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 WorkGang* SafepointSynchronize::_cleanup_workers = NULL;
75 SubTasksDone* SafepointSynchronize::_cleanup_subtasks = NULL;
76 uint SafepointSynchronize::_num_cleanup_workers = 0;
77
78 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
79 volatile int SafepointSynchronize::_waiting_to_block = 0;
80 volatile int SafepointSynchronize::_safepoint_counter = 0;
81 int SafepointSynchronize::_current_jni_active_count = 0;
82 long SafepointSynchronize::_end_of_last_safepoint = 0;
83 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
84 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
85 static bool timeout_error_printed = false;
86
87 // Roll all threads forward to a safepoint and suspend them all
88 void SafepointSynchronize::begin() {
89 EventSafepointBegin begin_event;
90 Thread* myThread = Thread::current();
91 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
92
93 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
94 _safepoint_begin_time = os::javaTimeNanos();
95 _ts_of_current_safepoint = tty->time_stamp().seconds();
96 }
97
98 #if INCLUDE_ALL_GCS
99 if (UseConcMarkSweepGC) {
100 // In the future we should investigate whether CMS can use the
101 // more-general mechanism below. DLD (01/05).
102 ConcurrentMarkSweepThread::synchronize(false);
103 } else if (UseG1GC) {
104 SuspendibleThreadSet::synchronize();
105 }
106 #endif // INCLUDE_ALL_GCS
107
108 // By getting the Threads_lock, we assure that no threads are about to start or
109 // exit. It is released again in SafepointSynchronize::end().
110 Threads_lock->lock();
111
112 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
113
114 int nof_threads = Threads::number_of_threads();
115
116 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads);
117
118 RuntimeService::record_safepoint_begin();
119
120 MutexLocker mu(Safepoint_lock);
121
122 // Reset the count of active JNI critical threads
123 _current_jni_active_count = 0;
124
125 // Set number of threads to wait for, before we initiate the callbacks
126 _waiting_to_block = nof_threads;
127 TryingToBlock = 0 ;
128 int still_running = nof_threads;
129
130 // Save the starting time, so that it can be compared to see if this has taken
131 // too long to complete.
132 jlong safepoint_limit_time = 0;
133 timeout_error_printed = false;
134
135 // PrintSafepointStatisticsTimeout can be specified separately. When
136 // specified, PrintSafepointStatistics will be set to true in
137 // deferred_initialize_stat method. The initialization has to be done
138 // early enough to avoid any races. See bug 6880029 for details.
139 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
140 deferred_initialize_stat();
141 }
142
143 // Begin the process of bringing the system to a safepoint.
144 // Java threads can be in several different states and are
145 // stopped by different mechanisms:
146 //
147 // 1. Running interpreted
148 // The interpreter dispatch table is changed to force it to
149 // check for a safepoint condition between bytecodes.
150 // 2. Running in native code
151 // When returning from the native code, a Java thread must check
152 // the safepoint _state to see if we must block. If the
153 // VM thread sees a Java thread in native, it does
154 // not wait for this thread to block. The order of the memory
155 // writes and reads of both the safepoint state and the Java
156 // threads state is critical. In order to guarantee that the
157 // memory writes are serialized with respect to each other,
158 // the VM thread issues a memory barrier instruction
159 // (on MP systems). In order to avoid the overhead of issuing
160 // a memory barrier for each Java thread making native calls, each Java
161 // thread performs a write to a single memory page after changing
162 // the thread state. The VM thread performs a sequence of
163 // mprotect OS calls which forces all previous writes from all
164 // Java threads to be serialized. This is done in the
165 // os::serialize_thread_states() call. This has proven to be
166 // much more efficient than executing a membar instruction
167 // on every call to native code.
168 // 3. Running compiled Code
169 // Compiled code reads a global (Safepoint Polling) page that
170 // is set to fault if we are trying to get to a safepoint.
171 // 4. Blocked
172 // A thread which is blocked will not be allowed to return from the
173 // block condition until the safepoint operation is complete.
174 // 5. In VM or Transitioning between states
175 // If a Java thread is currently running in the VM or transitioning
176 // between states, the safepointing code will wait for the thread to
177 // block itself when it attempts transitions to a new state.
178 //
179 {
180 EventSafepointStateSynchronization sync_event;
181 int initial_running = 0;
182
183 _state = _synchronizing;
184 OrderAccess::fence();
185
186 // Flush all thread states to memory
187 if (!UseMembar) {
188 os::serialize_thread_states();
189 }
190
191 // Make interpreter safepoint aware
192 Interpreter::notice_safepoints();
193
194 if (DeferPollingPageLoopCount < 0) {
195 // Make polling safepoint aware
196 guarantee (PageArmed == 0, "invariant") ;
197 PageArmed = 1 ;
198 os::make_polling_page_unreadable();
199 }
200
201 // Consider using active_processor_count() ... but that call is expensive.
202 int ncpus = os::processor_count() ;
203
204 #ifdef ASSERT
205 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
206 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
207 // Clear the visited flag to ensure that the critical counts are collected properly.
208 cur->set_visited_for_critical_count(false);
209 }
210 #endif // ASSERT
211
212 if (SafepointTimeout)
213 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
214
215 // Iterate through all threads until it have been determined how to stop them all at a safepoint
216 unsigned int iterations = 0;
217 int steps = 0 ;
218 while(still_running > 0) {
219 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
220 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
221 ThreadSafepointState *cur_state = cur->safepoint_state();
222 if (cur_state->is_running()) {
223 cur_state->examine_state_of_thread();
224 if (!cur_state->is_running()) {
225 still_running--;
226 // consider adjusting steps downward:
227 // steps = 0
228 // steps -= NNN
229 // steps >>= 1
230 // steps = MIN(steps, 2000-100)
231 // if (iterations != 0) steps -= NNN
232 }
233 if (log_is_enabled(Trace, safepoint)) {
234 ResourceMark rm;
235 cur_state->print_on(Log(safepoint)::trace_stream());
236 }
237 }
238 }
239
240 if (iterations == 0) {
241 initial_running = still_running;
242 if (PrintSafepointStatistics) {
243 begin_statistics(nof_threads, still_running);
244 }
245 }
246
247 if (still_running > 0) {
248 // Check for if it takes to long
249 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
250 print_safepoint_timeout(_spinning_timeout);
251 }
252
253 // Spin to avoid context switching.
254 // There's a tension between allowing the mutators to run (and rendezvous)
255 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
256 // a mutator might otherwise use profitably to reach a safepoint. Excessive
257 // spinning by the VM thread on a saturated system can increase rendezvous latency.
258 // Blocking or yielding incur their own penalties in the form of context switching
259 // and the resultant loss of $ residency.
260 //
261 // Further complicating matters is that yield() does not work as naively expected
262 // on many platforms -- yield() does not guarantee that any other ready threads
263 // will run. As such we revert to naked_short_sleep() after some number of iterations.
264 // nakes_short_sleep() is implemented as a short unconditional sleep.
265 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
266 // can actually increase the time it takes the VM thread to detect that a system-wide
267 // stop-the-world safepoint has been reached. In a pathological scenario such as that
268 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
269 // In that case the mutators will be stalled waiting for the safepoint to complete and the
270 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
271 // will eventually wake up and detect that all mutators are safe, at which point
272 // we'll again make progress.
273 //
274 // Beware too that that the VMThread typically runs at elevated priority.
275 // Its default priority is higher than the default mutator priority.
276 // Obviously, this complicates spinning.
277 //
278 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
279 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
280 //
281 // See the comments in synchronizer.cpp for additional remarks on spinning.
282 //
283 // In the future we might:
284 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
285 // This is tricky as the path used by a thread exiting the JVM (say on
286 // on JNI call-out) simply stores into its state field. The burden
287 // is placed on the VM thread, which must poll (spin).
288 // 2. Find something useful to do while spinning. If the safepoint is GC-related
289 // we might aggressively scan the stacks of threads that are already safe.
290 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
291 // If all the mutators are ONPROC there's no reason to sleep or yield.
292 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
293 // 5. Check system saturation. If the system is not fully saturated then
294 // simply spin and avoid sleep/yield.
295 // 6. As still-running mutators rendezvous they could unpark the sleeping
296 // VMthread. This works well for still-running mutators that become
297 // safe. The VMthread must still poll for mutators that call-out.
298 // 7. Drive the policy on time-since-begin instead of iterations.
299 // 8. Consider making the spin duration a function of the # of CPUs:
300 // Spin = (((ncpus-1) * M) + K) + F(still_running)
301 // Alternately, instead of counting iterations of the outer loop
302 // we could count the # of threads visited in the inner loop, above.
303 // 9. On windows consider using the return value from SwitchThreadTo()
304 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
305
306 if (int(iterations) == DeferPollingPageLoopCount) {
307 guarantee (PageArmed == 0, "invariant") ;
308 PageArmed = 1 ;
309 os::make_polling_page_unreadable();
310 }
311
312 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
313 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
314 ++steps ;
315 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
316 SpinPause() ; // MP-Polite spin
317 } else
318 if (steps < DeferThrSuspendLoopCount) {
319 os::naked_yield() ;
320 } else {
321 os::naked_short_sleep(1);
322 }
323
324 iterations ++ ;
325 }
326 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
327 }
328 assert(still_running == 0, "sanity check");
329
330 if (PrintSafepointStatistics) {
331 update_statistics_on_spin_end();
332 }
333
334 if (sync_event.should_commit()) {
335 sync_event.set_safepointId(safepoint_counter());
336 sync_event.set_initialThreadCount(initial_running);
337 sync_event.set_runningThreadCount(_waiting_to_block);
338 sync_event.set_iterations(iterations);
339 sync_event.commit();
340 }
341 } //EventSafepointStateSync
342
343 // wait until all threads are stopped
344 {
345 EventSafepointWaitBlocked wait_blocked_event;
346 int initial_waiting_to_block = _waiting_to_block;
347
348 while (_waiting_to_block > 0) {
349 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
350 if (!SafepointTimeout || timeout_error_printed) {
351 Safepoint_lock->wait(true); // true, means with no safepoint checks
352 } else {
353 // Compute remaining time
354 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
355
356 // If there is no remaining time, then there is an error
357 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
358 print_safepoint_timeout(_blocking_timeout);
359 }
360 }
361 }
362 assert(_waiting_to_block == 0, "sanity check");
363
364 #ifndef PRODUCT
365 if (SafepointTimeout) {
366 jlong current_time = os::javaTimeNanos();
367 if (safepoint_limit_time < current_time) {
368 tty->print_cr("# SafepointSynchronize: Finished after "
369 INT64_FORMAT_W(6) " ms",
370 ((current_time - safepoint_limit_time) / MICROUNITS +
371 (jlong)SafepointTimeoutDelay));
372 }
373 }
374 #endif
375
376 assert((_safepoint_counter & 0x1) == 0, "must be even");
377 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
378 _safepoint_counter ++;
379
380 // Record state
381 _state = _synchronized;
382
383 OrderAccess::fence();
384
385 if (wait_blocked_event.should_commit()) {
386 wait_blocked_event.set_safepointId(safepoint_counter());
387 wait_blocked_event.set_runningThreadCount(initial_waiting_to_block);
388 wait_blocked_event.commit();
389 }
390 } // EventSafepointWaitBlocked
391
392 #ifdef ASSERT
393 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
394 // make sure all the threads were visited
395 assert(cur->was_visited_for_critical_count(), "missed a thread");
396 }
397 #endif // ASSERT
398
399 // Update the count of active JNI critical regions
400 GCLocker::set_jni_lock_count(_current_jni_active_count);
401
402 if (log_is_enabled(Debug, safepoint)) {
403 log_debug(safepoint)("Entering safepoint region: %s", VMThread::vm_safepoint_description());
404 }
405
406 RuntimeService::record_safepoint_synchronized();
407 if (PrintSafepointStatistics) {
408 update_statistics_on_sync_end(os::javaTimeNanos());
409 }
410
411 // Call stuff that needs to be run when a safepoint is just about to be completed
412 {
413 EventSafepointCleanup cleanup_event;
414 do_cleanup_tasks();
415 if (cleanup_event.should_commit()) {
416 cleanup_event.set_safepointId(safepoint_counter());
417 cleanup_event.commit();
418 }
419 }
420
421 if (PrintSafepointStatistics) {
422 // Record how much time spend on the above cleanup tasks
423 update_statistics_on_cleanup_end(os::javaTimeNanos());
424 }
425 if (begin_event.should_commit()) {
426 begin_event.set_safepointId(safepoint_counter());
427 begin_event.set_totalThreadCount(nof_threads);
428 begin_event.set_jniCriticalThreadCount(_current_jni_active_count);
429 begin_event.commit();
430 }
431 }
432
433 // Wake up all threads, so they are ready to resume execution after the safepoint
434 // operation has been carried out
435 void SafepointSynchronize::end() {
436 EventSafepointEnd event;
437 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id"
438
439 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
440 assert((_safepoint_counter & 0x1) == 1, "must be odd");
441 _safepoint_counter ++;
442 // memory fence isn't required here since an odd _safepoint_counter
443 // value can do no harm and a fence is issued below anyway.
444
445 DEBUG_ONLY(Thread* myThread = Thread::current();)
446 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
447
448 if (PrintSafepointStatistics) {
449 end_statistics(os::javaTimeNanos());
450 }
451
452 #ifdef ASSERT
453 // A pending_exception cannot be installed during a safepoint. The threads
454 // may install an async exception after they come back from a safepoint into
455 // pending_exception after they unblock. But that should happen later.
456 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
457 assert (!(cur->has_pending_exception() &&
458 cur->safepoint_state()->is_at_poll_safepoint()),
459 "safepoint installed a pending exception");
460 }
461 #endif // ASSERT
462
463 if (PageArmed) {
464 // Make polling safepoint aware
465 os::make_polling_page_readable();
466 PageArmed = 0 ;
467 }
468
469 // Remove safepoint check from interpreter
470 Interpreter::ignore_safepoints();
471
472 {
473 MutexLocker mu(Safepoint_lock);
474
475 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
476
477 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
478 // when they get restarted.
479 _state = _not_synchronized;
480 OrderAccess::fence();
481
482 log_debug(safepoint)("Leaving safepoint region");
483
484 // Start suspended threads
485 for(JavaThread *current = Threads::first(); current; current = current->next()) {
486 // A problem occurring on Solaris is when attempting to restart threads
487 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
488 // to the next one (since it has been running the longest). We then have
489 // to wait for a cpu to become available before we can continue restarting
490 // threads.
491 // FIXME: This causes the performance of the VM to degrade when active and with
492 // large numbers of threads. Apparently this is due to the synchronous nature
493 // of suspending threads.
494 //
495 // TODO-FIXME: the comments above are vestigial and no longer apply.
496 // Furthermore, using solaris' schedctl in this particular context confers no benefit
497 if (VMThreadHintNoPreempt) {
498 os::hint_no_preempt();
499 }
500 ThreadSafepointState* cur_state = current->safepoint_state();
501 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
502 cur_state->restart();
503 assert(cur_state->is_running(), "safepoint state has not been reset");
504 }
505
506 RuntimeService::record_safepoint_end();
507
508 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
509 // blocked in signal_thread_blocked
510 Threads_lock->unlock();
511
512 }
513 #if INCLUDE_ALL_GCS
514 // If there are any concurrent GC threads resume them.
515 if (UseConcMarkSweepGC) {
516 ConcurrentMarkSweepThread::desynchronize(false);
517 } else if (UseG1GC) {
518 SuspendibleThreadSet::desynchronize();
519 }
520 #endif // INCLUDE_ALL_GCS
521 // record this time so VMThread can keep track how much time has elapsed
522 // since last safepoint.
523 _end_of_last_safepoint = os::javaTimeMillis();
524
525 if (event.should_commit()) {
526 event.set_safepointId(safepoint_id);
527 event.commit();
528 }
529 }
530
531 bool SafepointSynchronize::is_cleanup_needed() {
532 // Need a safepoint if some inline cache buffers is non-empty
533 if (!InlineCacheBuffer::is_empty()) return true;
534 return false;
535 }
536
537 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) {
538 if (event.should_commit()) {
539 event.set_safepointId(SafepointSynchronize::safepoint_counter());
540 event.set_name(name);
541 event.commit();
542 }
543 }
544
545 class ParallelSPCleanupThreadClosure : public ThreadClosure {
546 private:
547 CodeBlobClosure* _nmethod_cl;
548
549 public:
550 ParallelSPCleanupThreadClosure() {
551 _nmethod_cl = NMethodSweeper::prepare_mark_active_nmethods();
552 }
553
554 void do_thread(Thread* thread) {
555 ObjectSynchronizer::deflate_thread_local_monitors(thread);
556 if (_nmethod_cl != NULL && thread->is_Java_thread() &&
557 ! thread->is_Code_cache_sweeper_thread()) {
558 JavaThread* jt = (JavaThread*) thread;
559 jt->nmethods_do(_nmethod_cl);
560 }
561 }
562 };
563
564 class ParallelSPCleanupTask : public AbstractGangTask {
565 private:
566 SubTasksDone* _subtasks;
567 ParallelSPCleanupThreadClosure _cleanup_threads_cl;
568 public:
569 ParallelSPCleanupTask(SubTasksDone* subtasks) :
570 AbstractGangTask("Parallel Safepoint Cleanup"),
571 _cleanup_threads_cl(ParallelSPCleanupThreadClosure()),
572 _subtasks(subtasks) {}
573
574 void work(uint worker_id) {
575 // All threads deflate monitors and mark nmethods (if necessary).
576 Threads::parallel_java_threads_do(&_cleanup_threads_cl);
577
578 if (! _subtasks->is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
579 const char* name = "deflating idle monitors";
580 EventSafepointCleanupTask event;
581 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
582 ObjectSynchronizer::deflate_idle_monitors();
583 event_safepoint_cleanup_task_commit(event, name);
584 }
585
586 if (! _subtasks->is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
587 const char* name = "updating inline caches";
588 EventSafepointCleanupTask event;
589 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
590 InlineCacheBuffer::update_inline_caches();
591 event_safepoint_cleanup_task_commit(event, name);
592 }
593
594 if (! _subtasks->is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
595 const char* name = "compilation policy safepoint handler";
596 EventSafepointCleanupTask event;
597 TraceTime timer("compilation policy safepoint handler", TRACETIME_LOG(Info, safepoint, cleanup));
598 CompilationPolicy::policy()->do_safepoint_work();
599 event_safepoint_cleanup_task_commit(event, name);
600 }
601
602 if (! _subtasks->is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
603 if (SymbolTable::needs_rehashing()) {
604 const char* name = "rehashing symbol table";
605 EventSafepointCleanupTask event;
606 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
607 SymbolTable::rehash_table();
608 event_safepoint_cleanup_task_commit(event, name);
609 }
610 }
611
612 if (! _subtasks->is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
613 if (StringTable::needs_rehashing()) {
614 const char* name = "rehashing string table";
615 EventSafepointCleanupTask event;
616 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
617 StringTable::rehash_table();
618 event_safepoint_cleanup_task_commit(event, name);
619 }
620 }
621
622 if (! _subtasks->is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) {
623 // CMS delays purging the CLDG until the beginning of the next safepoint and to
624 // make sure concurrent sweep is done
625 const char* name = "purging class loader data graph";
626 EventSafepointCleanupTask event;
627 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
628 ClassLoaderDataGraph::purge_if_needed();
629 event_safepoint_cleanup_task_commit(event, name);
630 }
631 _subtasks->all_tasks_completed(SafepointSynchronize::_num_cleanup_workers);
632 }
633 };
634
635 // Various cleaning tasks that should be done periodically at safepoints
636 void SafepointSynchronize::do_cleanup_tasks() {
637 if (_num_cleanup_workers == 0) {
638 // Deferred initialization.
639 if (ParallelSafepointCleanup) {
640 assert(_cleanup_workers == NULL, "already initialized?");
641 // Ask the GC to share its workers.
642 CollectedHeap* heap = Universe::heap();
643 assert(heap != NULL, "heap not initialized yet?");
644 _cleanup_workers = heap->get_safepoint_workers();
645 if (_cleanup_workers == NULL) {
646 // If GC doesn't want to share or doesn't even use worker threads, we create our own thread pool.
647 _cleanup_workers = new WorkGang("Parallel Safepoint Cleanup", ParallelSafepointCleanupThreads, false, false);
648 _cleanup_workers->initialize_workers();
649 }
650 _num_cleanup_workers = MIN2(ParallelSafepointCleanupThreads, _cleanup_workers->total_workers());
651 } else {
652 _num_cleanup_workers = 1;
653 }
654 assert(_num_cleanup_workers != 0, "not initialized?");
655 _cleanup_subtasks = new SubTasksDone(SAFEPOINT_CLEANUP_NUM_TASKS);
656 }
657
658 // Run cleanup serially or in parallel.
659 ParallelSPCleanupTask cleanup(_cleanup_subtasks);
660 StrongRootsScope srs(_num_cleanup_workers);
661 if (ParallelSafepointCleanup) {
662 assert(_cleanup_workers != NULL, "no cleanup workers?");
663 _cleanup_workers->run_task(&cleanup, _num_cleanup_workers);
664 } else {
665 assert(_num_cleanup_workers == 1, "only 1 thread");
666 cleanup.work(0);
667 }
668 }
669
670 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
671 switch(state) {
672 case _thread_in_native:
673 // native threads are safe if they have no java stack or have walkable stack
674 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
675
676 // blocked threads should have already have walkable stack
677 case _thread_blocked:
678 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
679 return true;
680
681 default:
682 return false;
683 }
684 }
685
686
687 // See if the thread is running inside a lazy critical native and
688 // update the thread critical count if so. Also set a suspend flag to
689 // cause the native wrapper to return into the JVM to do the unlock
690 // once the native finishes.
691 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
692 if (state == _thread_in_native &&
693 thread->has_last_Java_frame() &&
694 thread->frame_anchor()->walkable()) {
695 // This thread might be in a critical native nmethod so look at
696 // the top of the stack and increment the critical count if it
697 // is.
698 frame wrapper_frame = thread->last_frame();
699 CodeBlob* stub_cb = wrapper_frame.cb();
700 if (stub_cb != NULL &&
701 stub_cb->is_nmethod() &&
702 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
703 // A thread could potentially be in a critical native across
704 // more than one safepoint, so only update the critical state on
705 // the first one. When it returns it will perform the unlock.
706 if (!thread->do_critical_native_unlock()) {
707 #ifdef ASSERT
708 if (!thread->in_critical()) {
709 GCLocker::increment_debug_jni_lock_count();
710 }
711 #endif
712 thread->enter_critical();
713 // Make sure the native wrapper calls back on return to
714 // perform the needed critical unlock.
715 thread->set_critical_native_unlock();
716 }
717 }
718 }
719 }
720
721
722
723 // -------------------------------------------------------------------------------------------------------
724 // Implementation of Safepoint callback point
725
726 void SafepointSynchronize::block(JavaThread *thread) {
727 assert(thread != NULL, "thread must be set");
728 assert(thread->is_Java_thread(), "not a Java thread");
729
730 // Threads shouldn't block if they are in the middle of printing, but...
731 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
732
733 // Only bail from the block() call if the thread is gone from the
734 // thread list; starting to exit should still block.
735 if (thread->is_terminated()) {
736 // block current thread if we come here from native code when VM is gone
737 thread->block_if_vm_exited();
738
739 // otherwise do nothing
740 return;
741 }
742
743 JavaThreadState state = thread->thread_state();
744 thread->frame_anchor()->make_walkable(thread);
745
746 // Check that we have a valid thread_state at this point
747 switch(state) {
748 case _thread_in_vm_trans:
749 case _thread_in_Java: // From compiled code
750
751 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
752 // we pretend we are still in the VM.
753 thread->set_thread_state(_thread_in_vm);
754
755 if (is_synchronizing()) {
756 Atomic::inc (&TryingToBlock) ;
757 }
758
759 // We will always be holding the Safepoint_lock when we are examine the state
760 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
761 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
762 Safepoint_lock->lock_without_safepoint_check();
763 if (is_synchronizing()) {
764 // Decrement the number of threads to wait for and signal vm thread
765 assert(_waiting_to_block > 0, "sanity check");
766 _waiting_to_block--;
767 thread->safepoint_state()->set_has_called_back(true);
768
769 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
770 if (thread->in_critical()) {
771 // Notice that this thread is in a critical section
772 increment_jni_active_count();
773 }
774
775 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
776 if (_waiting_to_block == 0) {
777 Safepoint_lock->notify_all();
778 }
779 }
780
781 // We transition the thread to state _thread_blocked here, but
782 // we can't do our usual check for external suspension and then
783 // self-suspend after the lock_without_safepoint_check() call
784 // below because we are often called during transitions while
785 // we hold different locks. That would leave us suspended while
786 // holding a resource which results in deadlocks.
787 thread->set_thread_state(_thread_blocked);
788 Safepoint_lock->unlock();
789
790 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
791 // the entire safepoint, the threads will all line up here during the safepoint.
792 Threads_lock->lock_without_safepoint_check();
793 // restore original state. This is important if the thread comes from compiled code, so it
794 // will continue to execute with the _thread_in_Java state.
795 thread->set_thread_state(state);
796 Threads_lock->unlock();
797 break;
798
799 case _thread_in_native_trans:
800 case _thread_blocked_trans:
801 case _thread_new_trans:
802 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
803 thread->print_thread_state();
804 fatal("Deadlock in safepoint code. "
805 "Should have called back to the VM before blocking.");
806 }
807
808 // We transition the thread to state _thread_blocked here, but
809 // we can't do our usual check for external suspension and then
810 // self-suspend after the lock_without_safepoint_check() call
811 // below because we are often called during transitions while
812 // we hold different locks. That would leave us suspended while
813 // holding a resource which results in deadlocks.
814 thread->set_thread_state(_thread_blocked);
815
816 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
817 // the safepoint code might still be waiting for it to block. We need to change the state here,
818 // so it can see that it is at a safepoint.
819
820 // Block until the safepoint operation is completed.
821 Threads_lock->lock_without_safepoint_check();
822
823 // Restore state
824 thread->set_thread_state(state);
825
826 Threads_lock->unlock();
827 break;
828
829 default:
830 fatal("Illegal threadstate encountered: %d", state);
831 }
832
833 // Check for pending. async. exceptions or suspends - except if the
834 // thread was blocked inside the VM. has_special_runtime_exit_condition()
835 // is called last since it grabs a lock and we only want to do that when
836 // we must.
837 //
838 // Note: we never deliver an async exception at a polling point as the
839 // compiler may not have an exception handler for it. The polling
840 // code will notice the async and deoptimize and the exception will
841 // be delivered. (Polling at a return point is ok though). Sure is
842 // a lot of bother for a deprecated feature...
843 //
844 // We don't deliver an async exception if the thread state is
845 // _thread_in_native_trans so JNI functions won't be called with
846 // a surprising pending exception. If the thread state is going back to java,
847 // async exception is checked in check_special_condition_for_native_trans().
848
849 if (state != _thread_blocked_trans &&
850 state != _thread_in_vm_trans &&
851 thread->has_special_runtime_exit_condition()) {
852 thread->handle_special_runtime_exit_condition(
853 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
854 }
855 }
856
857 // ------------------------------------------------------------------------------------------------------
858 // Exception handlers
859
860
861 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
862 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
863 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
864 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
865
866 if (ShowSafepointMsgs) {
867 tty->print("handle_polling_page_exception: ");
868 }
869
870 if (PrintSafepointStatistics) {
871 inc_page_trap_count();
872 }
873
874 ThreadSafepointState* state = thread->safepoint_state();
875
876 state->handle_polling_page_exception();
877 }
878
879
880 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
881 if (!timeout_error_printed) {
882 timeout_error_printed = true;
883 // Print out the thread info which didn't reach the safepoint for debugging
884 // purposes (useful when there are lots of threads in the debugger).
885 tty->cr();
886 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
887 if (reason == _spinning_timeout) {
888 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
889 } else if (reason == _blocking_timeout) {
890 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
891 }
892
893 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
894 ThreadSafepointState *cur_state;
895 ResourceMark rm;
896 for(JavaThread *cur_thread = Threads::first(); cur_thread;
897 cur_thread = cur_thread->next()) {
898 cur_state = cur_thread->safepoint_state();
899
900 if (cur_thread->thread_state() != _thread_blocked &&
901 ((reason == _spinning_timeout && cur_state->is_running()) ||
902 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
903 tty->print("# ");
904 cur_thread->print();
905 tty->cr();
906 }
907 }
908 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
909 }
910
911 // To debug the long safepoint, specify both DieOnSafepointTimeout &
912 // ShowMessageBoxOnError.
913 if (DieOnSafepointTimeout) {
914 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
915 SafepointTimeoutDelay, VMThread::vm_safepoint_description());
916 }
917 }
918
919
920 // -------------------------------------------------------------------------------------------------------
921 // Implementation of ThreadSafepointState
922
923 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
924 _thread = thread;
925 _type = _running;
926 _has_called_back = false;
927 _at_poll_safepoint = false;
928 }
929
930 void ThreadSafepointState::create(JavaThread *thread) {
931 ThreadSafepointState *state = new ThreadSafepointState(thread);
932 thread->set_safepoint_state(state);
933 }
934
935 void ThreadSafepointState::destroy(JavaThread *thread) {
936 if (thread->safepoint_state()) {
937 delete(thread->safepoint_state());
938 thread->set_safepoint_state(NULL);
939 }
940 }
941
942 void ThreadSafepointState::examine_state_of_thread() {
943 assert(is_running(), "better be running or just have hit safepoint poll");
944
945 JavaThreadState state = _thread->thread_state();
946
947 // Save the state at the start of safepoint processing.
948 _orig_thread_state = state;
949
950 // Check for a thread that is suspended. Note that thread resume tries
951 // to grab the Threads_lock which we own here, so a thread cannot be
952 // resumed during safepoint synchronization.
953
954 // We check to see if this thread is suspended without locking to
955 // avoid deadlocking with a third thread that is waiting for this
956 // thread to be suspended. The third thread can notice the safepoint
957 // that we're trying to start at the beginning of its SR_lock->wait()
958 // call. If that happens, then the third thread will block on the
959 // safepoint while still holding the underlying SR_lock. We won't be
960 // able to get the SR_lock and we'll deadlock.
961 //
962 // We don't need to grab the SR_lock here for two reasons:
963 // 1) The suspend flags are both volatile and are set with an
964 // Atomic::cmpxchg() call so we should see the suspended
965 // state right away.
966 // 2) We're being called from the safepoint polling loop; if
967 // we don't see the suspended state on this iteration, then
968 // we'll come around again.
969 //
970 bool is_suspended = _thread->is_ext_suspended();
971 if (is_suspended) {
972 roll_forward(_at_safepoint);
973 return;
974 }
975
976 // Some JavaThread states have an initial safepoint state of
977 // running, but are actually at a safepoint. We will happily
978 // agree and update the safepoint state here.
979 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
980 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
981 roll_forward(_at_safepoint);
982 return;
983 }
984
985 if (state == _thread_in_vm) {
986 roll_forward(_call_back);
987 return;
988 }
989
990 // All other thread states will continue to run until they
991 // transition and self-block in state _blocked
992 // Safepoint polling in compiled code causes the Java threads to do the same.
993 // Note: new threads may require a malloc so they must be allowed to finish
994
995 assert(is_running(), "examine_state_of_thread on non-running thread");
996 return;
997 }
998
999 // Returns true is thread could not be rolled forward at present position.
1000 void ThreadSafepointState::roll_forward(suspend_type type) {
1001 _type = type;
1002
1003 switch(_type) {
1004 case _at_safepoint:
1005 SafepointSynchronize::signal_thread_at_safepoint();
1006 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
1007 if (_thread->in_critical()) {
1008 // Notice that this thread is in a critical section
1009 SafepointSynchronize::increment_jni_active_count();
1010 }
1011 break;
1012
1013 case _call_back:
1014 set_has_called_back(false);
1015 break;
1016
1017 case _running:
1018 default:
1019 ShouldNotReachHere();
1020 }
1021 }
1022
1023 void ThreadSafepointState::restart() {
1024 switch(type()) {
1025 case _at_safepoint:
1026 case _call_back:
1027 break;
1028
1029 case _running:
1030 default:
1031 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
1032 p2i(_thread), _type);
1033 _thread->print();
1034 ShouldNotReachHere();
1035 }
1036 _type = _running;
1037 set_has_called_back(false);
1038 }
1039
1040
1041 void ThreadSafepointState::print_on(outputStream *st) const {
1042 const char *s = NULL;
1043
1044 switch(_type) {
1045 case _running : s = "_running"; break;
1046 case _at_safepoint : s = "_at_safepoint"; break;
1047 case _call_back : s = "_call_back"; break;
1048 default:
1049 ShouldNotReachHere();
1050 }
1051
1052 st->print_cr("Thread: " INTPTR_FORMAT
1053 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1054 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
1055 _at_poll_safepoint);
1056
1057 _thread->print_thread_state_on(st);
1058 }
1059
1060 // ---------------------------------------------------------------------------------------------------------------------
1061
1062 // Block the thread at the safepoint poll or poll return.
1063 void ThreadSafepointState::handle_polling_page_exception() {
1064
1065 // Check state. block() will set thread state to thread_in_vm which will
1066 // cause the safepoint state _type to become _call_back.
1067 assert(type() == ThreadSafepointState::_running,
1068 "polling page exception on thread not running state");
1069
1070 // Step 1: Find the nmethod from the return address
1071 if (ShowSafepointMsgs && Verbose) {
1072 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
1073 }
1074 address real_return_addr = thread()->saved_exception_pc();
1075
1076 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1077 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1078 CompiledMethod* nm = (CompiledMethod*)cb;
1079
1080 // Find frame of caller
1081 frame stub_fr = thread()->last_frame();
1082 CodeBlob* stub_cb = stub_fr.cb();
1083 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1084 RegisterMap map(thread(), true);
1085 frame caller_fr = stub_fr.sender(&map);
1086
1087 // Should only be poll_return or poll
1088 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1089
1090 // This is a poll immediately before a return. The exception handling code
1091 // has already had the effect of causing the return to occur, so the execution
1092 // will continue immediately after the call. In addition, the oopmap at the
1093 // return point does not mark the return value as an oop (if it is), so
1094 // it needs a handle here to be updated.
1095 if( nm->is_at_poll_return(real_return_addr) ) {
1096 // See if return type is an oop.
1097 bool return_oop = nm->method()->is_returning_oop();
1098 Handle return_value;
1099 if (return_oop) {
1100 // The oop result has been saved on the stack together with all
1101 // the other registers. In order to preserve it over GCs we need
1102 // to keep it in a handle.
1103 oop result = caller_fr.saved_oop_result(&map);
1104 assert(result == NULL || result->is_oop(), "must be oop");
1105 return_value = Handle(thread(), result);
1106 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1107 }
1108
1109 // Block the thread
1110 SafepointSynchronize::block(thread());
1111
1112 // restore oop result, if any
1113 if (return_oop) {
1114 caller_fr.set_saved_oop_result(&map, return_value());
1115 }
1116 }
1117
1118 // This is a safepoint poll. Verify the return address and block.
1119 else {
1120 set_at_poll_safepoint(true);
1121
1122 // verify the blob built the "return address" correctly
1123 assert(real_return_addr == caller_fr.pc(), "must match");
1124
1125 // Block the thread
1126 SafepointSynchronize::block(thread());
1127 set_at_poll_safepoint(false);
1128
1129 // If we have a pending async exception deoptimize the frame
1130 // as otherwise we may never deliver it.
1131 if (thread()->has_async_condition()) {
1132 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1133 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1134 }
1135
1136 // If an exception has been installed we must check for a pending deoptimization
1137 // Deoptimize frame if exception has been thrown.
1138
1139 if (thread()->has_pending_exception() ) {
1140 RegisterMap map(thread(), true);
1141 frame caller_fr = stub_fr.sender(&map);
1142 if (caller_fr.is_deoptimized_frame()) {
1143 // The exception patch will destroy registers that are still
1144 // live and will be needed during deoptimization. Defer the
1145 // Async exception should have deferred the exception until the
1146 // next safepoint which will be detected when we get into
1147 // the interpreter so if we have an exception now things
1148 // are messed up.
1149
1150 fatal("Exception installed and deoptimization is pending");
1151 }
1152 }
1153 }
1154 }
1155
1156
1157 //
1158 // Statistics & Instrumentations
1159 //
1160 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1161 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1162 int SafepointSynchronize::_cur_stat_index = 0;
1163 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1164 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1165 jlong SafepointSynchronize::_max_sync_time = 0;
1166 jlong SafepointSynchronize::_max_vmop_time = 0;
1167 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1168
1169 static jlong cleanup_end_time = 0;
1170 static bool need_to_track_page_armed_status = false;
1171 static bool init_done = false;
1172
1173 // Helper method to print the header.
1174 static void print_header() {
1175 // The number of spaces is significant here, and should match the format
1176 // specifiers in print_statistics().
1177
1178 tty->print(" vmop "
1179 "[ threads: total initially_running wait_to_block ]"
1180 "[ time: spin block sync cleanup vmop ] ");
1181
1182 // no page armed status printed out if it is always armed.
1183 if (need_to_track_page_armed_status) {
1184 tty->print("page_armed ");
1185 }
1186
1187 tty->print_cr("page_trap_count");
1188 }
1189
1190 void SafepointSynchronize::deferred_initialize_stat() {
1191 if (init_done) return;
1192
1193 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1194 // be printed right away, in which case, _safepoint_stats will regress to
1195 // a single element array. Otherwise, it is a circular ring buffer with default
1196 // size of PrintSafepointStatisticsCount.
1197 int stats_array_size;
1198 if (PrintSafepointStatisticsTimeout > 0) {
1199 stats_array_size = 1;
1200 PrintSafepointStatistics = true;
1201 } else {
1202 stats_array_size = PrintSafepointStatisticsCount;
1203 }
1204 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1205 * sizeof(SafepointStats), mtInternal);
1206 guarantee(_safepoint_stats != NULL,
1207 "not enough memory for safepoint instrumentation data");
1208
1209 if (DeferPollingPageLoopCount >= 0) {
1210 need_to_track_page_armed_status = true;
1211 }
1212 init_done = true;
1213 }
1214
1215 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1216 assert(init_done, "safepoint statistics array hasn't been initialized");
1217 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1218
1219 spstat->_time_stamp = _ts_of_current_safepoint;
1220
1221 VM_Operation *op = VMThread::vm_operation();
1222 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1223 if (op != NULL) {
1224 _safepoint_reasons[spstat->_vmop_type]++;
1225 }
1226
1227 spstat->_nof_total_threads = nof_threads;
1228 spstat->_nof_initial_running_threads = nof_running;
1229 spstat->_nof_threads_hit_page_trap = 0;
1230
1231 // Records the start time of spinning. The real time spent on spinning
1232 // will be adjusted when spin is done. Same trick is applied for time
1233 // spent on waiting for threads to block.
1234 if (nof_running != 0) {
1235 spstat->_time_to_spin = os::javaTimeNanos();
1236 } else {
1237 spstat->_time_to_spin = 0;
1238 }
1239 }
1240
1241 void SafepointSynchronize::update_statistics_on_spin_end() {
1242 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1243
1244 jlong cur_time = os::javaTimeNanos();
1245
1246 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1247 if (spstat->_nof_initial_running_threads != 0) {
1248 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1249 }
1250
1251 if (need_to_track_page_armed_status) {
1252 spstat->_page_armed = (PageArmed == 1);
1253 }
1254
1255 // Records the start time of waiting for to block. Updated when block is done.
1256 if (_waiting_to_block != 0) {
1257 spstat->_time_to_wait_to_block = cur_time;
1258 } else {
1259 spstat->_time_to_wait_to_block = 0;
1260 }
1261 }
1262
1263 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1264 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1265
1266 if (spstat->_nof_threads_wait_to_block != 0) {
1267 spstat->_time_to_wait_to_block = end_time -
1268 spstat->_time_to_wait_to_block;
1269 }
1270
1271 // Records the end time of sync which will be used to calculate the total
1272 // vm operation time. Again, the real time spending in syncing will be deducted
1273 // from the start of the sync time later when end_statistics is called.
1274 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1275 if (spstat->_time_to_sync > _max_sync_time) {
1276 _max_sync_time = spstat->_time_to_sync;
1277 }
1278
1279 spstat->_time_to_do_cleanups = end_time;
1280 }
1281
1282 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1283 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1284
1285 // Record how long spent in cleanup tasks.
1286 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1287
1288 cleanup_end_time = end_time;
1289 }
1290
1291 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1292 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1293
1294 // Update the vm operation time.
1295 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1296 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1297 _max_vmop_time = spstat->_time_to_exec_vmop;
1298 }
1299 // Only the sync time longer than the specified
1300 // PrintSafepointStatisticsTimeout will be printed out right away.
1301 // By default, it is -1 meaning all samples will be put into the list.
1302 if ( PrintSafepointStatisticsTimeout > 0) {
1303 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1304 print_statistics();
1305 }
1306 } else {
1307 // The safepoint statistics will be printed out when the _safepoin_stats
1308 // array fills up.
1309 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1310 print_statistics();
1311 _cur_stat_index = 0;
1312 } else {
1313 _cur_stat_index++;
1314 }
1315 }
1316 }
1317
1318 void SafepointSynchronize::print_statistics() {
1319 for (int index = 0; index <= _cur_stat_index; index++) {
1320 if (index % 30 == 0) {
1321 print_header();
1322 }
1323 SafepointStats* sstats = &_safepoint_stats[index];
1324 tty->print("%8.3f: ", sstats->_time_stamp);
1325 tty->print("%-30s [ "
1326 INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " "
1327 "]",
1328 (sstats->_vmop_type == -1 ? "no vm operation" : VM_Operation::name(sstats->_vmop_type)),
1329 sstats->_nof_total_threads,
1330 sstats->_nof_initial_running_threads,
1331 sstats->_nof_threads_wait_to_block);
1332 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1333 tty->print("[ "
1334 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1335 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1336 INT64_FORMAT_W(7) " ] ",
1337 sstats->_time_to_spin / MICROUNITS,
1338 sstats->_time_to_wait_to_block / MICROUNITS,
1339 sstats->_time_to_sync / MICROUNITS,
1340 sstats->_time_to_do_cleanups / MICROUNITS,
1341 sstats->_time_to_exec_vmop / MICROUNITS);
1342
1343 if (need_to_track_page_armed_status) {
1344 tty->print(INT32_FORMAT_W(10) " ", sstats->_page_armed);
1345 }
1346 tty->print_cr(INT32_FORMAT_W(15) " ", sstats->_nof_threads_hit_page_trap);
1347 }
1348 }
1349
1350 // This method will be called when VM exits. It will first call
1351 // print_statistics to print out the rest of the sampling. Then
1352 // it tries to summarize the sampling.
1353 void SafepointSynchronize::print_stat_on_exit() {
1354 if (_safepoint_stats == NULL) return;
1355
1356 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1357
1358 // During VM exit, end_statistics may not get called and in that
1359 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1360 // don't print it out.
1361 // Approximate the vm op time.
1362 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1363 os::javaTimeNanos() - cleanup_end_time;
1364
1365 if ( PrintSafepointStatisticsTimeout < 0 ||
1366 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1367 print_statistics();
1368 }
1369 tty->cr();
1370
1371 // Print out polling page sampling status.
1372 if (!need_to_track_page_armed_status) {
1373 tty->print_cr("Polling page always armed");
1374 } else {
1375 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
1376 DeferPollingPageLoopCount);
1377 }
1378
1379 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1380 if (_safepoint_reasons[index] != 0) {
1381 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1382 _safepoint_reasons[index]);
1383 }
1384 }
1385
1386 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1387 _coalesced_vmop_count);
1388 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1389 _max_sync_time / MICROUNITS);
1390 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1391 INT64_FORMAT_W(5) " ms",
1392 _max_vmop_time / MICROUNITS);
1393 }
1394
1395 // ------------------------------------------------------------------------------------------------
1396 // Non-product code
1397
1398 #ifndef PRODUCT
1399
1400 void SafepointSynchronize::print_state() {
1401 if (_state == _not_synchronized) {
1402 tty->print_cr("not synchronized");
1403 } else if (_state == _synchronizing || _state == _synchronized) {
1404 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1405 "synchronized");
1406
1407 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1408 cur->safepoint_state()->print();
1409 }
1410 }
1411 }
1412
1413 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1414 if (ShowSafepointMsgs) {
1415 va_list ap;
1416 va_start(ap, format);
1417 tty->vprint_cr(format, ap);
1418 va_end(ap);
1419 }
1420 }
1421
1422 #endif // !PRODUCT