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 "logging/logStream.hpp"
39 #include "memory/resourceArea.hpp"
40 #include "memory/universe.inline.hpp"
41 #include "oops/oop.inline.hpp"
42 #include "oops/symbol.hpp"
43 #include "runtime/atomic.hpp"
44 #include "runtime/compilationPolicy.hpp"
45 #include "runtime/deoptimization.hpp"
46 #include "runtime/frame.inline.hpp"
47 #include "runtime/interfaceSupport.hpp"
48 #include "runtime/mutexLocker.hpp"
49 #include "runtime/orderAccess.inline.hpp"
50 #include "runtime/osThread.hpp"
51 #include "runtime/safepoint.hpp"
52 #include "runtime/signature.hpp"
53 #include "runtime/stubCodeGenerator.hpp"
54 #include "runtime/stubRoutines.hpp"
55 #include "runtime/sweeper.hpp"
56 #include "runtime/synchronizer.hpp"
57 #include "runtime/thread.inline.hpp"
58 #include "runtime/timerTrace.hpp"
59 #include "services/runtimeService.hpp"
60 #include "trace/tracing.hpp"
61 #include "trace/traceMacros.hpp"
62 #include "utilities/events.hpp"
63 #include "utilities/macros.hpp"
64 #if INCLUDE_ALL_GCS
65 #include "gc/cms/concurrentMarkSweepThread.hpp"
66 #include "gc/g1/suspendibleThreadSet.hpp"
67 #endif // INCLUDE_ALL_GCS
68 #ifdef COMPILER1
69 #include "c1/c1_globals.hpp"
70 #endif
71
72 // --------------------------------------------------------------------------------------------------
73 // Implementation of Safepoint begin/end
74
75 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
76 volatile int SafepointSynchronize::_waiting_to_block = 0;
77 volatile int SafepointSynchronize::_safepoint_counter = 0;
78 int SafepointSynchronize::_current_jni_active_count = 0;
79 long SafepointSynchronize::_end_of_last_safepoint = 0;
80 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
81 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
82 static bool timeout_error_printed = false;
83
84 // Roll all threads forward to a safepoint and suspend them all
85 void SafepointSynchronize::begin() {
86 EventSafepointBegin begin_event;
87 Thread* myThread = Thread::current();
88 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
89
90 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
91 _safepoint_begin_time = os::javaTimeNanos();
92 _ts_of_current_safepoint = tty->time_stamp().seconds();
93 }
94
95 #if INCLUDE_ALL_GCS
96 if (UseConcMarkSweepGC) {
97 // In the future we should investigate whether CMS can use the
98 // more-general mechanism below. DLD (01/05).
99 ConcurrentMarkSweepThread::synchronize(false);
100 } else if (UseG1GC) {
101 SuspendibleThreadSet::synchronize();
102 }
103 #endif // INCLUDE_ALL_GCS
104
105 // By getting the Threads_lock, we assure that no threads are about to start or
106 // exit. It is released again in SafepointSynchronize::end().
107 Threads_lock->lock();
108
109 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
110
111 int nof_threads = Threads::number_of_threads();
112
113 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads);
114
115 RuntimeService::record_safepoint_begin();
116
117 MutexLocker mu(Safepoint_lock);
118
119 // Reset the count of active JNI critical threads
120 _current_jni_active_count = 0;
121
122 // Set number of threads to wait for, before we initiate the callbacks
123 _waiting_to_block = nof_threads;
124 TryingToBlock = 0 ;
125 int still_running = nof_threads;
126
127 // Save the starting time, so that it can be compared to see if this has taken
128 // too long to complete.
129 jlong safepoint_limit_time = 0;
130 timeout_error_printed = false;
131
132 // PrintSafepointStatisticsTimeout can be specified separately. When
133 // specified, PrintSafepointStatistics will be set to true in
134 // deferred_initialize_stat method. The initialization has to be done
135 // early enough to avoid any races. See bug 6880029 for details.
136 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
137 deferred_initialize_stat();
138 }
139
140 // Begin the process of bringing the system to a safepoint.
141 // Java threads can be in several different states and are
142 // stopped by different mechanisms:
143 //
144 // 1. Running interpreted
145 // The interpreter dispatch table is changed to force it to
146 // check for a safepoint condition between bytecodes.
147 // 2. Running in native code
148 // When returning from the native code, a Java thread must check
149 // the safepoint _state to see if we must block. If the
150 // VM thread sees a Java thread in native, it does
151 // not wait for this thread to block. The order of the memory
152 // writes and reads of both the safepoint state and the Java
153 // threads state is critical. In order to guarantee that the
154 // memory writes are serialized with respect to each other,
155 // the VM thread issues a memory barrier instruction
156 // (on MP systems). In order to avoid the overhead of issuing
157 // a memory barrier for each Java thread making native calls, each Java
158 // thread performs a write to a single memory page after changing
159 // the thread state. The VM thread performs a sequence of
160 // mprotect OS calls which forces all previous writes from all
161 // Java threads to be serialized. This is done in the
162 // os::serialize_thread_states() call. This has proven to be
163 // much more efficient than executing a membar instruction
164 // on every call to native code.
165 // 3. Running compiled Code
166 // Compiled code reads a global (Safepoint Polling) page that
167 // is set to fault if we are trying to get to a safepoint.
168 // 4. Blocked
169 // A thread which is blocked will not be allowed to return from the
170 // block condition until the safepoint operation is complete.
171 // 5. In VM or Transitioning between states
172 // If a Java thread is currently running in the VM or transitioning
173 // between states, the safepointing code will wait for the thread to
174 // block itself when it attempts transitions to a new state.
175 //
176 {
177 EventSafepointStateSynchronization sync_event;
178 int initial_running = 0;
179
180 _state = _synchronizing;
181 OrderAccess::fence();
182
183 // Flush all thread states to memory
184 if (!UseMembar) {
185 os::serialize_thread_states();
186 }
187
188 // Make interpreter safepoint aware
189 Interpreter::notice_safepoints();
190
191 if (DeferPollingPageLoopCount < 0) {
192 // Make polling safepoint aware
193 guarantee (PageArmed == 0, "invariant") ;
194 PageArmed = 1 ;
195 os::make_polling_page_unreadable();
196 }
197
198 // Consider using active_processor_count() ... but that call is expensive.
199 int ncpus = os::processor_count() ;
200
201 #ifdef ASSERT
202 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
203 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
204 // Clear the visited flag to ensure that the critical counts are collected properly.
205 cur->set_visited_for_critical_count(false);
206 }
207 #endif // ASSERT
208
209 if (SafepointTimeout)
210 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
211
212 // Iterate through all threads until it have been determined how to stop them all at a safepoint
213 unsigned int iterations = 0;
214 int steps = 0 ;
215 while(still_running > 0) {
216 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
217 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
218 ThreadSafepointState *cur_state = cur->safepoint_state();
219 if (cur_state->is_running()) {
220 cur_state->examine_state_of_thread();
221 if (!cur_state->is_running()) {
222 still_running--;
223 // consider adjusting steps downward:
224 // steps = 0
225 // steps -= NNN
226 // steps >>= 1
227 // steps = MIN(steps, 2000-100)
228 // if (iterations != 0) steps -= NNN
229 }
230 LogTarget(Trace, safepoint) lt;
231 if (lt.is_enabled()) {
232 ResourceMark rm;
233 LogStream ls(lt);
234 cur_state->print_on(&ls);
235 }
236 }
237 }
238
239 if (iterations == 0) {
240 initial_running = still_running;
241 if (PrintSafepointStatistics) {
242 begin_statistics(nof_threads, still_running);
243 }
244 }
245
246 if (still_running > 0) {
247 // Check for if it takes to long
248 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
249 print_safepoint_timeout(_spinning_timeout);
250 }
251
252 // Spin to avoid context switching.
253 // There's a tension between allowing the mutators to run (and rendezvous)
254 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
255 // a mutator might otherwise use profitably to reach a safepoint. Excessive
256 // spinning by the VM thread on a saturated system can increase rendezvous latency.
257 // Blocking or yielding incur their own penalties in the form of context switching
258 // and the resultant loss of $ residency.
259 //
260 // Further complicating matters is that yield() does not work as naively expected
261 // on many platforms -- yield() does not guarantee that any other ready threads
262 // will run. As such we revert to naked_short_sleep() after some number of iterations.
263 // nakes_short_sleep() is implemented as a short unconditional sleep.
264 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
265 // can actually increase the time it takes the VM thread to detect that a system-wide
266 // stop-the-world safepoint has been reached. In a pathological scenario such as that
267 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
268 // In that case the mutators will be stalled waiting for the safepoint to complete and the
269 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
270 // will eventually wake up and detect that all mutators are safe, at which point
271 // we'll again make progress.
272 //
273 // Beware too that that the VMThread typically runs at elevated priority.
274 // Its default priority is higher than the default mutator priority.
275 // Obviously, this complicates spinning.
276 //
277 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
278 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
279 //
280 // See the comments in synchronizer.cpp for additional remarks on spinning.
281 //
282 // In the future we might:
283 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
284 // This is tricky as the path used by a thread exiting the JVM (say on
285 // on JNI call-out) simply stores into its state field. The burden
286 // is placed on the VM thread, which must poll (spin).
287 // 2. Find something useful to do while spinning. If the safepoint is GC-related
288 // we might aggressively scan the stacks of threads that are already safe.
289 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
290 // If all the mutators are ONPROC there's no reason to sleep or yield.
291 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
292 // 5. Check system saturation. If the system is not fully saturated then
293 // simply spin and avoid sleep/yield.
294 // 6. As still-running mutators rendezvous they could unpark the sleeping
295 // VMthread. This works well for still-running mutators that become
296 // safe. The VMthread must still poll for mutators that call-out.
297 // 7. Drive the policy on time-since-begin instead of iterations.
298 // 8. Consider making the spin duration a function of the # of CPUs:
299 // Spin = (((ncpus-1) * M) + K) + F(still_running)
300 // Alternately, instead of counting iterations of the outer loop
301 // we could count the # of threads visited in the inner loop, above.
302 // 9. On windows consider using the return value from SwitchThreadTo()
303 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
304
305 if (int(iterations) == DeferPollingPageLoopCount) {
306 guarantee (PageArmed == 0, "invariant") ;
307 PageArmed = 1 ;
308 os::make_polling_page_unreadable();
309 }
310
311 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
312 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
313 ++steps ;
314 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
315 SpinPause() ; // MP-Polite spin
316 } else
317 if (steps < DeferThrSuspendLoopCount) {
318 os::naked_yield() ;
319 } else {
320 os::naked_short_sleep(1);
321 }
322
323 iterations ++ ;
324 }
325 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
326 }
327 assert(still_running == 0, "sanity check");
328
329 if (PrintSafepointStatistics) {
330 update_statistics_on_spin_end();
331 }
332
333 if (sync_event.should_commit()) {
334 sync_event.set_safepointId(safepoint_counter());
335 sync_event.set_initialThreadCount(initial_running);
336 sync_event.set_runningThreadCount(_waiting_to_block);
337 sync_event.set_iterations(iterations);
338 sync_event.commit();
339 }
340 } //EventSafepointStateSync
341
342 // wait until all threads are stopped
343 {
344 EventSafepointWaitBlocked wait_blocked_event;
345 int initial_waiting_to_block = _waiting_to_block;
346
347 while (_waiting_to_block > 0) {
348 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
349 if (!SafepointTimeout || timeout_error_printed) {
350 Safepoint_lock->wait(true); // true, means with no safepoint checks
351 } else {
352 // Compute remaining time
353 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
354
355 // If there is no remaining time, then there is an error
356 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
357 print_safepoint_timeout(_blocking_timeout);
358 }
359 }
360 }
361 assert(_waiting_to_block == 0, "sanity check");
362
363 #ifndef PRODUCT
364 if (SafepointTimeout) {
365 jlong current_time = os::javaTimeNanos();
366 if (safepoint_limit_time < current_time) {
367 tty->print_cr("# SafepointSynchronize: Finished after "
368 INT64_FORMAT_W(6) " ms",
369 ((current_time - safepoint_limit_time) / MICROUNITS +
370 (jlong)SafepointTimeoutDelay));
371 }
372 }
373 #endif
374
375 assert((_safepoint_counter & 0x1) == 0, "must be even");
376 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
377 _safepoint_counter ++;
378
379 // Record state
380 _state = _synchronized;
381
382 OrderAccess::fence();
383
384 if (wait_blocked_event.should_commit()) {
385 wait_blocked_event.set_safepointId(safepoint_counter());
386 wait_blocked_event.set_runningThreadCount(initial_waiting_to_block);
387 wait_blocked_event.commit();
388 }
389 } // EventSafepointWaitBlocked
390
391 #ifdef ASSERT
392 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
393 // make sure all the threads were visited
394 assert(cur->was_visited_for_critical_count(), "missed a thread");
395 }
396 #endif // ASSERT
397
398 // Update the count of active JNI critical regions
399 GCLocker::set_jni_lock_count(_current_jni_active_count);
400
401 if (log_is_enabled(Debug, safepoint)) {
402 log_debug(safepoint)("Entering safepoint region: %s", VMThread::vm_safepoint_description());
403 }
404
405 RuntimeService::record_safepoint_synchronized();
406 if (PrintSafepointStatistics) {
407 update_statistics_on_sync_end(os::javaTimeNanos());
408 }
409
410 // Call stuff that needs to be run when a safepoint is just about to be completed
411 {
412 EventSafepointCleanup cleanup_event;
413 do_cleanup_tasks();
414 if (cleanup_event.should_commit()) {
415 cleanup_event.set_safepointId(safepoint_counter());
416 cleanup_event.commit();
417 }
418 }
419
420 if (PrintSafepointStatistics) {
421 // Record how much time spend on the above cleanup tasks
422 update_statistics_on_cleanup_end(os::javaTimeNanos());
423 }
424 if (begin_event.should_commit()) {
425 begin_event.set_safepointId(safepoint_counter());
426 begin_event.set_totalThreadCount(nof_threads);
427 begin_event.set_jniCriticalThreadCount(_current_jni_active_count);
428 begin_event.commit();
429 }
430 }
431
432 // Wake up all threads, so they are ready to resume execution after the safepoint
433 // operation has been carried out
434 void SafepointSynchronize::end() {
435 EventSafepointEnd event;
436 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id"
437
438 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
439 assert((_safepoint_counter & 0x1) == 1, "must be odd");
440 _safepoint_counter ++;
441 // memory fence isn't required here since an odd _safepoint_counter
442 // value can do no harm and a fence is issued below anyway.
443
444 DEBUG_ONLY(Thread* myThread = Thread::current();)
445 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
446
447 if (PrintSafepointStatistics) {
448 end_statistics(os::javaTimeNanos());
449 }
450
451 #ifdef ASSERT
452 // A pending_exception cannot be installed during a safepoint. The threads
453 // may install an async exception after they come back from a safepoint into
454 // pending_exception after they unblock. But that should happen later.
455 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
456 assert (!(cur->has_pending_exception() &&
457 cur->safepoint_state()->is_at_poll_safepoint()),
458 "safepoint installed a pending exception");
459 }
460 #endif // ASSERT
461
462 if (PageArmed) {
463 // Make polling safepoint aware
464 os::make_polling_page_readable();
465 PageArmed = 0 ;
466 }
467
468 // Remove safepoint check from interpreter
469 Interpreter::ignore_safepoints();
470
471 {
472 MutexLocker mu(Safepoint_lock);
473
474 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
475
476 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
477 // when they get restarted.
478 _state = _not_synchronized;
479 OrderAccess::fence();
480
481 log_debug(safepoint)("Leaving safepoint region");
482
483 // Start suspended threads
484 for(JavaThread *current = Threads::first(); current; current = current->next()) {
485 // A problem occurring on Solaris is when attempting to restart threads
486 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
487 // to the next one (since it has been running the longest). We then have
488 // to wait for a cpu to become available before we can continue restarting
489 // threads.
490 // FIXME: This causes the performance of the VM to degrade when active and with
491 // large numbers of threads. Apparently this is due to the synchronous nature
492 // of suspending threads.
493 //
494 // TODO-FIXME: the comments above are vestigial and no longer apply.
495 // Furthermore, using solaris' schedctl in this particular context confers no benefit
496 if (VMThreadHintNoPreempt) {
497 os::hint_no_preempt();
498 }
499 ThreadSafepointState* cur_state = current->safepoint_state();
500 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
501 cur_state->restart();
502 assert(cur_state->is_running(), "safepoint state has not been reset");
503 }
504
505 RuntimeService::record_safepoint_end();
506
507 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
508 // blocked in signal_thread_blocked
509 Threads_lock->unlock();
510
511 }
512 #if INCLUDE_ALL_GCS
513 // If there are any concurrent GC threads resume them.
514 if (UseConcMarkSweepGC) {
515 ConcurrentMarkSweepThread::desynchronize(false);
516 } else if (UseG1GC) {
517 SuspendibleThreadSet::desynchronize();
518 }
519 #endif // INCLUDE_ALL_GCS
520 // record this time so VMThread can keep track how much time has elapsed
521 // since last safepoint.
522 _end_of_last_safepoint = os::javaTimeMillis();
523
524 if (event.should_commit()) {
525 event.set_safepointId(safepoint_id);
526 event.commit();
527 }
528 }
529
530 bool SafepointSynchronize::is_cleanup_needed() {
531 // Need a safepoint if there are many monitors to deflate.
532 if (ObjectSynchronizer::is_cleanup_needed()) return true;
533 // Need a safepoint if some inline cache buffers is non-empty
534 if (!InlineCacheBuffer::is_empty()) return true;
535 return false;
536 }
537
538 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) {
539 if (event.should_commit()) {
540 event.set_safepointId(SafepointSynchronize::safepoint_counter());
541 event.set_name(name);
542 event.commit();
543 }
544 }
545
546 // Various cleaning tasks that should be done periodically at safepoints
547 void SafepointSynchronize::do_cleanup_tasks() {
548 {
549 const char* name = "deflating idle monitors";
550 EventSafepointCleanupTask event;
551 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
552 ObjectSynchronizer::deflate_idle_monitors();
553 event_safepoint_cleanup_task_commit(event, name);
554 }
555
556 {
557 const char* name = "updating inline caches";
558 EventSafepointCleanupTask event;
559 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
560 InlineCacheBuffer::update_inline_caches();
561 event_safepoint_cleanup_task_commit(event, name);
562 }
563 {
564 const char* name = "compilation policy safepoint handler";
565 EventSafepointCleanupTask event;
566 TraceTime timer("compilation policy safepoint handler", TRACETIME_LOG(Info, safepoint, cleanup));
567 CompilationPolicy::policy()->do_safepoint_work();
568 event_safepoint_cleanup_task_commit(event, name);
569 }
570
571 {
572 const char* name = "mark nmethods";
573 EventSafepointCleanupTask event;
574 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
575 NMethodSweeper::mark_active_nmethods();
576 event_safepoint_cleanup_task_commit(event, name);
577 }
578
579 if (SymbolTable::needs_rehashing()) {
580 const char* name = "rehashing symbol table";
581 EventSafepointCleanupTask event;
582 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
583 SymbolTable::rehash_table();
584 event_safepoint_cleanup_task_commit(event, name);
585 }
586
587 if (StringTable::needs_rehashing()) {
588 const char* name = "rehashing string table";
589 EventSafepointCleanupTask event;
590 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
591 StringTable::rehash_table();
592 event_safepoint_cleanup_task_commit(event, name);
593 }
594
595 {
596 // CMS delays purging the CLDG until the beginning of the next safepoint and to
597 // make sure concurrent sweep is done
598 const char* name = "purging class loader data graph";
599 EventSafepointCleanupTask event;
600 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
601 ClassLoaderDataGraph::purge_if_needed();
602 event_safepoint_cleanup_task_commit(event, name);
603 }
604 }
605
606
607 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
608 switch(state) {
609 case _thread_in_native:
610 // native threads are safe if they have no java stack or have walkable stack
611 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
612
613 // blocked threads should have already have walkable stack
614 case _thread_blocked:
615 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
616 return true;
617
618 default:
619 return false;
620 }
621 }
622
623
624 // See if the thread is running inside a lazy critical native and
625 // update the thread critical count if so. Also set a suspend flag to
626 // cause the native wrapper to return into the JVM to do the unlock
627 // once the native finishes.
628 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
629 if (state == _thread_in_native &&
630 thread->has_last_Java_frame() &&
631 thread->frame_anchor()->walkable()) {
632 // This thread might be in a critical native nmethod so look at
633 // the top of the stack and increment the critical count if it
634 // is.
635 frame wrapper_frame = thread->last_frame();
636 CodeBlob* stub_cb = wrapper_frame.cb();
637 if (stub_cb != NULL &&
638 stub_cb->is_nmethod() &&
639 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
640 // A thread could potentially be in a critical native across
641 // more than one safepoint, so only update the critical state on
642 // the first one. When it returns it will perform the unlock.
643 if (!thread->do_critical_native_unlock()) {
644 #ifdef ASSERT
645 if (!thread->in_critical()) {
646 GCLocker::increment_debug_jni_lock_count();
647 }
648 #endif
649 thread->enter_critical();
650 // Make sure the native wrapper calls back on return to
651 // perform the needed critical unlock.
652 thread->set_critical_native_unlock();
653 }
654 }
655 }
656 }
657
658
659
660 // -------------------------------------------------------------------------------------------------------
661 // Implementation of Safepoint callback point
662
663 void SafepointSynchronize::block(JavaThread *thread) {
664 assert(thread != NULL, "thread must be set");
665 assert(thread->is_Java_thread(), "not a Java thread");
666
667 // Threads shouldn't block if they are in the middle of printing, but...
668 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
669
670 // Only bail from the block() call if the thread is gone from the
671 // thread list; starting to exit should still block.
672 if (thread->is_terminated()) {
673 // block current thread if we come here from native code when VM is gone
674 thread->block_if_vm_exited();
675
676 // otherwise do nothing
677 return;
678 }
679
680 JavaThreadState state = thread->thread_state();
681 thread->frame_anchor()->make_walkable(thread);
682
683 // Check that we have a valid thread_state at this point
684 switch(state) {
685 case _thread_in_vm_trans:
686 case _thread_in_Java: // From compiled code
687
688 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
689 // we pretend we are still in the VM.
690 thread->set_thread_state(_thread_in_vm);
691
692 if (is_synchronizing()) {
693 Atomic::inc (&TryingToBlock) ;
694 }
695
696 // We will always be holding the Safepoint_lock when we are examine the state
697 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
698 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
699 Safepoint_lock->lock_without_safepoint_check();
700 if (is_synchronizing()) {
701 // Decrement the number of threads to wait for and signal vm thread
702 assert(_waiting_to_block > 0, "sanity check");
703 _waiting_to_block--;
704 thread->safepoint_state()->set_has_called_back(true);
705
706 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
707 if (thread->in_critical()) {
708 // Notice that this thread is in a critical section
709 increment_jni_active_count();
710 }
711
712 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
713 if (_waiting_to_block == 0) {
714 Safepoint_lock->notify_all();
715 }
716 }
717
718 // We transition the thread to state _thread_blocked here, but
719 // we can't do our usual check for external suspension and then
720 // self-suspend after the lock_without_safepoint_check() call
721 // below because we are often called during transitions while
722 // we hold different locks. That would leave us suspended while
723 // holding a resource which results in deadlocks.
724 thread->set_thread_state(_thread_blocked);
725 Safepoint_lock->unlock();
726
727 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
728 // the entire safepoint, the threads will all line up here during the safepoint.
729 Threads_lock->lock_without_safepoint_check();
730 // restore original state. This is important if the thread comes from compiled code, so it
731 // will continue to execute with the _thread_in_Java state.
732 thread->set_thread_state(state);
733 Threads_lock->unlock();
734 break;
735
736 case _thread_in_native_trans:
737 case _thread_blocked_trans:
738 case _thread_new_trans:
739 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
740 thread->print_thread_state();
741 fatal("Deadlock in safepoint code. "
742 "Should have called back to the VM before blocking.");
743 }
744
745 // We transition the thread to state _thread_blocked here, but
746 // we can't do our usual check for external suspension and then
747 // self-suspend after the lock_without_safepoint_check() call
748 // below because we are often called during transitions while
749 // we hold different locks. That would leave us suspended while
750 // holding a resource which results in deadlocks.
751 thread->set_thread_state(_thread_blocked);
752
753 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
754 // the safepoint code might still be waiting for it to block. We need to change the state here,
755 // so it can see that it is at a safepoint.
756
757 // Block until the safepoint operation is completed.
758 Threads_lock->lock_without_safepoint_check();
759
760 // Restore state
761 thread->set_thread_state(state);
762
763 Threads_lock->unlock();
764 break;
765
766 default:
767 fatal("Illegal threadstate encountered: %d", state);
768 }
769
770 // Check for pending. async. exceptions or suspends - except if the
771 // thread was blocked inside the VM. has_special_runtime_exit_condition()
772 // is called last since it grabs a lock and we only want to do that when
773 // we must.
774 //
775 // Note: we never deliver an async exception at a polling point as the
776 // compiler may not have an exception handler for it. The polling
777 // code will notice the async and deoptimize and the exception will
778 // be delivered. (Polling at a return point is ok though). Sure is
779 // a lot of bother for a deprecated feature...
780 //
781 // We don't deliver an async exception if the thread state is
782 // _thread_in_native_trans so JNI functions won't be called with
783 // a surprising pending exception. If the thread state is going back to java,
784 // async exception is checked in check_special_condition_for_native_trans().
785
786 if (state != _thread_blocked_trans &&
787 state != _thread_in_vm_trans &&
788 thread->has_special_runtime_exit_condition()) {
789 thread->handle_special_runtime_exit_condition(
790 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
791 }
792 }
793
794 // ------------------------------------------------------------------------------------------------------
795 // Exception handlers
796
797
798 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
799 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
800 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
801 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
802
803 if (ShowSafepointMsgs) {
804 tty->print("handle_polling_page_exception: ");
805 }
806
807 if (PrintSafepointStatistics) {
808 inc_page_trap_count();
809 }
810
811 ThreadSafepointState* state = thread->safepoint_state();
812
813 state->handle_polling_page_exception();
814 }
815
816
817 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
818 if (!timeout_error_printed) {
819 timeout_error_printed = true;
820 // Print out the thread info which didn't reach the safepoint for debugging
821 // purposes (useful when there are lots of threads in the debugger).
822 tty->cr();
823 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
824 if (reason == _spinning_timeout) {
825 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
826 } else if (reason == _blocking_timeout) {
827 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
828 }
829
830 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
831 ThreadSafepointState *cur_state;
832 ResourceMark rm;
833 for(JavaThread *cur_thread = Threads::first(); cur_thread;
834 cur_thread = cur_thread->next()) {
835 cur_state = cur_thread->safepoint_state();
836
837 if (cur_thread->thread_state() != _thread_blocked &&
838 ((reason == _spinning_timeout && cur_state->is_running()) ||
839 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
840 tty->print("# ");
841 cur_thread->print();
842 tty->cr();
843 }
844 }
845 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
846 }
847
848 // To debug the long safepoint, specify both DieOnSafepointTimeout &
849 // ShowMessageBoxOnError.
850 if (DieOnSafepointTimeout) {
851 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
852 SafepointTimeoutDelay, VMThread::vm_safepoint_description());
853 }
854 }
855
856
857 // -------------------------------------------------------------------------------------------------------
858 // Implementation of ThreadSafepointState
859
860 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
861 _thread = thread;
862 _type = _running;
863 _has_called_back = false;
864 _at_poll_safepoint = false;
865 }
866
867 void ThreadSafepointState::create(JavaThread *thread) {
868 ThreadSafepointState *state = new ThreadSafepointState(thread);
869 thread->set_safepoint_state(state);
870 }
871
872 void ThreadSafepointState::destroy(JavaThread *thread) {
873 if (thread->safepoint_state()) {
874 delete(thread->safepoint_state());
875 thread->set_safepoint_state(NULL);
876 }
877 }
878
879 void ThreadSafepointState::examine_state_of_thread() {
880 assert(is_running(), "better be running or just have hit safepoint poll");
881
882 JavaThreadState state = _thread->thread_state();
883
884 // Save the state at the start of safepoint processing.
885 _orig_thread_state = state;
886
887 // Check for a thread that is suspended. Note that thread resume tries
888 // to grab the Threads_lock which we own here, so a thread cannot be
889 // resumed during safepoint synchronization.
890
891 // We check to see if this thread is suspended without locking to
892 // avoid deadlocking with a third thread that is waiting for this
893 // thread to be suspended. The third thread can notice the safepoint
894 // that we're trying to start at the beginning of its SR_lock->wait()
895 // call. If that happens, then the third thread will block on the
896 // safepoint while still holding the underlying SR_lock. We won't be
897 // able to get the SR_lock and we'll deadlock.
898 //
899 // We don't need to grab the SR_lock here for two reasons:
900 // 1) The suspend flags are both volatile and are set with an
901 // Atomic::cmpxchg() call so we should see the suspended
902 // state right away.
903 // 2) We're being called from the safepoint polling loop; if
904 // we don't see the suspended state on this iteration, then
905 // we'll come around again.
906 //
907 bool is_suspended = _thread->is_ext_suspended();
908 if (is_suspended) {
909 roll_forward(_at_safepoint);
910 return;
911 }
912
913 // Some JavaThread states have an initial safepoint state of
914 // running, but are actually at a safepoint. We will happily
915 // agree and update the safepoint state here.
916 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
917 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
918 roll_forward(_at_safepoint);
919 return;
920 }
921
922 if (state == _thread_in_vm) {
923 roll_forward(_call_back);
924 return;
925 }
926
927 // All other thread states will continue to run until they
928 // transition and self-block in state _blocked
929 // Safepoint polling in compiled code causes the Java threads to do the same.
930 // Note: new threads may require a malloc so they must be allowed to finish
931
932 assert(is_running(), "examine_state_of_thread on non-running thread");
933 return;
934 }
935
936 // Returns true is thread could not be rolled forward at present position.
937 void ThreadSafepointState::roll_forward(suspend_type type) {
938 _type = type;
939
940 switch(_type) {
941 case _at_safepoint:
942 SafepointSynchronize::signal_thread_at_safepoint();
943 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
944 if (_thread->in_critical()) {
945 // Notice that this thread is in a critical section
946 SafepointSynchronize::increment_jni_active_count();
947 }
948 break;
949
950 case _call_back:
951 set_has_called_back(false);
952 break;
953
954 case _running:
955 default:
956 ShouldNotReachHere();
957 }
958 }
959
960 void ThreadSafepointState::restart() {
961 switch(type()) {
962 case _at_safepoint:
963 case _call_back:
964 break;
965
966 case _running:
967 default:
968 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
969 p2i(_thread), _type);
970 _thread->print();
971 ShouldNotReachHere();
972 }
973 _type = _running;
974 set_has_called_back(false);
975 }
976
977
978 void ThreadSafepointState::print_on(outputStream *st) const {
979 const char *s = NULL;
980
981 switch(_type) {
982 case _running : s = "_running"; break;
983 case _at_safepoint : s = "_at_safepoint"; break;
984 case _call_back : s = "_call_back"; break;
985 default:
986 ShouldNotReachHere();
987 }
988
989 st->print_cr("Thread: " INTPTR_FORMAT
990 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
991 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
992 _at_poll_safepoint);
993
994 _thread->print_thread_state_on(st);
995 }
996
997 // ---------------------------------------------------------------------------------------------------------------------
998
999 // Block the thread at the safepoint poll or poll return.
1000 void ThreadSafepointState::handle_polling_page_exception() {
1001
1002 // Check state. block() will set thread state to thread_in_vm which will
1003 // cause the safepoint state _type to become _call_back.
1004 assert(type() == ThreadSafepointState::_running,
1005 "polling page exception on thread not running state");
1006
1007 // Step 1: Find the nmethod from the return address
1008 if (ShowSafepointMsgs && Verbose) {
1009 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
1010 }
1011 address real_return_addr = thread()->saved_exception_pc();
1012
1013 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1014 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1015 CompiledMethod* nm = (CompiledMethod*)cb;
1016
1017 // Find frame of caller
1018 frame stub_fr = thread()->last_frame();
1019 CodeBlob* stub_cb = stub_fr.cb();
1020 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1021 RegisterMap map(thread(), true);
1022 frame caller_fr = stub_fr.sender(&map);
1023
1024 // Should only be poll_return or poll
1025 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1026
1027 // This is a poll immediately before a return. The exception handling code
1028 // has already had the effect of causing the return to occur, so the execution
1029 // will continue immediately after the call. In addition, the oopmap at the
1030 // return point does not mark the return value as an oop (if it is), so
1031 // it needs a handle here to be updated.
1032 if( nm->is_at_poll_return(real_return_addr) ) {
1033 // See if return type is an oop.
1034 bool return_oop = nm->method()->is_returning_oop();
1035 Handle return_value;
1036 if (return_oop) {
1037 // The oop result has been saved on the stack together with all
1038 // the other registers. In order to preserve it over GCs we need
1039 // to keep it in a handle.
1040 oop result = caller_fr.saved_oop_result(&map);
1041 assert(result == NULL || result->is_oop(), "must be oop");
1042 return_value = Handle(thread(), result);
1043 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1044 }
1045
1046 // Block the thread
1047 SafepointSynchronize::block(thread());
1048
1049 // restore oop result, if any
1050 if (return_oop) {
1051 caller_fr.set_saved_oop_result(&map, return_value());
1052 }
1053 }
1054
1055 // This is a safepoint poll. Verify the return address and block.
1056 else {
1057 set_at_poll_safepoint(true);
1058
1059 // verify the blob built the "return address" correctly
1060 assert(real_return_addr == caller_fr.pc(), "must match");
1061
1062 // Block the thread
1063 SafepointSynchronize::block(thread());
1064 set_at_poll_safepoint(false);
1065
1066 // If we have a pending async exception deoptimize the frame
1067 // as otherwise we may never deliver it.
1068 if (thread()->has_async_condition()) {
1069 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1070 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1071 }
1072
1073 // If an exception has been installed we must check for a pending deoptimization
1074 // Deoptimize frame if exception has been thrown.
1075
1076 if (thread()->has_pending_exception() ) {
1077 RegisterMap map(thread(), true);
1078 frame caller_fr = stub_fr.sender(&map);
1079 if (caller_fr.is_deoptimized_frame()) {
1080 // The exception patch will destroy registers that are still
1081 // live and will be needed during deoptimization. Defer the
1082 // Async exception should have deferred the exception until the
1083 // next safepoint which will be detected when we get into
1084 // the interpreter so if we have an exception now things
1085 // are messed up.
1086
1087 fatal("Exception installed and deoptimization is pending");
1088 }
1089 }
1090 }
1091 }
1092
1093
1094 //
1095 // Statistics & Instrumentations
1096 //
1097 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1098 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1099 int SafepointSynchronize::_cur_stat_index = 0;
1100 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1101 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1102 jlong SafepointSynchronize::_max_sync_time = 0;
1103 jlong SafepointSynchronize::_max_vmop_time = 0;
1104 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1105
1106 static jlong cleanup_end_time = 0;
1107 static bool need_to_track_page_armed_status = false;
1108 static bool init_done = false;
1109
1110 // Helper method to print the header.
1111 static void print_header() {
1112 // The number of spaces is significant here, and should match the format
1113 // specifiers in print_statistics().
1114
1115 tty->print(" vmop "
1116 "[ threads: total initially_running wait_to_block ]"
1117 "[ time: spin block sync cleanup vmop ] ");
1118
1119 // no page armed status printed out if it is always armed.
1120 if (need_to_track_page_armed_status) {
1121 tty->print("page_armed ");
1122 }
1123
1124 tty->print_cr("page_trap_count");
1125 }
1126
1127 void SafepointSynchronize::deferred_initialize_stat() {
1128 if (init_done) return;
1129
1130 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1131 // be printed right away, in which case, _safepoint_stats will regress to
1132 // a single element array. Otherwise, it is a circular ring buffer with default
1133 // size of PrintSafepointStatisticsCount.
1134 int stats_array_size;
1135 if (PrintSafepointStatisticsTimeout > 0) {
1136 stats_array_size = 1;
1137 PrintSafepointStatistics = true;
1138 } else {
1139 stats_array_size = PrintSafepointStatisticsCount;
1140 }
1141 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1142 * sizeof(SafepointStats), mtInternal);
1143 guarantee(_safepoint_stats != NULL,
1144 "not enough memory for safepoint instrumentation data");
1145
1146 if (DeferPollingPageLoopCount >= 0) {
1147 need_to_track_page_armed_status = true;
1148 }
1149 init_done = true;
1150 }
1151
1152 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1153 assert(init_done, "safepoint statistics array hasn't been initialized");
1154 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1155
1156 spstat->_time_stamp = _ts_of_current_safepoint;
1157
1158 VM_Operation *op = VMThread::vm_operation();
1159 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1160 if (op != NULL) {
1161 _safepoint_reasons[spstat->_vmop_type]++;
1162 }
1163
1164 spstat->_nof_total_threads = nof_threads;
1165 spstat->_nof_initial_running_threads = nof_running;
1166 spstat->_nof_threads_hit_page_trap = 0;
1167
1168 // Records the start time of spinning. The real time spent on spinning
1169 // will be adjusted when spin is done. Same trick is applied for time
1170 // spent on waiting for threads to block.
1171 if (nof_running != 0) {
1172 spstat->_time_to_spin = os::javaTimeNanos();
1173 } else {
1174 spstat->_time_to_spin = 0;
1175 }
1176 }
1177
1178 void SafepointSynchronize::update_statistics_on_spin_end() {
1179 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1180
1181 jlong cur_time = os::javaTimeNanos();
1182
1183 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1184 if (spstat->_nof_initial_running_threads != 0) {
1185 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1186 }
1187
1188 if (need_to_track_page_armed_status) {
1189 spstat->_page_armed = (PageArmed == 1);
1190 }
1191
1192 // Records the start time of waiting for to block. Updated when block is done.
1193 if (_waiting_to_block != 0) {
1194 spstat->_time_to_wait_to_block = cur_time;
1195 } else {
1196 spstat->_time_to_wait_to_block = 0;
1197 }
1198 }
1199
1200 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1201 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1202
1203 if (spstat->_nof_threads_wait_to_block != 0) {
1204 spstat->_time_to_wait_to_block = end_time -
1205 spstat->_time_to_wait_to_block;
1206 }
1207
1208 // Records the end time of sync which will be used to calculate the total
1209 // vm operation time. Again, the real time spending in syncing will be deducted
1210 // from the start of the sync time later when end_statistics is called.
1211 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1212 if (spstat->_time_to_sync > _max_sync_time) {
1213 _max_sync_time = spstat->_time_to_sync;
1214 }
1215
1216 spstat->_time_to_do_cleanups = end_time;
1217 }
1218
1219 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1220 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1221
1222 // Record how long spent in cleanup tasks.
1223 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1224
1225 cleanup_end_time = end_time;
1226 }
1227
1228 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1229 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1230
1231 // Update the vm operation time.
1232 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1233 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1234 _max_vmop_time = spstat->_time_to_exec_vmop;
1235 }
1236 // Only the sync time longer than the specified
1237 // PrintSafepointStatisticsTimeout will be printed out right away.
1238 // By default, it is -1 meaning all samples will be put into the list.
1239 if ( PrintSafepointStatisticsTimeout > 0) {
1240 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1241 print_statistics();
1242 }
1243 } else {
1244 // The safepoint statistics will be printed out when the _safepoin_stats
1245 // array fills up.
1246 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1247 print_statistics();
1248 _cur_stat_index = 0;
1249 } else {
1250 _cur_stat_index++;
1251 }
1252 }
1253 }
1254
1255 void SafepointSynchronize::print_statistics() {
1256 for (int index = 0; index <= _cur_stat_index; index++) {
1257 if (index % 30 == 0) {
1258 print_header();
1259 }
1260 SafepointStats* sstats = &_safepoint_stats[index];
1261 tty->print("%8.3f: ", sstats->_time_stamp);
1262 tty->print("%-30s [ "
1263 INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " "
1264 "]",
1265 (sstats->_vmop_type == -1 ? "no vm operation" : VM_Operation::name(sstats->_vmop_type)),
1266 sstats->_nof_total_threads,
1267 sstats->_nof_initial_running_threads,
1268 sstats->_nof_threads_wait_to_block);
1269 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1270 tty->print("[ "
1271 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1272 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1273 INT64_FORMAT_W(7) " ] ",
1274 sstats->_time_to_spin / MICROUNITS,
1275 sstats->_time_to_wait_to_block / MICROUNITS,
1276 sstats->_time_to_sync / MICROUNITS,
1277 sstats->_time_to_do_cleanups / MICROUNITS,
1278 sstats->_time_to_exec_vmop / MICROUNITS);
1279
1280 if (need_to_track_page_armed_status) {
1281 tty->print(INT32_FORMAT_W(10) " ", sstats->_page_armed);
1282 }
1283 tty->print_cr(INT32_FORMAT_W(15) " ", sstats->_nof_threads_hit_page_trap);
1284 }
1285 }
1286
1287 // This method will be called when VM exits. It will first call
1288 // print_statistics to print out the rest of the sampling. Then
1289 // it tries to summarize the sampling.
1290 void SafepointSynchronize::print_stat_on_exit() {
1291 if (_safepoint_stats == NULL) return;
1292
1293 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1294
1295 // During VM exit, end_statistics may not get called and in that
1296 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1297 // don't print it out.
1298 // Approximate the vm op time.
1299 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1300 os::javaTimeNanos() - cleanup_end_time;
1301
1302 if ( PrintSafepointStatisticsTimeout < 0 ||
1303 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1304 print_statistics();
1305 }
1306 tty->cr();
1307
1308 // Print out polling page sampling status.
1309 if (!need_to_track_page_armed_status) {
1310 tty->print_cr("Polling page always armed");
1311 } else {
1312 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
1313 DeferPollingPageLoopCount);
1314 }
1315
1316 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1317 if (_safepoint_reasons[index] != 0) {
1318 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1319 _safepoint_reasons[index]);
1320 }
1321 }
1322
1323 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1324 _coalesced_vmop_count);
1325 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1326 _max_sync_time / MICROUNITS);
1327 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1328 INT64_FORMAT_W(5) " ms",
1329 _max_vmop_time / MICROUNITS);
1330 }
1331
1332 // ------------------------------------------------------------------------------------------------
1333 // Non-product code
1334
1335 #ifndef PRODUCT
1336
1337 void SafepointSynchronize::print_state() {
1338 if (_state == _not_synchronized) {
1339 tty->print_cr("not synchronized");
1340 } else if (_state == _synchronizing || _state == _synchronized) {
1341 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1342 "synchronized");
1343
1344 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1345 cur->safepoint_state()->print();
1346 }
1347 }
1348 }
1349
1350 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1351 if (ShowSafepointMsgs) {
1352 va_list ap;
1353 va_start(ap, format);
1354 tty->vprint_cr(format, ap);
1355 va_end(ap);
1356 }
1357 }
1358
1359 #endif // !PRODUCT