1 /*
2 * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/stringTable.hpp"
27 #include "classfile/symbolTable.hpp"
28 #include "classfile/systemDictionary.hpp"
29 #include "code/codeCache.hpp"
30 #include "code/icBuffer.hpp"
31 #include "code/nmethod.hpp"
32 #include "code/pcDesc.hpp"
33 #include "code/scopeDesc.hpp"
34 #include "gc/shared/collectedHeap.hpp"
35 #include "gc/shared/gcLocker.inline.hpp"
36 #include "interpreter/interpreter.hpp"
37 #include "logging/log.hpp"
38 #include "memory/resourceArea.hpp"
39 #include "memory/universe.inline.hpp"
40 #include "oops/oop.inline.hpp"
41 #include "oops/symbol.hpp"
42 #include "runtime/atomic.hpp"
43 #include "runtime/compilationPolicy.hpp"
44 #include "runtime/deoptimization.hpp"
45 #include "runtime/frame.inline.hpp"
46 #include "runtime/interfaceSupport.hpp"
47 #include "runtime/mutexLocker.hpp"
48 #include "runtime/orderAccess.inline.hpp"
49 #include "runtime/osThread.hpp"
50 #include "runtime/safepoint.hpp"
51 #include "runtime/signature.hpp"
52 #include "runtime/stubCodeGenerator.hpp"
53 #include "runtime/stubRoutines.hpp"
54 #include "runtime/sweeper.hpp"
55 #include "runtime/synchronizer.hpp"
56 #include "runtime/thread.inline.hpp"
57 #include "runtime/timerTrace.hpp"
58 #include "services/runtimeService.hpp"
59 #include "utilities/events.hpp"
60 #include "utilities/macros.hpp"
61 #if INCLUDE_ALL_GCS
62 #include "gc/cms/concurrentMarkSweepThread.hpp"
63 #include "gc/g1/suspendibleThreadSet.hpp"
64 #endif // INCLUDE_ALL_GCS
65 #ifdef COMPILER1
66 #include "c1/c1_globals.hpp"
67 #endif
68 #if INCLUDE_TRACE
69 #include "trace/tracing.hpp"
70
71 static void post_safepoint_begin_event(EventSafepointBegin* event,
72 int safepoint_id,
73 int thread_count,
74 int critical_thread_count) {
75 assert(event != NULL, "invariant");
76 if (event->should_commit()) {
77 event->set_safepointId(safepoint_id);
78 event->set_totalThreadCount(thread_count);
79 event->set_jniCriticalThreadCount(critical_thread_count);
80 event->commit();
81 }
82 }
83
84 static void post_safepoint_cleanup_event(EventSafepointCleanup* event,
85 int safepoint_id) {
86 assert(event != NULL, "invariant");
87 if (event->should_commit()) {
88 event->set_safepointId(safepoint_id);
89 event->commit();
90 }
91 }
92
93 static void post_safepoint_synchronize_event(EventSafepointStateSynchronization* event,
94 int safepoint_id,
95 int initial_number_of_threads,
96 int threads_waiting_to_block,
97 unsigned int iterations) {
98 assert(event != NULL, "invariant");
99 if (event->should_commit()) {
100 event->set_safepointId(safepoint_id);
101 event->set_initialThreadCount(initial_number_of_threads);
102 event->set_runningThreadCount(threads_waiting_to_block);
103 event->set_iterations(iterations);
104 event->commit();
105 }
106 }
107
108 static void post_safepoint_wait_blocked_event(EventSafepointWaitBlocked* event,
109 int safepoint_id,
110 int initial_threads_waiting_to_block) {
111 assert(event != NULL, "invariant");
112 if (event->should_commit()) {
113 event->set_safepointId(safepoint_id);
114 event->set_runningThreadCount(initial_threads_waiting_to_block);
115 event->commit();
116 }
117 }
118
119 static void post_safepoint_end_event(EventSafepointEnd* event, int safepoint_id) {
120 assert(event != NULL, "invariant");
121 if (event->should_commit()) {
122 event->set_safepointId(safepoint_id);
123 event->commit();
124 }
125 }
126
127 static void post_safepoint_cleanup_task_event(EventSafepointCleanupTask* event,
128 int safepoint_id,
129 const char* name) {
130 assert(event != NULL, "invariant");
131 if (event->should_commit()) {
132 event->set_safepointId(safepoint_id);
133 event->set_name(name);
134 event->commit();
135 }
136 }
137 #endif // INCLUDE_TRACE
138
139 // --------------------------------------------------------------------------------------------------
140 // Implementation of Safepoint begin/end
141
142 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
143 volatile int SafepointSynchronize::_waiting_to_block = 0;
144 volatile int SafepointSynchronize::_safepoint_counter = 0;
145 int SafepointSynchronize::_current_jni_active_count = 0;
146 long SafepointSynchronize::_end_of_last_safepoint = 0;
147 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
148 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
149 static bool timeout_error_printed = false;
150
151 // Roll all threads forward to a safepoint and suspend them all
152 void SafepointSynchronize::begin() {
153 TRACE_ONLY(EventSafepointBegin begin_event;)
154 Thread* myThread = Thread::current();
155 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
156
157 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
158 _safepoint_begin_time = os::javaTimeNanos();
159 _ts_of_current_safepoint = tty->time_stamp().seconds();
160 }
161
162 #if INCLUDE_ALL_GCS
163 if (UseConcMarkSweepGC) {
164 // In the future we should investigate whether CMS can use the
165 // more-general mechanism below. DLD (01/05).
166 ConcurrentMarkSweepThread::synchronize(false);
167 } else if (UseG1GC) {
168 SuspendibleThreadSet::synchronize();
169 }
170 #endif // INCLUDE_ALL_GCS
171
172 // By getting the Threads_lock, we assure that no threads are about to start or
173 // exit. It is released again in SafepointSynchronize::end().
174 Threads_lock->lock();
175
176 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
177
178 int nof_threads = Threads::number_of_threads();
179
180 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads);
181
182 RuntimeService::record_safepoint_begin();
183
184 MutexLocker mu(Safepoint_lock);
185
186 // Reset the count of active JNI critical threads
187 _current_jni_active_count = 0;
188
189 // Set number of threads to wait for, before we initiate the callbacks
190 _waiting_to_block = nof_threads;
191 TryingToBlock = 0 ;
192 int still_running = nof_threads;
193
194 // Save the starting time, so that it can be compared to see if this has taken
195 // too long to complete.
196 jlong safepoint_limit_time = 0;
197 timeout_error_printed = false;
198
199 // PrintSafepointStatisticsTimeout can be specified separately. When
200 // specified, PrintSafepointStatistics will be set to true in
201 // deferred_initialize_stat method. The initialization has to be done
202 // early enough to avoid any races. See bug 6880029 for details.
203 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
204 deferred_initialize_stat();
205 }
206
207 // Begin the process of bringing the system to a safepoint.
208 // Java threads can be in several different states and are
209 // stopped by different mechanisms:
210 //
211 // 1. Running interpreted
212 // The interpreter dispatch table is changed to force it to
213 // check for a safepoint condition between bytecodes.
214 // 2. Running in native code
215 // When returning from the native code, a Java thread must check
216 // the safepoint _state to see if we must block. If the
217 // VM thread sees a Java thread in native, it does
218 // not wait for this thread to block. The order of the memory
219 // writes and reads of both the safepoint state and the Java
220 // threads state is critical. In order to guarantee that the
221 // memory writes are serialized with respect to each other,
222 // the VM thread issues a memory barrier instruction
223 // (on MP systems). In order to avoid the overhead of issuing
224 // a memory barrier for each Java thread making native calls, each Java
225 // thread performs a write to a single memory page after changing
226 // the thread state. The VM thread performs a sequence of
227 // mprotect OS calls which forces all previous writes from all
228 // Java threads to be serialized. This is done in the
229 // os::serialize_thread_states() call. This has proven to be
230 // much more efficient than executing a membar instruction
231 // on every call to native code.
232 // 3. Running compiled Code
233 // Compiled code reads a global (Safepoint Polling) page that
234 // is set to fault if we are trying to get to a safepoint.
235 // 4. Blocked
236 // A thread which is blocked will not be allowed to return from the
237 // block condition until the safepoint operation is complete.
238 // 5. In VM or Transitioning between states
239 // If a Java thread is currently running in the VM or transitioning
240 // between states, the safepointing code will wait for the thread to
241 // block itself when it attempts transitions to a new state.
242 //
243 {
244 TRACE_ONLY(EventSafepointStateSynchronization sync_event;)
245 int initial_running = 0;
246
247 _state = _synchronizing;
248 OrderAccess::fence();
249
250 // Flush all thread states to memory
251 if (!UseMembar) {
252 os::serialize_thread_states();
253 }
254
255 // Make interpreter safepoint aware
256 Interpreter::notice_safepoints();
257
258 if (DeferPollingPageLoopCount < 0) {
259 // Make polling safepoint aware
260 guarantee (PageArmed == 0, "invariant") ;
261 PageArmed = 1 ;
262 os::make_polling_page_unreadable();
263 }
264
265 // Consider using active_processor_count() ... but that call is expensive.
266 int ncpus = os::processor_count() ;
267
268 #ifdef ASSERT
269 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
270 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
271 // Clear the visited flag to ensure that the critical counts are collected properly.
272 cur->set_visited_for_critical_count(false);
273 }
274 #endif // ASSERT
275
276 if (SafepointTimeout)
277 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
278
279 // Iterate through all threads until it have been determined how to stop them all at a safepoint
280 unsigned int iterations = 0;
281 int steps = 0 ;
282 while(still_running > 0) {
283 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
284 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
285 ThreadSafepointState *cur_state = cur->safepoint_state();
286 if (cur_state->is_running()) {
287 cur_state->examine_state_of_thread();
288 if (!cur_state->is_running()) {
289 still_running--;
290 // consider adjusting steps downward:
291 // steps = 0
292 // steps -= NNN
293 // steps >>= 1
294 // steps = MIN(steps, 2000-100)
295 // if (iterations != 0) steps -= NNN
296 }
297 if (log_is_enabled(Trace, safepoint)) {
298 ResourceMark rm;
299 cur_state->print_on(Log(safepoint)::trace_stream());
300 }
301 }
302 }
303
304 if (iterations == 0) {
305 initial_running = still_running;
306 if (PrintSafepointStatistics) {
307 begin_statistics(nof_threads, still_running);
308 }
309 }
310
311 if (still_running > 0) {
312 // Check for if it takes to long
313 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
314 print_safepoint_timeout(_spinning_timeout);
315 }
316
317 // Spin to avoid context switching.
318 // There's a tension between allowing the mutators to run (and rendezvous)
319 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
320 // a mutator might otherwise use profitably to reach a safepoint. Excessive
321 // spinning by the VM thread on a saturated system can increase rendezvous latency.
322 // Blocking or yielding incur their own penalties in the form of context switching
323 // and the resultant loss of $ residency.
324 //
325 // Further complicating matters is that yield() does not work as naively expected
326 // on many platforms -- yield() does not guarantee that any other ready threads
327 // will run. As such we revert to naked_short_sleep() after some number of iterations.
328 // nakes_short_sleep() is implemented as a short unconditional sleep.
329 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
330 // can actually increase the time it takes the VM thread to detect that a system-wide
331 // stop-the-world safepoint has been reached. In a pathological scenario such as that
332 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
333 // In that case the mutators will be stalled waiting for the safepoint to complete and the
334 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
335 // will eventually wake up and detect that all mutators are safe, at which point
336 // we'll again make progress.
337 //
338 // Beware too that that the VMThread typically runs at elevated priority.
339 // Its default priority is higher than the default mutator priority.
340 // Obviously, this complicates spinning.
341 //
342 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
343 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
344 //
345 // See the comments in synchronizer.cpp for additional remarks on spinning.
346 //
347 // In the future we might:
348 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
349 // This is tricky as the path used by a thread exiting the JVM (say on
350 // on JNI call-out) simply stores into its state field. The burden
351 // is placed on the VM thread, which must poll (spin).
352 // 2. Find something useful to do while spinning. If the safepoint is GC-related
353 // we might aggressively scan the stacks of threads that are already safe.
354 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
355 // If all the mutators are ONPROC there's no reason to sleep or yield.
356 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
357 // 5. Check system saturation. If the system is not fully saturated then
358 // simply spin and avoid sleep/yield.
359 // 6. As still-running mutators rendezvous they could unpark the sleeping
360 // VMthread. This works well for still-running mutators that become
361 // safe. The VMthread must still poll for mutators that call-out.
362 // 7. Drive the policy on time-since-begin instead of iterations.
363 // 8. Consider making the spin duration a function of the # of CPUs:
364 // Spin = (((ncpus-1) * M) + K) + F(still_running)
365 // Alternately, instead of counting iterations of the outer loop
366 // we could count the # of threads visited in the inner loop, above.
367 // 9. On windows consider using the return value from SwitchThreadTo()
368 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
369
370 if (int(iterations) == DeferPollingPageLoopCount) {
371 guarantee (PageArmed == 0, "invariant") ;
372 PageArmed = 1 ;
373 os::make_polling_page_unreadable();
374 }
375
376 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
377 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
378 ++steps ;
379 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
380 SpinPause() ; // MP-Polite spin
381 } else
382 if (steps < DeferThrSuspendLoopCount) {
383 os::naked_yield() ;
384 } else {
385 os::naked_short_sleep(1);
386 }
387
388 iterations ++ ;
389 }
390 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
391 }
392 assert(still_running == 0, "sanity check");
393
394 if (PrintSafepointStatistics) {
395 update_statistics_on_spin_end();
396 }
397
398 TRACE_ONLY(post_safepoint_synchronize_event(&sync_event,
399 safepoint_counter(),
400 initial_running,
401 _waiting_to_block,
402 iterations);)
403 }
404
405 // wait until all threads are stopped
406 {
407 TRACE_ONLY(EventSafepointWaitBlocked wait_blocked_event;)
408 int initial_waiting_to_block = _waiting_to_block;
409
410 while (_waiting_to_block > 0) {
411 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
412 if (!SafepointTimeout || timeout_error_printed) {
413 Safepoint_lock->wait(true); // true, means with no safepoint checks
414 } else {
415 // Compute remaining time
416 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
417
418 // If there is no remaining time, then there is an error
419 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
420 print_safepoint_timeout(_blocking_timeout);
421 }
422 }
423 }
424 assert(_waiting_to_block == 0, "sanity check");
425
426 #ifndef PRODUCT
427 if (SafepointTimeout) {
428 jlong current_time = os::javaTimeNanos();
429 if (safepoint_limit_time < current_time) {
430 tty->print_cr("# SafepointSynchronize: Finished after "
431 INT64_FORMAT_W(6) " ms",
432 ((current_time - safepoint_limit_time) / MICROUNITS +
433 (jlong)SafepointTimeoutDelay));
434 }
435 }
436 #endif
437
438 assert((_safepoint_counter & 0x1) == 0, "must be even");
439 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
440 _safepoint_counter ++;
441
442 // Record state
443 _state = _synchronized;
444
445 OrderAccess::fence();
446
447 TRACE_ONLY(post_safepoint_wait_blocked_event(&wait_blocked_event,
448 safepoint_counter(),
449 initial_waiting_to_block);)
450 }
451
452 #ifdef ASSERT
453 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
454 // make sure all the threads were visited
455 assert(cur->was_visited_for_critical_count(), "missed a thread");
456 }
457 #endif // ASSERT
458
459 // Update the count of active JNI critical regions
460 GCLocker::set_jni_lock_count(_current_jni_active_count);
461
462 if (log_is_enabled(Debug, safepoint)) {
463 log_debug(safepoint)("Entering safepoint region: %s", VMThread::vm_safepoint_description());
464 }
465
466 RuntimeService::record_safepoint_synchronized();
467 if (PrintSafepointStatistics) {
468 update_statistics_on_sync_end(os::javaTimeNanos());
469 }
470
471 // Call stuff that needs to be run when a safepoint is just about to be completed
472 {
473 TRACE_ONLY(EventSafepointCleanup cleanup_event;)
474 do_cleanup_tasks();
475 TRACE_ONLY(post_safepoint_cleanup_event(&cleanup_event, safepoint_counter());)
476 }
477
478 if (PrintSafepointStatistics) {
479 // Record how much time spend on the above cleanup tasks
480 update_statistics_on_cleanup_end(os::javaTimeNanos());
481 }
482 TRACE_ONLY(post_safepoint_begin_event(&begin_event, safepoint_counter(),
483 nof_threads, _current_jni_active_count);)
484 }
485
486 // Wake up all threads, so they are ready to resume execution after the safepoint
487 // operation has been carried out
488 void SafepointSynchronize::end() {
489 TRACE_ONLY(EventSafepointEnd event;)
490 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id"
491
492 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
493 assert((_safepoint_counter & 0x1) == 1, "must be odd");
494 _safepoint_counter ++;
495 // memory fence isn't required here since an odd _safepoint_counter
496 // value can do no harm and a fence is issued below anyway.
497
498 DEBUG_ONLY(Thread* myThread = Thread::current();)
499 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
500
501 if (PrintSafepointStatistics) {
502 end_statistics(os::javaTimeNanos());
503 }
504
505 #ifdef ASSERT
506 // A pending_exception cannot be installed during a safepoint. The threads
507 // may install an async exception after they come back from a safepoint into
508 // pending_exception after they unblock. But that should happen later.
509 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
510 assert (!(cur->has_pending_exception() &&
511 cur->safepoint_state()->is_at_poll_safepoint()),
512 "safepoint installed a pending exception");
513 }
514 #endif // ASSERT
515
516 if (PageArmed) {
517 // Make polling safepoint aware
518 os::make_polling_page_readable();
519 PageArmed = 0 ;
520 }
521
522 // Remove safepoint check from interpreter
523 Interpreter::ignore_safepoints();
524
525 {
526 MutexLocker mu(Safepoint_lock);
527
528 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
529
530 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
531 // when they get restarted.
532 _state = _not_synchronized;
533 OrderAccess::fence();
534
535 log_debug(safepoint)("Leaving safepoint region");
536
537 // Start suspended threads
538 for(JavaThread *current = Threads::first(); current; current = current->next()) {
539 // A problem occurring on Solaris is when attempting to restart threads
540 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
541 // to the next one (since it has been running the longest). We then have
542 // to wait for a cpu to become available before we can continue restarting
543 // threads.
544 // FIXME: This causes the performance of the VM to degrade when active and with
545 // large numbers of threads. Apparently this is due to the synchronous nature
546 // of suspending threads.
547 //
548 // TODO-FIXME: the comments above are vestigial and no longer apply.
549 // Furthermore, using solaris' schedctl in this particular context confers no benefit
550 if (VMThreadHintNoPreempt) {
551 os::hint_no_preempt();
552 }
553 ThreadSafepointState* cur_state = current->safepoint_state();
554 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
555 cur_state->restart();
556 assert(cur_state->is_running(), "safepoint state has not been reset");
557 }
558
559 RuntimeService::record_safepoint_end();
560
561 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
562 // blocked in signal_thread_blocked
563 Threads_lock->unlock();
564
565 }
566 #if INCLUDE_ALL_GCS
567 // If there are any concurrent GC threads resume them.
568 if (UseConcMarkSweepGC) {
569 ConcurrentMarkSweepThread::desynchronize(false);
570 } else if (UseG1GC) {
571 SuspendibleThreadSet::desynchronize();
572 }
573 #endif // INCLUDE_ALL_GCS
574 // record this time so VMThread can keep track how much time has elapsed
575 // since last safepoint.
576 _end_of_last_safepoint = os::javaTimeMillis();
577
578 TRACE_ONLY(post_safepoint_end_event(&event, safepoint_id);)
579 }
580
581 bool SafepointSynchronize::is_cleanup_needed() {
582 // Need a safepoint if there are many monitors to deflate.
583 if (ObjectSynchronizer::is_cleanup_needed()) return true;
584 // Need a safepoint if some inline cache buffers is non-empty
585 if (!InlineCacheBuffer::is_empty()) return true;
586 return false;
587 }
588
589 // Various cleaning tasks that should be done periodically at safepoints
590 void SafepointSynchronize::do_cleanup_tasks() {
591 {
592 const char* name = "deflating idle monitors";
593 TRACE_ONLY(EventSafepointCleanupTask event;)
594 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
595 ObjectSynchronizer::deflate_idle_monitors();
596 TRACE_ONLY(post_safepoint_cleanup_task_event(&event, safepoint_counter(), name);)
597 }
598
599 {
600 const char* name = "updating inline caches";
601 TRACE_ONLY(EventSafepointCleanupTask event;)
602 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
603 InlineCacheBuffer::update_inline_caches();
604 TRACE_ONLY(post_safepoint_cleanup_task_event(&event, safepoint_counter(), name);)
605 }
606 {
607 const char* name = "compilation policy safepoint handler";
608 TRACE_ONLY(EventSafepointCleanupTask event;)
609 TraceTime timer("compilation policy safepoint handler", TRACETIME_LOG(Info, safepoint, cleanup));
610 CompilationPolicy::policy()->do_safepoint_work();
611 TRACE_ONLY(post_safepoint_cleanup_task_event(&event, safepoint_counter(), name);)
612 }
613
614 {
615 const char* name = "mark nmethods";
616 TRACE_ONLY(EventSafepointCleanupTask event;)
617 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
618 NMethodSweeper::mark_active_nmethods();
619 TRACE_ONLY(post_safepoint_cleanup_task_event(&event, safepoint_counter(), name);)
620 }
621
622 if (SymbolTable::needs_rehashing()) {
623 const char* name = "rehashing symbol table";
624 TRACE_ONLY(EventSafepointCleanupTask event;)
625 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
626 SymbolTable::rehash_table();
627 TRACE_ONLY(post_safepoint_cleanup_task_event(&event, safepoint_counter(), name);)
628 }
629
630 if (StringTable::needs_rehashing()) {
631 const char* name = "rehashing string table";
632 TRACE_ONLY(EventSafepointCleanupTask event;)
633 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
634 StringTable::rehash_table();
635 TRACE_ONLY(post_safepoint_cleanup_task_event(&event, safepoint_counter(), name);)
636 }
637
638 {
639 // CMS delays purging the CLDG until the beginning of the next safepoint and to
640 // make sure concurrent sweep is done
641 const char* name = "purging class loader data graph";
642 TRACE_ONLY(EventSafepointCleanupTask event;)
643 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
644 ClassLoaderDataGraph::purge_if_needed();
645 TRACE_ONLY(post_safepoint_cleanup_task_event(&event, safepoint_counter(), name);)
646 }
647 }
648
649
650 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
651 switch(state) {
652 case _thread_in_native:
653 // native threads are safe if they have no java stack or have walkable stack
654 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
655
656 // blocked threads should have already have walkable stack
657 case _thread_blocked:
658 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
659 return true;
660
661 default:
662 return false;
663 }
664 }
665
666
667 // See if the thread is running inside a lazy critical native and
668 // update the thread critical count if so. Also set a suspend flag to
669 // cause the native wrapper to return into the JVM to do the unlock
670 // once the native finishes.
671 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
672 if (state == _thread_in_native &&
673 thread->has_last_Java_frame() &&
674 thread->frame_anchor()->walkable()) {
675 // This thread might be in a critical native nmethod so look at
676 // the top of the stack and increment the critical count if it
677 // is.
678 frame wrapper_frame = thread->last_frame();
679 CodeBlob* stub_cb = wrapper_frame.cb();
680 if (stub_cb != NULL &&
681 stub_cb->is_nmethod() &&
682 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
683 // A thread could potentially be in a critical native across
684 // more than one safepoint, so only update the critical state on
685 // the first one. When it returns it will perform the unlock.
686 if (!thread->do_critical_native_unlock()) {
687 #ifdef ASSERT
688 if (!thread->in_critical()) {
689 GCLocker::increment_debug_jni_lock_count();
690 }
691 #endif
692 thread->enter_critical();
693 // Make sure the native wrapper calls back on return to
694 // perform the needed critical unlock.
695 thread->set_critical_native_unlock();
696 }
697 }
698 }
699 }
700
701
702
703 // -------------------------------------------------------------------------------------------------------
704 // Implementation of Safepoint callback point
705
706 void SafepointSynchronize::block(JavaThread *thread) {
707 assert(thread != NULL, "thread must be set");
708 assert(thread->is_Java_thread(), "not a Java thread");
709
710 // Threads shouldn't block if they are in the middle of printing, but...
711 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
712
713 // Only bail from the block() call if the thread is gone from the
714 // thread list; starting to exit should still block.
715 if (thread->is_terminated()) {
716 // block current thread if we come here from native code when VM is gone
717 thread->block_if_vm_exited();
718
719 // otherwise do nothing
720 return;
721 }
722
723 JavaThreadState state = thread->thread_state();
724 thread->frame_anchor()->make_walkable(thread);
725
726 // Check that we have a valid thread_state at this point
727 switch(state) {
728 case _thread_in_vm_trans:
729 case _thread_in_Java: // From compiled code
730
731 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
732 // we pretend we are still in the VM.
733 thread->set_thread_state(_thread_in_vm);
734
735 if (is_synchronizing()) {
736 Atomic::inc (&TryingToBlock) ;
737 }
738
739 // We will always be holding the Safepoint_lock when we are examine the state
740 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
741 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
742 Safepoint_lock->lock_without_safepoint_check();
743 if (is_synchronizing()) {
744 // Decrement the number of threads to wait for and signal vm thread
745 assert(_waiting_to_block > 0, "sanity check");
746 _waiting_to_block--;
747 thread->safepoint_state()->set_has_called_back(true);
748
749 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
750 if (thread->in_critical()) {
751 // Notice that this thread is in a critical section
752 increment_jni_active_count();
753 }
754
755 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
756 if (_waiting_to_block == 0) {
757 Safepoint_lock->notify_all();
758 }
759 }
760
761 // We transition the thread to state _thread_blocked here, but
762 // we can't do our usual check for external suspension and then
763 // self-suspend after the lock_without_safepoint_check() call
764 // below because we are often called during transitions while
765 // we hold different locks. That would leave us suspended while
766 // holding a resource which results in deadlocks.
767 thread->set_thread_state(_thread_blocked);
768 Safepoint_lock->unlock();
769
770 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
771 // the entire safepoint, the threads will all line up here during the safepoint.
772 Threads_lock->lock_without_safepoint_check();
773 // restore original state. This is important if the thread comes from compiled code, so it
774 // will continue to execute with the _thread_in_Java state.
775 thread->set_thread_state(state);
776 Threads_lock->unlock();
777 break;
778
779 case _thread_in_native_trans:
780 case _thread_blocked_trans:
781 case _thread_new_trans:
782 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
783 thread->print_thread_state();
784 fatal("Deadlock in safepoint code. "
785 "Should have called back to the VM before blocking.");
786 }
787
788 // We transition the thread to state _thread_blocked here, but
789 // we can't do our usual check for external suspension and then
790 // self-suspend after the lock_without_safepoint_check() call
791 // below because we are often called during transitions while
792 // we hold different locks. That would leave us suspended while
793 // holding a resource which results in deadlocks.
794 thread->set_thread_state(_thread_blocked);
795
796 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
797 // the safepoint code might still be waiting for it to block. We need to change the state here,
798 // so it can see that it is at a safepoint.
799
800 // Block until the safepoint operation is completed.
801 Threads_lock->lock_without_safepoint_check();
802
803 // Restore state
804 thread->set_thread_state(state);
805
806 Threads_lock->unlock();
807 break;
808
809 default:
810 fatal("Illegal threadstate encountered: %d", state);
811 }
812
813 // Check for pending. async. exceptions or suspends - except if the
814 // thread was blocked inside the VM. has_special_runtime_exit_condition()
815 // is called last since it grabs a lock and we only want to do that when
816 // we must.
817 //
818 // Note: we never deliver an async exception at a polling point as the
819 // compiler may not have an exception handler for it. The polling
820 // code will notice the async and deoptimize and the exception will
821 // be delivered. (Polling at a return point is ok though). Sure is
822 // a lot of bother for a deprecated feature...
823 //
824 // We don't deliver an async exception if the thread state is
825 // _thread_in_native_trans so JNI functions won't be called with
826 // a surprising pending exception. If the thread state is going back to java,
827 // async exception is checked in check_special_condition_for_native_trans().
828
829 if (state != _thread_blocked_trans &&
830 state != _thread_in_vm_trans &&
831 thread->has_special_runtime_exit_condition()) {
832 thread->handle_special_runtime_exit_condition(
833 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
834 }
835 }
836
837 // ------------------------------------------------------------------------------------------------------
838 // Exception handlers
839
840
841 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
842 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
843 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
844 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
845
846 if (ShowSafepointMsgs) {
847 tty->print("handle_polling_page_exception: ");
848 }
849
850 if (PrintSafepointStatistics) {
851 inc_page_trap_count();
852 }
853
854 ThreadSafepointState* state = thread->safepoint_state();
855
856 state->handle_polling_page_exception();
857 }
858
859
860 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
861 if (!timeout_error_printed) {
862 timeout_error_printed = true;
863 // Print out the thread info which didn't reach the safepoint for debugging
864 // purposes (useful when there are lots of threads in the debugger).
865 tty->cr();
866 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
867 if (reason == _spinning_timeout) {
868 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
869 } else if (reason == _blocking_timeout) {
870 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
871 }
872
873 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
874 ThreadSafepointState *cur_state;
875 ResourceMark rm;
876 for(JavaThread *cur_thread = Threads::first(); cur_thread;
877 cur_thread = cur_thread->next()) {
878 cur_state = cur_thread->safepoint_state();
879
880 if (cur_thread->thread_state() != _thread_blocked &&
881 ((reason == _spinning_timeout && cur_state->is_running()) ||
882 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
883 tty->print("# ");
884 cur_thread->print();
885 tty->cr();
886 }
887 }
888 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
889 }
890
891 // To debug the long safepoint, specify both DieOnSafepointTimeout &
892 // ShowMessageBoxOnError.
893 if (DieOnSafepointTimeout) {
894 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
895 SafepointTimeoutDelay, VMThread::vm_safepoint_description());
896 }
897 }
898
899
900 // -------------------------------------------------------------------------------------------------------
901 // Implementation of ThreadSafepointState
902
903 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
904 _thread = thread;
905 _type = _running;
906 _has_called_back = false;
907 _at_poll_safepoint = false;
908 }
909
910 void ThreadSafepointState::create(JavaThread *thread) {
911 ThreadSafepointState *state = new ThreadSafepointState(thread);
912 thread->set_safepoint_state(state);
913 }
914
915 void ThreadSafepointState::destroy(JavaThread *thread) {
916 if (thread->safepoint_state()) {
917 delete(thread->safepoint_state());
918 thread->set_safepoint_state(NULL);
919 }
920 }
921
922 void ThreadSafepointState::examine_state_of_thread() {
923 assert(is_running(), "better be running or just have hit safepoint poll");
924
925 JavaThreadState state = _thread->thread_state();
926
927 // Save the state at the start of safepoint processing.
928 _orig_thread_state = state;
929
930 // Check for a thread that is suspended. Note that thread resume tries
931 // to grab the Threads_lock which we own here, so a thread cannot be
932 // resumed during safepoint synchronization.
933
934 // We check to see if this thread is suspended without locking to
935 // avoid deadlocking with a third thread that is waiting for this
936 // thread to be suspended. The third thread can notice the safepoint
937 // that we're trying to start at the beginning of its SR_lock->wait()
938 // call. If that happens, then the third thread will block on the
939 // safepoint while still holding the underlying SR_lock. We won't be
940 // able to get the SR_lock and we'll deadlock.
941 //
942 // We don't need to grab the SR_lock here for two reasons:
943 // 1) The suspend flags are both volatile and are set with an
944 // Atomic::cmpxchg() call so we should see the suspended
945 // state right away.
946 // 2) We're being called from the safepoint polling loop; if
947 // we don't see the suspended state on this iteration, then
948 // we'll come around again.
949 //
950 bool is_suspended = _thread->is_ext_suspended();
951 if (is_suspended) {
952 roll_forward(_at_safepoint);
953 return;
954 }
955
956 // Some JavaThread states have an initial safepoint state of
957 // running, but are actually at a safepoint. We will happily
958 // agree and update the safepoint state here.
959 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
960 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
961 roll_forward(_at_safepoint);
962 return;
963 }
964
965 if (state == _thread_in_vm) {
966 roll_forward(_call_back);
967 return;
968 }
969
970 // All other thread states will continue to run until they
971 // transition and self-block in state _blocked
972 // Safepoint polling in compiled code causes the Java threads to do the same.
973 // Note: new threads may require a malloc so they must be allowed to finish
974
975 assert(is_running(), "examine_state_of_thread on non-running thread");
976 return;
977 }
978
979 // Returns true is thread could not be rolled forward at present position.
980 void ThreadSafepointState::roll_forward(suspend_type type) {
981 _type = type;
982
983 switch(_type) {
984 case _at_safepoint:
985 SafepointSynchronize::signal_thread_at_safepoint();
986 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
987 if (_thread->in_critical()) {
988 // Notice that this thread is in a critical section
989 SafepointSynchronize::increment_jni_active_count();
990 }
991 break;
992
993 case _call_back:
994 set_has_called_back(false);
995 break;
996
997 case _running:
998 default:
999 ShouldNotReachHere();
1000 }
1001 }
1002
1003 void ThreadSafepointState::restart() {
1004 switch(type()) {
1005 case _at_safepoint:
1006 case _call_back:
1007 break;
1008
1009 case _running:
1010 default:
1011 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
1012 p2i(_thread), _type);
1013 _thread->print();
1014 ShouldNotReachHere();
1015 }
1016 _type = _running;
1017 set_has_called_back(false);
1018 }
1019
1020
1021 void ThreadSafepointState::print_on(outputStream *st) const {
1022 const char *s = NULL;
1023
1024 switch(_type) {
1025 case _running : s = "_running"; break;
1026 case _at_safepoint : s = "_at_safepoint"; break;
1027 case _call_back : s = "_call_back"; break;
1028 default:
1029 ShouldNotReachHere();
1030 }
1031
1032 st->print_cr("Thread: " INTPTR_FORMAT
1033 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1034 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
1035 _at_poll_safepoint);
1036
1037 _thread->print_thread_state_on(st);
1038 }
1039
1040 // ---------------------------------------------------------------------------------------------------------------------
1041
1042 // Block the thread at the safepoint poll or poll return.
1043 void ThreadSafepointState::handle_polling_page_exception() {
1044
1045 // Check state. block() will set thread state to thread_in_vm which will
1046 // cause the safepoint state _type to become _call_back.
1047 assert(type() == ThreadSafepointState::_running,
1048 "polling page exception on thread not running state");
1049
1050 // Step 1: Find the nmethod from the return address
1051 if (ShowSafepointMsgs && Verbose) {
1052 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
1053 }
1054 address real_return_addr = thread()->saved_exception_pc();
1055
1056 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1057 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1058 CompiledMethod* nm = (CompiledMethod*)cb;
1059
1060 // Find frame of caller
1061 frame stub_fr = thread()->last_frame();
1062 CodeBlob* stub_cb = stub_fr.cb();
1063 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1064 RegisterMap map(thread(), true);
1065 frame caller_fr = stub_fr.sender(&map);
1066
1067 // Should only be poll_return or poll
1068 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1069
1070 // This is a poll immediately before a return. The exception handling code
1071 // has already had the effect of causing the return to occur, so the execution
1072 // will continue immediately after the call. In addition, the oopmap at the
1073 // return point does not mark the return value as an oop (if it is), so
1074 // it needs a handle here to be updated.
1075 if( nm->is_at_poll_return(real_return_addr) ) {
1076 // See if return type is an oop.
1077 bool return_oop = nm->method()->is_returning_oop();
1078 Handle return_value;
1079 if (return_oop) {
1080 // The oop result has been saved on the stack together with all
1081 // the other registers. In order to preserve it over GCs we need
1082 // to keep it in a handle.
1083 oop result = caller_fr.saved_oop_result(&map);
1084 assert(result == NULL || result->is_oop(), "must be oop");
1085 return_value = Handle(thread(), result);
1086 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1087 }
1088
1089 // Block the thread
1090 SafepointSynchronize::block(thread());
1091
1092 // restore oop result, if any
1093 if (return_oop) {
1094 caller_fr.set_saved_oop_result(&map, return_value());
1095 }
1096 }
1097
1098 // This is a safepoint poll. Verify the return address and block.
1099 else {
1100 set_at_poll_safepoint(true);
1101
1102 // verify the blob built the "return address" correctly
1103 assert(real_return_addr == caller_fr.pc(), "must match");
1104
1105 // Block the thread
1106 SafepointSynchronize::block(thread());
1107 set_at_poll_safepoint(false);
1108
1109 // If we have a pending async exception deoptimize the frame
1110 // as otherwise we may never deliver it.
1111 if (thread()->has_async_condition()) {
1112 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1113 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1114 }
1115
1116 // If an exception has been installed we must check for a pending deoptimization
1117 // Deoptimize frame if exception has been thrown.
1118
1119 if (thread()->has_pending_exception() ) {
1120 RegisterMap map(thread(), true);
1121 frame caller_fr = stub_fr.sender(&map);
1122 if (caller_fr.is_deoptimized_frame()) {
1123 // The exception patch will destroy registers that are still
1124 // live and will be needed during deoptimization. Defer the
1125 // Async exception should have deferred the exception until the
1126 // next safepoint which will be detected when we get into
1127 // the interpreter so if we have an exception now things
1128 // are messed up.
1129
1130 fatal("Exception installed and deoptimization is pending");
1131 }
1132 }
1133 }
1134 }
1135
1136
1137 //
1138 // Statistics & Instrumentations
1139 //
1140 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1141 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1142 int SafepointSynchronize::_cur_stat_index = 0;
1143 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1144 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1145 jlong SafepointSynchronize::_max_sync_time = 0;
1146 jlong SafepointSynchronize::_max_vmop_time = 0;
1147 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1148
1149 static jlong cleanup_end_time = 0;
1150 static bool need_to_track_page_armed_status = false;
1151 static bool init_done = false;
1152
1153 // Helper method to print the header.
1154 static void print_header() {
1155 // The number of spaces is significant here, and should match the format
1156 // specifiers in print_statistics().
1157
1158 tty->print(" vmop "
1159 "[ threads: total initially_running wait_to_block ]"
1160 "[ time: spin block sync cleanup vmop ] ");
1161
1162 // no page armed status printed out if it is always armed.
1163 if (need_to_track_page_armed_status) {
1164 tty->print("page_armed ");
1165 }
1166
1167 tty->print_cr("page_trap_count");
1168 }
1169
1170 void SafepointSynchronize::deferred_initialize_stat() {
1171 if (init_done) return;
1172
1173 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1174 // be printed right away, in which case, _safepoint_stats will regress to
1175 // a single element array. Otherwise, it is a circular ring buffer with default
1176 // size of PrintSafepointStatisticsCount.
1177 int stats_array_size;
1178 if (PrintSafepointStatisticsTimeout > 0) {
1179 stats_array_size = 1;
1180 PrintSafepointStatistics = true;
1181 } else {
1182 stats_array_size = PrintSafepointStatisticsCount;
1183 }
1184 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1185 * sizeof(SafepointStats), mtInternal);
1186 guarantee(_safepoint_stats != NULL,
1187 "not enough memory for safepoint instrumentation data");
1188
1189 if (DeferPollingPageLoopCount >= 0) {
1190 need_to_track_page_armed_status = true;
1191 }
1192 init_done = true;
1193 }
1194
1195 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1196 assert(init_done, "safepoint statistics array hasn't been initialized");
1197 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1198
1199 spstat->_time_stamp = _ts_of_current_safepoint;
1200
1201 VM_Operation *op = VMThread::vm_operation();
1202 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1203 if (op != NULL) {
1204 _safepoint_reasons[spstat->_vmop_type]++;
1205 }
1206
1207 spstat->_nof_total_threads = nof_threads;
1208 spstat->_nof_initial_running_threads = nof_running;
1209 spstat->_nof_threads_hit_page_trap = 0;
1210
1211 // Records the start time of spinning. The real time spent on spinning
1212 // will be adjusted when spin is done. Same trick is applied for time
1213 // spent on waiting for threads to block.
1214 if (nof_running != 0) {
1215 spstat->_time_to_spin = os::javaTimeNanos();
1216 } else {
1217 spstat->_time_to_spin = 0;
1218 }
1219 }
1220
1221 void SafepointSynchronize::update_statistics_on_spin_end() {
1222 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1223
1224 jlong cur_time = os::javaTimeNanos();
1225
1226 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1227 if (spstat->_nof_initial_running_threads != 0) {
1228 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1229 }
1230
1231 if (need_to_track_page_armed_status) {
1232 spstat->_page_armed = (PageArmed == 1);
1233 }
1234
1235 // Records the start time of waiting for to block. Updated when block is done.
1236 if (_waiting_to_block != 0) {
1237 spstat->_time_to_wait_to_block = cur_time;
1238 } else {
1239 spstat->_time_to_wait_to_block = 0;
1240 }
1241 }
1242
1243 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1244 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1245
1246 if (spstat->_nof_threads_wait_to_block != 0) {
1247 spstat->_time_to_wait_to_block = end_time -
1248 spstat->_time_to_wait_to_block;
1249 }
1250
1251 // Records the end time of sync which will be used to calculate the total
1252 // vm operation time. Again, the real time spending in syncing will be deducted
1253 // from the start of the sync time later when end_statistics is called.
1254 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1255 if (spstat->_time_to_sync > _max_sync_time) {
1256 _max_sync_time = spstat->_time_to_sync;
1257 }
1258
1259 spstat->_time_to_do_cleanups = end_time;
1260 }
1261
1262 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1263 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1264
1265 // Record how long spent in cleanup tasks.
1266 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1267
1268 cleanup_end_time = end_time;
1269 }
1270
1271 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1272 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1273
1274 // Update the vm operation time.
1275 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1276 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1277 _max_vmop_time = spstat->_time_to_exec_vmop;
1278 }
1279 // Only the sync time longer than the specified
1280 // PrintSafepointStatisticsTimeout will be printed out right away.
1281 // By default, it is -1 meaning all samples will be put into the list.
1282 if ( PrintSafepointStatisticsTimeout > 0) {
1283 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1284 print_statistics();
1285 }
1286 } else {
1287 // The safepoint statistics will be printed out when the _safepoin_stats
1288 // array fills up.
1289 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1290 print_statistics();
1291 _cur_stat_index = 0;
1292 } else {
1293 _cur_stat_index++;
1294 }
1295 }
1296 }
1297
1298 void SafepointSynchronize::print_statistics() {
1299 for (int index = 0; index <= _cur_stat_index; index++) {
1300 if (index % 30 == 0) {
1301 print_header();
1302 }
1303 SafepointStats* sstats = &_safepoint_stats[index];
1304 tty->print("%8.3f: ", sstats->_time_stamp);
1305 tty->print("%-30s [ "
1306 INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " "
1307 "]",
1308 (sstats->_vmop_type == -1 ? "no vm operation" : VM_Operation::name(sstats->_vmop_type)),
1309 sstats->_nof_total_threads,
1310 sstats->_nof_initial_running_threads,
1311 sstats->_nof_threads_wait_to_block);
1312 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1313 tty->print("[ "
1314 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1315 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1316 INT64_FORMAT_W(7) " ] ",
1317 sstats->_time_to_spin / MICROUNITS,
1318 sstats->_time_to_wait_to_block / MICROUNITS,
1319 sstats->_time_to_sync / MICROUNITS,
1320 sstats->_time_to_do_cleanups / MICROUNITS,
1321 sstats->_time_to_exec_vmop / MICROUNITS);
1322
1323 if (need_to_track_page_armed_status) {
1324 tty->print(INT32_FORMAT_W(10) " ", sstats->_page_armed);
1325 }
1326 tty->print_cr(INT32_FORMAT_W(15) " ", sstats->_nof_threads_hit_page_trap);
1327 }
1328 }
1329
1330 // This method will be called when VM exits. It will first call
1331 // print_statistics to print out the rest of the sampling. Then
1332 // it tries to summarize the sampling.
1333 void SafepointSynchronize::print_stat_on_exit() {
1334 if (_safepoint_stats == NULL) return;
1335
1336 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1337
1338 // During VM exit, end_statistics may not get called and in that
1339 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1340 // don't print it out.
1341 // Approximate the vm op time.
1342 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1343 os::javaTimeNanos() - cleanup_end_time;
1344
1345 if ( PrintSafepointStatisticsTimeout < 0 ||
1346 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1347 print_statistics();
1348 }
1349 tty->cr();
1350
1351 // Print out polling page sampling status.
1352 if (!need_to_track_page_armed_status) {
1353 tty->print_cr("Polling page always armed");
1354 } else {
1355 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
1356 DeferPollingPageLoopCount);
1357 }
1358
1359 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1360 if (_safepoint_reasons[index] != 0) {
1361 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1362 _safepoint_reasons[index]);
1363 }
1364 }
1365
1366 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1367 _coalesced_vmop_count);
1368 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1369 _max_sync_time / MICROUNITS);
1370 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1371 INT64_FORMAT_W(5) " ms",
1372 _max_vmop_time / MICROUNITS);
1373 }
1374
1375 // ------------------------------------------------------------------------------------------------
1376 // Non-product code
1377
1378 #ifndef PRODUCT
1379
1380 void SafepointSynchronize::print_state() {
1381 if (_state == _not_synchronized) {
1382 tty->print_cr("not synchronized");
1383 } else if (_state == _synchronizing || _state == _synchronized) {
1384 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1385 "synchronized");
1386
1387 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1388 cur->safepoint_state()->print();
1389 }
1390 }
1391 }
1392
1393 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1394 if (ShowSafepointMsgs) {
1395 va_list ap;
1396 va_start(ap, format);
1397 tty->vprint_cr(format, ap);
1398 va_end(ap);
1399 }
1400 }
1401
1402 #endif // !PRODUCT