max_sync_time = spstat->_time_to_sync;
1279 }
1280
1281 spstat->_time_to_do_cleanups = end_time;
1282 }
1283
1284 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1285 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1286
1287 // Record how long spent in cleanup tasks.
1288 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1289
1290 cleanup_end_time = end_time;
1291 }
1292
1293 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1294 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1295
1296 // Update the vm operation time.
1297 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1298 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1299 _max_vmop_time = spstat->_time_to_exec_vmop;
1300 }
1301 // Only the sync time longer than the specified
1302 // PrintSafepointStatisticsTimeout will be printed out right away.
1303 // By default, it is -1 meaning all samples will be put into the list.
1304 if ( PrintSafepointStatisticsTimeout > 0) {
1305 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1306 print_statistics();
1307 }
1308 } else {
1309 // The safepoint statistics will be printed out when the _safepoin_stats
1310 // array fills up.
1311 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1312 print_statistics();
1313 _cur_stat_index = 0;
1314 } else {
1315 _cur_stat_index++;
1316 }
1317 }
1318 }
1319
1320 void SafepointSynchronize::print_statistics() {
1321 for (int index = 0; index <= _cur_stat_index; index++) {
1322 if (index % 30 == 0) {
1323 print_header();
1324 }
1325 SafepointStats* sstats = &_safepoint_stats[index];
1326 tty->print("%8.3f: ", sstats->_time_stamp);
1327 tty->print("%-30s [ "
1328 INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " "
1329 "]",
1330 (sstats->_vmop_type == -1 ? "no vm operation" : VM_Operation::name(sstats->_vmop_type)),
1331 sstats->_nof_total_threads,
1332 sstats->_nof_initial_running_threads,
1333 sstats->_nof_threads_wait_to_block);
1334 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1335 tty->print("[ "
1336 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1337 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1338 INT64_FORMAT_W(7) " ] ",
1339 sstats->_time_to_spin / MICROUNITS,
1340 sstats->_time_to_wait_to_block / MICROUNITS,
1341 sstats->_time_to_sync / MICROUNITS,
1342 sstats->_time_to_do_cleanups / MICROUNITS,
1343 sstats->_time_to_exec_vmop / MICROUNITS);
1344
1345 if (need_to_track_page_armed_status) {
1346 tty->print(INT32_FORMAT_W(10) " ", sstats->_page_armed);
1347 }
1348 tty->print_cr(INT32_FORMAT_W(15) " ", sstats->_nof_threads_hit_page_trap);
1349 }
1350 }
1351
1352 // This method will be called when VM exits. It will first call
1353 // print_statistics to print out the rest of the sampling. Then
1354 // it tries to summarize the sampling.
1355 void SafepointSynchronize::print_stat_on_exit() {
1356 if (_safepoint_stats == NULL) return;
1357
1358 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1359
1360 // During VM exit, end_statistics may not get called and in that
1361 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1362 // don't print it out.
1363 // Approximate the vm op time.
1364 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1365 os::javaTimeNanos() - cleanup_end_time;
1366
1367 if ( PrintSafepointStatisticsTimeout < 0 ||
1368 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1369 print_statistics();
1370 }
1371 tty->cr();
1372
1373 // Print out polling page sampling status.
1374 if (!need_to_track_page_armed_status) {
1375 tty->print_cr("Polling page always armed");
1376 } else {
1377 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
1378 DeferPollingPageLoopCount);
1379 }
1380
1381 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1382 if (_safepoint_reasons[index] != 0) {
1383 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1384 _safepoint_reasons[index]);
1385 }
1386 }
1387
1388 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1389 _coalesced_vmop_count);
1390 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1391 _max_sync_time / MICROUNITS);
1392 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1393 INT64_FORMAT_W(5) " ms",
1394 _max_vmop_time / MICROUNITS);
1395 }
1396
1397 // ------------------------------------------------------------------------------------------------
1398 // Non-product code
1399
1400 #ifndef PRODUCT
1401
1402 void SafepointSynchronize::print_state() {
1403 if (_state == _not_synchronized) {
1404 tty->print_cr("not synchronized");
1405 } else if (_state == _synchronizing || _state == _synchronized) {
1406 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1407 "synchronized");
1408
1409 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1410 cur->safepoint_state()->print();
1411 }
1412 }
1413 }
1414
1415 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1416 if (ShowSafepointMsgs) {
1417 va_list ap;
1418 va_start(ap, format);
1419 tty->vprint_cr(format, ap);
1420 va_end(ap);
1421 }
1422 }
1423
1424 #endif // !PRODUCT