1 /*
2 * Copyright (c) 1997, 2016, 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 VM_Operation *op = VMThread::vm_operation();
400 log_debug(safepoint)("Entering safepoint region: %s",
401 (op != NULL) ? op->name() : "no vm operation");
402 }
403
404 RuntimeService::record_safepoint_synchronized();
405 if (PrintSafepointStatistics) {
406 update_statistics_on_sync_end(os::javaTimeNanos());
407 }
408
409 // Call stuff that needs to be run when a safepoint is just about to be completed
410 {
411 EventSafepointCleanup cleanup_event;
412 do_cleanup_tasks();
413 if (cleanup_event.should_commit()) {
414 cleanup_event.set_safepointId(safepoint_counter());
415 cleanup_event.commit();
416 }
417 }
418
419 if (PrintSafepointStatistics) {
420 // Record how much time spend on the above cleanup tasks
421 update_statistics_on_cleanup_end(os::javaTimeNanos());
422 }
423 if (begin_event.should_commit()) {
424 begin_event.set_safepointId(safepoint_counter());
425 begin_event.set_totalThreadCount(nof_threads);
426 begin_event.set_jniCriticalThreadCount(_current_jni_active_count);
427 begin_event.commit();
428 }
429 }
430
431 // Wake up all threads, so they are ready to resume execution after the safepoint
432 // operation has been carried out
433 void SafepointSynchronize::end() {
434 EventSafepointEnd event;
435 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id"
436
437 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
438 assert((_safepoint_counter & 0x1) == 1, "must be odd");
439 _safepoint_counter ++;
440 // memory fence isn't required here since an odd _safepoint_counter
441 // value can do no harm and a fence is issued below anyway.
442
443 DEBUG_ONLY(Thread* myThread = Thread::current();)
444 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
445
446 if (PrintSafepointStatistics) {
447 end_statistics(os::javaTimeNanos());
448 }
449
450 #ifdef ASSERT
451 // A pending_exception cannot be installed during a safepoint. The threads
452 // may install an async exception after they come back from a safepoint into
453 // pending_exception after they unblock. But that should happen later.
454 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
455 assert (!(cur->has_pending_exception() &&
456 cur->safepoint_state()->is_at_poll_safepoint()),
457 "safepoint installed a pending exception");
458 }
459 #endif // ASSERT
460
461 if (PageArmed) {
462 // Make polling safepoint aware
463 os::make_polling_page_readable();
464 PageArmed = 0 ;
465 }
466
467 // Remove safepoint check from interpreter
468 Interpreter::ignore_safepoints();
469
470 {
471 MutexLocker mu(Safepoint_lock);
472
473 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
474
475 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
476 // when they get restarted.
477 _state = _not_synchronized;
478 OrderAccess::fence();
479
480 log_debug(safepoint)("Leaving safepoint region");
481
482 // Start suspended threads
483 for(JavaThread *current = Threads::first(); current; current = current->next()) {
484 // A problem occurring on Solaris is when attempting to restart threads
485 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
486 // to the next one (since it has been running the longest). We then have
487 // to wait for a cpu to become available before we can continue restarting
488 // threads.
489 // FIXME: This causes the performance of the VM to degrade when active and with
490 // large numbers of threads. Apparently this is due to the synchronous nature
491 // of suspending threads.
492 //
493 // TODO-FIXME: the comments above are vestigial and no longer apply.
494 // Furthermore, using solaris' schedctl in this particular context confers no benefit
495 if (VMThreadHintNoPreempt) {
496 os::hint_no_preempt();
497 }
498 ThreadSafepointState* cur_state = current->safepoint_state();
499 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
500 cur_state->restart();
501 assert(cur_state->is_running(), "safepoint state has not been reset");
502 }
503
504 RuntimeService::record_safepoint_end();
505
506 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
507 // blocked in signal_thread_blocked
508 Threads_lock->unlock();
509
510 }
511 #if INCLUDE_ALL_GCS
512 // If there are any concurrent GC threads resume them.
513 if (UseConcMarkSweepGC) {
514 ConcurrentMarkSweepThread::desynchronize(false);
515 } else if (UseG1GC) {
516 SuspendibleThreadSet::desynchronize();
517 }
518 #endif // INCLUDE_ALL_GCS
519 // record this time so VMThread can keep track how much time has elapsed
520 // since last safepoint.
521 _end_of_last_safepoint = os::javaTimeMillis();
522
523 if (event.should_commit()) {
524 event.set_safepointId(safepoint_id);
525 event.commit();
526 }
527 }
528
529 bool SafepointSynchronize::is_cleanup_needed() {
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 // Various cleaning tasks that should be done periodically at safepoints
544 void SafepointSynchronize::do_cleanup_tasks() {
545 {
546 const char* name = "deflating idle monitors";
547 EventSafepointCleanupTask event;
548 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
549 ObjectSynchronizer::deflate_idle_monitors();
550 event_safepoint_cleanup_task_commit(event, name);
551 }
552
553 {
554 const char* name = "updating inline caches";
555 EventSafepointCleanupTask event;
556 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
557 InlineCacheBuffer::update_inline_caches();
558 event_safepoint_cleanup_task_commit(event, name);
559 }
560 {
561 const char* name = "compilation policy safepoint handler";
562 EventSafepointCleanupTask event;
563 TraceTime timer("compilation policy safepoint handler", TRACETIME_LOG(Info, safepoint, cleanup));
564 CompilationPolicy::policy()->do_safepoint_work();
565 event_safepoint_cleanup_task_commit(event, name);
566 }
567
568 {
569 const char* name = "mark nmethods";
570 EventSafepointCleanupTask event;
571 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
572 NMethodSweeper::mark_active_nmethods();
573 event_safepoint_cleanup_task_commit(event, name);
574 }
575
576 if (SymbolTable::needs_rehashing()) {
577 const char* name = "rehashing symbol table";
578 EventSafepointCleanupTask event;
579 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
580 SymbolTable::rehash_table();
581 event_safepoint_cleanup_task_commit(event, name);
582 }
583
584 if (StringTable::needs_rehashing()) {
585 const char* name = "rehashing string table";
586 EventSafepointCleanupTask event;
587 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
588 StringTable::rehash_table();
589 event_safepoint_cleanup_task_commit(event, name);
590 }
591
592 {
593 // CMS delays purging the CLDG until the beginning of the next safepoint and to
594 // make sure concurrent sweep is done
595 const char* name = "purging class loader data graph";
596 EventSafepointCleanupTask event;
597 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
598 ClassLoaderDataGraph::purge_if_needed();
599 event_safepoint_cleanup_task_commit(event, name);
600 }
601 }
602
603
604 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
605 switch(state) {
606 case _thread_in_native:
607 // native threads are safe if they have no java stack or have walkable stack
608 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
609
610 // blocked threads should have already have walkable stack
611 case _thread_blocked:
612 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
613 return true;
614
615 default:
616 return false;
617 }
618 }
619
620
621 // See if the thread is running inside a lazy critical native and
622 // update the thread critical count if so. Also set a suspend flag to
623 // cause the native wrapper to return into the JVM to do the unlock
624 // once the native finishes.
625 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
626 if (state == _thread_in_native &&
627 thread->has_last_Java_frame() &&
628 thread->frame_anchor()->walkable()) {
629 // This thread might be in a critical native nmethod so look at
630 // the top of the stack and increment the critical count if it
631 // is.
632 frame wrapper_frame = thread->last_frame();
633 CodeBlob* stub_cb = wrapper_frame.cb();
634 if (stub_cb != NULL &&
635 stub_cb->is_nmethod() &&
636 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
637 // A thread could potentially be in a critical native across
638 // more than one safepoint, so only update the critical state on
639 // the first one. When it returns it will perform the unlock.
640 if (!thread->do_critical_native_unlock()) {
641 #ifdef ASSERT
642 if (!thread->in_critical()) {
643 GCLocker::increment_debug_jni_lock_count();
644 }
645 #endif
646 thread->enter_critical();
647 // Make sure the native wrapper calls back on return to
648 // perform the needed critical unlock.
649 thread->set_critical_native_unlock();
650 }
651 }
652 }
653 }
654
655
656
657 // -------------------------------------------------------------------------------------------------------
658 // Implementation of Safepoint callback point
659
660 void SafepointSynchronize::block(JavaThread *thread) {
661 assert(thread != NULL, "thread must be set");
662 assert(thread->is_Java_thread(), "not a Java thread");
663
664 // Threads shouldn't block if they are in the middle of printing, but...
665 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
666
667 // Only bail from the block() call if the thread is gone from the
668 // thread list; starting to exit should still block.
669 if (thread->is_terminated()) {
670 // block current thread if we come here from native code when VM is gone
671 thread->block_if_vm_exited();
672
673 // otherwise do nothing
674 return;
675 }
676
677 JavaThreadState state = thread->thread_state();
678 thread->frame_anchor()->make_walkable(thread);
679
680 // Check that we have a valid thread_state at this point
681 switch(state) {
682 case _thread_in_vm_trans:
683 case _thread_in_Java: // From compiled code
684
685 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
686 // we pretend we are still in the VM.
687 thread->set_thread_state(_thread_in_vm);
688
689 if (is_synchronizing()) {
690 Atomic::inc (&TryingToBlock) ;
691 }
692
693 // We will always be holding the Safepoint_lock when we are examine the state
694 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
695 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
696 Safepoint_lock->lock_without_safepoint_check();
697 if (is_synchronizing()) {
698 // Decrement the number of threads to wait for and signal vm thread
699 assert(_waiting_to_block > 0, "sanity check");
700 _waiting_to_block--;
701 thread->safepoint_state()->set_has_called_back(true);
702
703 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
704 if (thread->in_critical()) {
705 // Notice that this thread is in a critical section
706 increment_jni_active_count();
707 }
708
709 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
710 if (_waiting_to_block == 0) {
711 Safepoint_lock->notify_all();
712 }
713 }
714
715 // We transition the thread to state _thread_blocked here, but
716 // we can't do our usual check for external suspension and then
717 // self-suspend after the lock_without_safepoint_check() call
718 // below because we are often called during transitions while
719 // we hold different locks. That would leave us suspended while
720 // holding a resource which results in deadlocks.
721 thread->set_thread_state(_thread_blocked);
722 Safepoint_lock->unlock();
723
724 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
725 // the entire safepoint, the threads will all line up here during the safepoint.
726 Threads_lock->lock_without_safepoint_check();
727 // restore original state. This is important if the thread comes from compiled code, so it
728 // will continue to execute with the _thread_in_Java state.
729 thread->set_thread_state(state);
730 Threads_lock->unlock();
731 break;
732
733 case _thread_in_native_trans:
734 case _thread_blocked_trans:
735 case _thread_new_trans:
736 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
737 thread->print_thread_state();
738 fatal("Deadlock in safepoint code. "
739 "Should have called back to the VM before blocking.");
740 }
741
742 // We transition the thread to state _thread_blocked here, but
743 // we can't do our usual check for external suspension and then
744 // self-suspend after the lock_without_safepoint_check() call
745 // below because we are often called during transitions while
746 // we hold different locks. That would leave us suspended while
747 // holding a resource which results in deadlocks.
748 thread->set_thread_state(_thread_blocked);
749
750 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
751 // the safepoint code might still be waiting for it to block. We need to change the state here,
752 // so it can see that it is at a safepoint.
753
754 // Block until the safepoint operation is completed.
755 Threads_lock->lock_without_safepoint_check();
756
757 // Restore state
758 thread->set_thread_state(state);
759
760 Threads_lock->unlock();
761 break;
762
763 default:
764 fatal("Illegal threadstate encountered: %d", state);
765 }
766
767 // Check for pending. async. exceptions or suspends - except if the
768 // thread was blocked inside the VM. has_special_runtime_exit_condition()
769 // is called last since it grabs a lock and we only want to do that when
770 // we must.
771 //
772 // Note: we never deliver an async exception at a polling point as the
773 // compiler may not have an exception handler for it. The polling
774 // code will notice the async and deoptimize and the exception will
775 // be delivered. (Polling at a return point is ok though). Sure is
776 // a lot of bother for a deprecated feature...
777 //
778 // We don't deliver an async exception if the thread state is
779 // _thread_in_native_trans so JNI functions won't be called with
780 // a surprising pending exception. If the thread state is going back to java,
781 // async exception is checked in check_special_condition_for_native_trans().
782
783 if (state != _thread_blocked_trans &&
784 state != _thread_in_vm_trans &&
785 thread->has_special_runtime_exit_condition()) {
786 thread->handle_special_runtime_exit_condition(
787 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
788 }
789 }
790
791 // ------------------------------------------------------------------------------------------------------
792 // Exception handlers
793
794
795 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
796 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
797 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
798 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
799
800 if (ShowSafepointMsgs) {
801 tty->print("handle_polling_page_exception: ");
802 }
803
804 if (PrintSafepointStatistics) {
805 inc_page_trap_count();
806 }
807
808 ThreadSafepointState* state = thread->safepoint_state();
809
810 state->handle_polling_page_exception();
811 }
812
813
814 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
815 if (!timeout_error_printed) {
816 timeout_error_printed = true;
817 // Print out the thread info which didn't reach the safepoint for debugging
818 // purposes (useful when there are lots of threads in the debugger).
819 tty->cr();
820 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
821 if (reason == _spinning_timeout) {
822 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
823 } else if (reason == _blocking_timeout) {
824 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
825 }
826
827 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
828 ThreadSafepointState *cur_state;
829 ResourceMark rm;
830 for(JavaThread *cur_thread = Threads::first(); cur_thread;
831 cur_thread = cur_thread->next()) {
832 cur_state = cur_thread->safepoint_state();
833
834 if (cur_thread->thread_state() != _thread_blocked &&
835 ((reason == _spinning_timeout && cur_state->is_running()) ||
836 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
837 tty->print("# ");
838 cur_thread->print();
839 tty->cr();
840 }
841 }
842 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
843 }
844
845 // To debug the long safepoint, specify both DieOnSafepointTimeout &
846 // ShowMessageBoxOnError.
847 if (DieOnSafepointTimeout) {
848 VM_Operation *op = VMThread::vm_operation();
849 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
850 SafepointTimeoutDelay,
851 op != NULL ? op->name() : "no vm operation");
852 }
853 }
854
855
856 // -------------------------------------------------------------------------------------------------------
857 // Implementation of ThreadSafepointState
858
859 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
860 _thread = thread;
861 _type = _running;
862 _has_called_back = false;
863 _at_poll_safepoint = false;
864 }
865
866 void ThreadSafepointState::create(JavaThread *thread) {
867 ThreadSafepointState *state = new ThreadSafepointState(thread);
868 thread->set_safepoint_state(state);
869 }
870
871 void ThreadSafepointState::destroy(JavaThread *thread) {
872 if (thread->safepoint_state()) {
873 delete(thread->safepoint_state());
874 thread->set_safepoint_state(NULL);
875 }
876 }
877
878 void ThreadSafepointState::examine_state_of_thread() {
879 assert(is_running(), "better be running or just have hit safepoint poll");
880
881 JavaThreadState state = _thread->thread_state();
882
883 // Save the state at the start of safepoint processing.
884 _orig_thread_state = state;
885
886 // Check for a thread that is suspended. Note that thread resume tries
887 // to grab the Threads_lock which we own here, so a thread cannot be
888 // resumed during safepoint synchronization.
889
890 // We check to see if this thread is suspended without locking to
891 // avoid deadlocking with a third thread that is waiting for this
892 // thread to be suspended. The third thread can notice the safepoint
893 // that we're trying to start at the beginning of its SR_lock->wait()
894 // call. If that happens, then the third thread will block on the
895 // safepoint while still holding the underlying SR_lock. We won't be
896 // able to get the SR_lock and we'll deadlock.
897 //
898 // We don't need to grab the SR_lock here for two reasons:
899 // 1) The suspend flags are both volatile and are set with an
900 // Atomic::cmpxchg() call so we should see the suspended
901 // state right away.
902 // 2) We're being called from the safepoint polling loop; if
903 // we don't see the suspended state on this iteration, then
904 // we'll come around again.
905 //
906 bool is_suspended = _thread->is_ext_suspended();
907 if (is_suspended) {
908 roll_forward(_at_safepoint);
909 return;
910 }
911
912 // Some JavaThread states have an initial safepoint state of
913 // running, but are actually at a safepoint. We will happily
914 // agree and update the safepoint state here.
915 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
916 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
917 roll_forward(_at_safepoint);
918 return;
919 }
920
921 if (state == _thread_in_vm) {
922 roll_forward(_call_back);
923 return;
924 }
925
926 // All other thread states will continue to run until they
927 // transition and self-block in state _blocked
928 // Safepoint polling in compiled code causes the Java threads to do the same.
929 // Note: new threads may require a malloc so they must be allowed to finish
930
931 assert(is_running(), "examine_state_of_thread on non-running thread");
932 return;
933 }
934
935 // Returns true is thread could not be rolled forward at present position.
936 void ThreadSafepointState::roll_forward(suspend_type type) {
937 _type = type;
938
939 switch(_type) {
940 case _at_safepoint:
941 SafepointSynchronize::signal_thread_at_safepoint();
942 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
943 if (_thread->in_critical()) {
944 // Notice that this thread is in a critical section
945 SafepointSynchronize::increment_jni_active_count();
946 }
947 break;
948
949 case _call_back:
950 set_has_called_back(false);
951 break;
952
953 case _running:
954 default:
955 ShouldNotReachHere();
956 }
957 }
958
959 void ThreadSafepointState::restart() {
960 switch(type()) {
961 case _at_safepoint:
962 case _call_back:
963 break;
964
965 case _running:
966 default:
967 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
968 p2i(_thread), _type);
969 _thread->print();
970 ShouldNotReachHere();
971 }
972 _type = _running;
973 set_has_called_back(false);
974 }
975
976
977 void ThreadSafepointState::print_on(outputStream *st) const {
978 const char *s = NULL;
979
980 switch(_type) {
981 case _running : s = "_running"; break;
982 case _at_safepoint : s = "_at_safepoint"; break;
983 case _call_back : s = "_call_back"; break;
984 default:
985 ShouldNotReachHere();
986 }
987
988 st->print_cr("Thread: " INTPTR_FORMAT
989 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
990 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
991 _at_poll_safepoint);
992
993 _thread->print_thread_state_on(st);
994 }
995
996 // ---------------------------------------------------------------------------------------------------------------------
997
998 // Block the thread at the safepoint poll or poll return.
999 void ThreadSafepointState::handle_polling_page_exception() {
1000
1001 // Check state. block() will set thread state to thread_in_vm which will
1002 // cause the safepoint state _type to become _call_back.
1003 assert(type() == ThreadSafepointState::_running,
1004 "polling page exception on thread not running state");
1005
1006 // Step 1: Find the nmethod from the return address
1007 if (ShowSafepointMsgs && Verbose) {
1008 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
1009 }
1010 address real_return_addr = thread()->saved_exception_pc();
1011
1012 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1013 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1014 CompiledMethod* nm = (CompiledMethod*)cb;
1015
1016 // Find frame of caller
1017 frame stub_fr = thread()->last_frame();
1018 CodeBlob* stub_cb = stub_fr.cb();
1019 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1020 RegisterMap map(thread(), true);
1021 frame caller_fr = stub_fr.sender(&map);
1022
1023 // Should only be poll_return or poll
1024 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1025
1026 // This is a poll immediately before a return. The exception handling code
1027 // has already had the effect of causing the return to occur, so the execution
1028 // will continue immediately after the call. In addition, the oopmap at the
1029 // return point does not mark the return value as an oop (if it is), so
1030 // it needs a handle here to be updated.
1031 if( nm->is_at_poll_return(real_return_addr) ) {
1032 // See if return type is an oop.
1033 bool return_oop = nm->method()->is_returning_oop();
1034 Handle return_value;
1035 if (return_oop) {
1036 // The oop result has been saved on the stack together with all
1037 // the other registers. In order to preserve it over GCs we need
1038 // to keep it in a handle.
1039 oop result = caller_fr.saved_oop_result(&map);
1040 assert(result == NULL || result->is_oop(), "must be oop");
1041 return_value = Handle(thread(), result);
1042 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1043 }
1044
1045 // Block the thread
1046 SafepointSynchronize::block(thread());
1047
1048 // restore oop result, if any
1049 if (return_oop) {
1050 caller_fr.set_saved_oop_result(&map, return_value());
1051 }
1052 }
1053
1054 // This is a safepoint poll. Verify the return address and block.
1055 else {
1056 set_at_poll_safepoint(true);
1057
1058 // verify the blob built the "return address" correctly
1059 assert(real_return_addr == caller_fr.pc(), "must match");
1060
1061 // Block the thread
1062 SafepointSynchronize::block(thread());
1063 set_at_poll_safepoint(false);
1064
1065 // If we have a pending async exception deoptimize the frame
1066 // as otherwise we may never deliver it.
1067 if (thread()->has_async_condition()) {
1068 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1069 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1070 }
1071
1072 // If an exception has been installed we must check for a pending deoptimization
1073 // Deoptimize frame if exception has been thrown.
1074
1075 if (thread()->has_pending_exception() ) {
1076 RegisterMap map(thread(), true);
1077 frame caller_fr = stub_fr.sender(&map);
1078 if (caller_fr.is_deoptimized_frame()) {
1079 // The exception patch will destroy registers that are still
1080 // live and will be needed during deoptimization. Defer the
1081 // Async exception should have deferred the exception until the
1082 // next safepoint which will be detected when we get into
1083 // the interpreter so if we have an exception now things
1084 // are messed up.
1085
1086 fatal("Exception installed and deoptimization is pending");
1087 }
1088 }
1089 }
1090 }
1091
1092
1093 //
1094 // Statistics & Instrumentations
1095 //
1096 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1097 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1098 int SafepointSynchronize::_cur_stat_index = 0;
1099 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1100 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1101 jlong SafepointSynchronize::_max_sync_time = 0;
1102 jlong SafepointSynchronize::_max_vmop_time = 0;
1103 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1104
1105 static jlong cleanup_end_time = 0;
1106 static bool need_to_track_page_armed_status = false;
1107 static bool init_done = false;
1108
1109 // Helper method to print the header.
1110 static void print_header() {
1111 tty->print(" vmop "
1112 "[threads: total initially_running wait_to_block] ");
1113 tty->print("[time: spin block sync cleanup vmop] ");
1114
1115 // no page armed status printed out if it is always armed.
1116 if (need_to_track_page_armed_status) {
1117 tty->print("page_armed ");
1118 }
1119
1120 tty->print_cr("page_trap_count");
1121 }
1122
1123 void SafepointSynchronize::deferred_initialize_stat() {
1124 if (init_done) return;
1125
1126 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1127 // be printed right away, in which case, _safepoint_stats will regress to
1128 // a single element array. Otherwise, it is a circular ring buffer with default
1129 // size of PrintSafepointStatisticsCount.
1130 int stats_array_size;
1131 if (PrintSafepointStatisticsTimeout > 0) {
1132 stats_array_size = 1;
1133 PrintSafepointStatistics = true;
1134 } else {
1135 stats_array_size = PrintSafepointStatisticsCount;
1136 }
1137 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1138 * sizeof(SafepointStats), mtInternal);
1139 guarantee(_safepoint_stats != NULL,
1140 "not enough memory for safepoint instrumentation data");
1141
1142 if (DeferPollingPageLoopCount >= 0) {
1143 need_to_track_page_armed_status = true;
1144 }
1145 init_done = true;
1146 }
1147
1148 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1149 assert(init_done, "safepoint statistics array hasn't been initialized");
1150 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1151
1152 spstat->_time_stamp = _ts_of_current_safepoint;
1153
1154 VM_Operation *op = VMThread::vm_operation();
1155 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1156 if (op != NULL) {
1157 _safepoint_reasons[spstat->_vmop_type]++;
1158 }
1159
1160 spstat->_nof_total_threads = nof_threads;
1161 spstat->_nof_initial_running_threads = nof_running;
1162 spstat->_nof_threads_hit_page_trap = 0;
1163
1164 // Records the start time of spinning. The real time spent on spinning
1165 // will be adjusted when spin is done. Same trick is applied for time
1166 // spent on waiting for threads to block.
1167 if (nof_running != 0) {
1168 spstat->_time_to_spin = os::javaTimeNanos();
1169 } else {
1170 spstat->_time_to_spin = 0;
1171 }
1172 }
1173
1174 void SafepointSynchronize::update_statistics_on_spin_end() {
1175 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1176
1177 jlong cur_time = os::javaTimeNanos();
1178
1179 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1180 if (spstat->_nof_initial_running_threads != 0) {
1181 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1182 }
1183
1184 if (need_to_track_page_armed_status) {
1185 spstat->_page_armed = (PageArmed == 1);
1186 }
1187
1188 // Records the start time of waiting for to block. Updated when block is done.
1189 if (_waiting_to_block != 0) {
1190 spstat->_time_to_wait_to_block = cur_time;
1191 } else {
1192 spstat->_time_to_wait_to_block = 0;
1193 }
1194 }
1195
1196 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1197 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1198
1199 if (spstat->_nof_threads_wait_to_block != 0) {
1200 spstat->_time_to_wait_to_block = end_time -
1201 spstat->_time_to_wait_to_block;
1202 }
1203
1204 // Records the end time of sync which will be used to calculate the total
1205 // vm operation time. Again, the real time spending in syncing will be deducted
1206 // from the start of the sync time later when end_statistics is called.
1207 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1208 if (spstat->_time_to_sync > _max_sync_time) {
1209 _max_sync_time = spstat->_time_to_sync;
1210 }
1211
1212 spstat->_time_to_do_cleanups = end_time;
1213 }
1214
1215 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1216 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1217
1218 // Record how long spent in cleanup tasks.
1219 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1220
1221 cleanup_end_time = end_time;
1222 }
1223
1224 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1225 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1226
1227 // Update the vm operation time.
1228 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1229 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1230 _max_vmop_time = spstat->_time_to_exec_vmop;
1231 }
1232 // Only the sync time longer than the specified
1233 // PrintSafepointStatisticsTimeout will be printed out right away.
1234 // By default, it is -1 meaning all samples will be put into the list.
1235 if ( PrintSafepointStatisticsTimeout > 0) {
1236 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1237 print_statistics();
1238 }
1239 } else {
1240 // The safepoint statistics will be printed out when the _safepoin_stats
1241 // array fills up.
1242 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1243 print_statistics();
1244 _cur_stat_index = 0;
1245 } else {
1246 _cur_stat_index++;
1247 }
1248 }
1249 }
1250
1251 void SafepointSynchronize::print_statistics() {
1252 SafepointStats* sstats = _safepoint_stats;
1253
1254 for (int index = 0; index <= _cur_stat_index; index++) {
1255 if (index % 30 == 0) {
1256 print_header();
1257 }
1258 sstats = &_safepoint_stats[index];
1259 tty->print("%.3f: ", sstats->_time_stamp);
1260 tty->print("%-26s ["
1261 INT32_FORMAT_W(8) INT32_FORMAT_W(11) INT32_FORMAT_W(15)
1262 " ] ",
1263 sstats->_vmop_type == -1 ? "no vm operation" :
1264 VM_Operation::name(sstats->_vmop_type),
1265 sstats->_nof_total_threads,
1266 sstats->_nof_initial_running_threads,
1267 sstats->_nof_threads_wait_to_block);
1268 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1269 tty->print(" ["
1270 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1271 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1272 INT64_FORMAT_W(6) " ] ",
1273 sstats->_time_to_spin / MICROUNITS,
1274 sstats->_time_to_wait_to_block / MICROUNITS,
1275 sstats->_time_to_sync / MICROUNITS,
1276 sstats->_time_to_do_cleanups / MICROUNITS,
1277 sstats->_time_to_exec_vmop / MICROUNITS);
1278
1279 if (need_to_track_page_armed_status) {
1280 tty->print(INT32_FORMAT " ", sstats->_page_armed);
1281 }
1282 tty->print_cr(INT32_FORMAT " ", sstats->_nof_threads_hit_page_trap);
1283 }
1284 }
1285
1286 // This method will be called when VM exits. It will first call
1287 // print_statistics to print out the rest of the sampling. Then
1288 // it tries to summarize the sampling.
1289 void SafepointSynchronize::print_stat_on_exit() {
1290 if (_safepoint_stats == NULL) return;
1291
1292 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1293
1294 // During VM exit, end_statistics may not get called and in that
1295 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1296 // don't print it out.
1297 // Approximate the vm op time.
1298 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1299 os::javaTimeNanos() - cleanup_end_time;
1300
1301 if ( PrintSafepointStatisticsTimeout < 0 ||
1302 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1303 print_statistics();
1304 }
1305 tty->cr();
1306
1307 // Print out polling page sampling status.
1308 if (!need_to_track_page_armed_status) {
1309 tty->print_cr("Polling page always armed");
1310 } else {
1311 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
1312 DeferPollingPageLoopCount);
1313 }
1314
1315 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1316 if (_safepoint_reasons[index] != 0) {
1317 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1318 _safepoint_reasons[index]);
1319 }
1320 }
1321
1322 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1323 _coalesced_vmop_count);
1324 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1325 _max_sync_time / MICROUNITS);
1326 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1327 INT64_FORMAT_W(5) " ms",
1328 _max_vmop_time / MICROUNITS);
1329 }
1330
1331 // ------------------------------------------------------------------------------------------------
1332 // Non-product code
1333
1334 #ifndef PRODUCT
1335
1336 void SafepointSynchronize::print_state() {
1337 if (_state == _not_synchronized) {
1338 tty->print_cr("not synchronized");
1339 } else if (_state == _synchronizing || _state == _synchronized) {
1340 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1341 "synchronized");
1342
1343 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1344 cur->safepoint_state()->print();
1345 }
1346 }
1347 }
1348
1349 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1350 if (ShowSafepointMsgs) {
1351 va_list ap;
1352 va_start(ap, format);
1353 tty->vprint_cr(format, ap);
1354 va_end(ap);
1355 }
1356 }
1357
1358 #endif // !PRODUCT