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/classLoaderData.hpp"
27 #include "classfile/stringTable.hpp"
28 #include "classfile/symbolTable.hpp"
29 #include "classfile/systemDictionary.hpp"
30 #include "code/codeCache.hpp"
31 #include "code/icBuffer.hpp"
32 #include "code/nmethod.hpp"
33 #include "code/pcDesc.hpp"
34 #include "code/scopeDesc.hpp"
35 #include "gc/shared/collectedHeap.hpp"
36 #include "gc/shared/gcLocker.inline.hpp"
37 #include "gc/shared/strongRootsScope.hpp"
38 #include "gc/shared/workgroup.hpp"
39 #include "interpreter/interpreter.hpp"
40 #include "logging/log.hpp"
41 #include "logging/logStream.hpp"
42 #include "memory/resourceArea.hpp"
43 #include "memory/universe.inline.hpp"
44 #include "oops/oop.inline.hpp"
45 #include "oops/symbol.hpp"
46 #include "runtime/atomic.hpp"
47 #include "runtime/compilationPolicy.hpp"
48 #include "runtime/deoptimization.hpp"
49 #include "runtime/frame.inline.hpp"
50 #include "runtime/interfaceSupport.hpp"
51 #include "runtime/mutexLocker.hpp"
52 #include "runtime/orderAccess.inline.hpp"
53 #include "runtime/osThread.hpp"
54 #include "runtime/safepoint.hpp"
55 #include "runtime/safepointMechanism.inline.hpp"
56 #include "runtime/signature.hpp"
57 #include "runtime/stubCodeGenerator.hpp"
58 #include "runtime/stubRoutines.hpp"
59 #include "runtime/sweeper.hpp"
60 #include "runtime/synchronizer.hpp"
61 #include "runtime/thread.inline.hpp"
62 #include "runtime/timerTrace.hpp"
63 #include "services/runtimeService.hpp"
64 #include "trace/tracing.hpp"
65 #include "trace/traceMacros.hpp"
66 #include "utilities/events.hpp"
67 #include "utilities/macros.hpp"
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 Universe::heap()->safepoint_synchronize_begin();
96
97 // By getting the Threads_lock, we assure that no threads are about to start or
98 // exit. It is released again in SafepointSynchronize::end().
99 Threads_lock->lock();
100
101 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
102
103 int nof_threads = Threads::number_of_threads();
104
105 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads);
106
107 RuntimeService::record_safepoint_begin();
108
109 MutexLocker mu(Safepoint_lock);
110
111 // Reset the count of active JNI critical threads
112 _current_jni_active_count = 0;
113
114 // Set number of threads to wait for, before we initiate the callbacks
115 _waiting_to_block = nof_threads;
116 TryingToBlock = 0 ;
117 int still_running = nof_threads;
118
119 // Save the starting time, so that it can be compared to see if this has taken
120 // too long to complete.
121 jlong safepoint_limit_time = 0;
122 timeout_error_printed = false;
123
124 // PrintSafepointStatisticsTimeout can be specified separately. When
125 // specified, PrintSafepointStatistics will be set to true in
126 // deferred_initialize_stat method. The initialization has to be done
127 // early enough to avoid any races. See bug 6880029 for details.
128 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
129 deferred_initialize_stat();
130 }
131
132 // Begin the process of bringing the system to a safepoint.
133 // Java threads can be in several different states and are
134 // stopped by different mechanisms:
135 //
136 // 1. Running interpreted
137 // The interpreter dispatch table is changed to force it to
138 // check for a safepoint condition between bytecodes.
139 // 2. Running in native code
140 // When returning from the native code, a Java thread must check
141 // the safepoint _state to see if we must block. If the
142 // VM thread sees a Java thread in native, it does
143 // not wait for this thread to block. The order of the memory
144 // writes and reads of both the safepoint state and the Java
145 // threads state is critical. In order to guarantee that the
146 // memory writes are serialized with respect to each other,
147 // the VM thread issues a memory barrier instruction
148 // (on MP systems). In order to avoid the overhead of issuing
149 // a memory barrier for each Java thread making native calls, each Java
150 // thread performs a write to a single memory page after changing
151 // the thread state. The VM thread performs a sequence of
152 // mprotect OS calls which forces all previous writes from all
153 // Java threads to be serialized. This is done in the
154 // os::serialize_thread_states() call. This has proven to be
155 // much more efficient than executing a membar instruction
156 // on every call to native code.
157 // 3. Running compiled Code
158 // Compiled code reads a global (Safepoint Polling) page that
159 // is set to fault if we are trying to get to a safepoint.
160 // 4. Blocked
161 // A thread which is blocked will not be allowed to return from the
162 // block condition until the safepoint operation is complete.
163 // 5. In VM or Transitioning between states
164 // If a Java thread is currently running in the VM or transitioning
165 // between states, the safepointing code will wait for the thread to
166 // block itself when it attempts transitions to a new state.
167 //
168 {
169 EventSafepointStateSynchronization sync_event;
170 int initial_running = 0;
171
172 _state = _synchronizing;
173
174 if (SafepointMechanism::uses_thread_local_poll()) {
175 // Arming the per thread poll while having _state != _not_synchronized means safepointing
176 log_trace(safepoint)("Setting thread local yield flag for threads");
177 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
178 // Make sure the threads start polling, it is time to yield.
179 SafepointMechanism::arm_local_poll(cur); // release store, global state -> local state
180 }
181 }
182 OrderAccess::fence(); // storestore|storeload, global state -> local state
183
184 // Flush all thread states to memory
185 if (!UseMembar) {
186 os::serialize_thread_states();
187 }
188
189 if (SafepointMechanism::uses_global_page_poll()) {
190 // Make interpreter safepoint aware
191 Interpreter::notice_safepoints();
192
193 if (DeferPollingPageLoopCount < 0) {
194 // Make polling safepoint aware
195 guarantee (PageArmed == 0, "invariant") ;
196 PageArmed = 1 ;
197 os::make_polling_page_unreadable();
198 }
199 }
200
201 // Consider using active_processor_count() ... but that call is expensive.
202 int ncpus = os::processor_count() ;
203
204 #ifdef ASSERT
205 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
206 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
207 // Clear the visited flag to ensure that the critical counts are collected properly.
208 cur->set_visited_for_critical_count(false);
209 }
210 #endif // ASSERT
211
212 if (SafepointTimeout)
213 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
214
215 // Iterate through all threads until it have been determined how to stop them all at a safepoint
216 unsigned int iterations = 0;
217 int steps = 0 ;
218 while(still_running > 0) {
219 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
220 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
221 ThreadSafepointState *cur_state = cur->safepoint_state();
222 if (cur_state->is_running()) {
223 cur_state->examine_state_of_thread();
224 if (!cur_state->is_running()) {
225 still_running--;
226 // consider adjusting steps downward:
227 // steps = 0
228 // steps -= NNN
229 // steps >>= 1
230 // steps = MIN(steps, 2000-100)
231 // if (iterations != 0) steps -= NNN
232 }
233 LogTarget(Trace, safepoint) lt;
234 if (lt.is_enabled()) {
235 ResourceMark rm;
236 LogStream ls(lt);
237 cur_state->print_on(&ls);
238 }
239 }
240 }
241
242 if (iterations == 0) {
243 initial_running = still_running;
244 if (PrintSafepointStatistics) {
245 begin_statistics(nof_threads, still_running);
246 }
247 }
248
249 if (still_running > 0) {
250 // Check for if it takes to long
251 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
252 print_safepoint_timeout(_spinning_timeout);
253 }
254
255 // Spin to avoid context switching.
256 // There's a tension between allowing the mutators to run (and rendezvous)
257 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
258 // a mutator might otherwise use profitably to reach a safepoint. Excessive
259 // spinning by the VM thread on a saturated system can increase rendezvous latency.
260 // Blocking or yielding incur their own penalties in the form of context switching
261 // and the resultant loss of $ residency.
262 //
263 // Further complicating matters is that yield() does not work as naively expected
264 // on many platforms -- yield() does not guarantee that any other ready threads
265 // will run. As such we revert to naked_short_sleep() after some number of iterations.
266 // nakes_short_sleep() is implemented as a short unconditional sleep.
267 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
268 // can actually increase the time it takes the VM thread to detect that a system-wide
269 // stop-the-world safepoint has been reached. In a pathological scenario such as that
270 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
271 // In that case the mutators will be stalled waiting for the safepoint to complete and the
272 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
273 // will eventually wake up and detect that all mutators are safe, at which point
274 // we'll again make progress.
275 //
276 // Beware too that that the VMThread typically runs at elevated priority.
277 // Its default priority is higher than the default mutator priority.
278 // Obviously, this complicates spinning.
279 //
280 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
281 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
282 //
283 // See the comments in synchronizer.cpp for additional remarks on spinning.
284 //
285 // In the future we might:
286 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
287 // This is tricky as the path used by a thread exiting the JVM (say on
288 // on JNI call-out) simply stores into its state field. The burden
289 // is placed on the VM thread, which must poll (spin).
290 // 2. Find something useful to do while spinning. If the safepoint is GC-related
291 // we might aggressively scan the stacks of threads that are already safe.
292 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
293 // If all the mutators are ONPROC there's no reason to sleep or yield.
294 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
295 // 5. Check system saturation. If the system is not fully saturated then
296 // simply spin and avoid sleep/yield.
297 // 6. As still-running mutators rendezvous they could unpark the sleeping
298 // VMthread. This works well for still-running mutators that become
299 // safe. The VMthread must still poll for mutators that call-out.
300 // 7. Drive the policy on time-since-begin instead of iterations.
301 // 8. Consider making the spin duration a function of the # of CPUs:
302 // Spin = (((ncpus-1) * M) + K) + F(still_running)
303 // Alternately, instead of counting iterations of the outer loop
304 // we could count the # of threads visited in the inner loop, above.
305 // 9. On windows consider using the return value from SwitchThreadTo()
306 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
307
308 if (SafepointMechanism::uses_global_page_poll() && int(iterations) == DeferPollingPageLoopCount) {
309 guarantee (PageArmed == 0, "invariant") ;
310 PageArmed = 1 ;
311 os::make_polling_page_unreadable();
312 }
313
314 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
315 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
316 ++steps ;
317 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
318 SpinPause() ; // MP-Polite spin
319 } else
320 if (steps < DeferThrSuspendLoopCount) {
321 os::naked_yield() ;
322 } else {
323 os::naked_short_sleep(1);
324 }
325
326 iterations ++ ;
327 }
328 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
329 }
330 assert(still_running == 0, "sanity check");
331
332 if (PrintSafepointStatistics) {
333 update_statistics_on_spin_end();
334 }
335
336 if (sync_event.should_commit()) {
337 // Group this event together with the ones committed after the counter is increased
338 sync_event.set_safepointId(safepoint_counter() + 1);
339 sync_event.set_initialThreadCount(initial_running);
340 sync_event.set_runningThreadCount(_waiting_to_block);
341 sync_event.set_iterations(iterations);
342 sync_event.commit();
343 }
344 } //EventSafepointStateSync
345
346 // wait until all threads are stopped
347 {
348 EventSafepointWaitBlocked wait_blocked_event;
349 int initial_waiting_to_block = _waiting_to_block;
350
351 while (_waiting_to_block > 0) {
352 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
353 if (!SafepointTimeout || timeout_error_printed) {
354 Safepoint_lock->wait(true); // true, means with no safepoint checks
355 } else {
356 // Compute remaining time
357 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
358
359 // If there is no remaining time, then there is an error
360 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
361 print_safepoint_timeout(_blocking_timeout);
362 }
363 }
364 }
365 assert(_waiting_to_block == 0, "sanity check");
366
367 #ifndef PRODUCT
368 if (SafepointTimeout) {
369 jlong current_time = os::javaTimeNanos();
370 if (safepoint_limit_time < current_time) {
371 tty->print_cr("# SafepointSynchronize: Finished after "
372 INT64_FORMAT_W(6) " ms",
373 (int64_t)((current_time - safepoint_limit_time) / MICROUNITS +
374 (jlong)SafepointTimeoutDelay));
375 }
376 }
377 #endif
378
379 assert((_safepoint_counter & 0x1) == 0, "must be even");
380 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
381 _safepoint_counter ++;
382
383 // Record state
384 _state = _synchronized;
385
386 OrderAccess::fence();
387
388 if (wait_blocked_event.should_commit()) {
389 wait_blocked_event.set_safepointId(safepoint_counter());
390 wait_blocked_event.set_runningThreadCount(initial_waiting_to_block);
391 wait_blocked_event.commit();
392 }
393 } // EventSafepointWaitBlocked
394
395 #ifdef ASSERT
396 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
397 // make sure all the threads were visited
398 assert(cur->was_visited_for_critical_count(), "missed a thread");
399 }
400 #endif // ASSERT
401
402 // Update the count of active JNI critical regions
403 GCLocker::set_jni_lock_count(_current_jni_active_count);
404
405 if (log_is_enabled(Debug, safepoint)) {
406 log_debug(safepoint)("Entering safepoint region: %s", VMThread::vm_safepoint_description());
407 }
408
409 RuntimeService::record_safepoint_synchronized();
410 if (PrintSafepointStatistics) {
411 update_statistics_on_sync_end(os::javaTimeNanos());
412 }
413
414 // Call stuff that needs to be run when a safepoint is just about to be completed
415 {
416 EventSafepointCleanup cleanup_event;
417 do_cleanup_tasks();
418 if (cleanup_event.should_commit()) {
419 cleanup_event.set_safepointId(safepoint_counter());
420 cleanup_event.commit();
421 }
422 }
423
424 if (PrintSafepointStatistics) {
425 // Record how much time spend on the above cleanup tasks
426 update_statistics_on_cleanup_end(os::javaTimeNanos());
427 }
428 if (begin_event.should_commit()) {
429 begin_event.set_safepointId(safepoint_counter());
430 begin_event.set_totalThreadCount(nof_threads);
431 begin_event.set_jniCriticalThreadCount(_current_jni_active_count);
432 begin_event.commit();
433 }
434 }
435
436 // Wake up all threads, so they are ready to resume execution after the safepoint
437 // operation has been carried out
438 void SafepointSynchronize::end() {
439 EventSafepointEnd event;
440 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id"
441
442 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
443 assert((_safepoint_counter & 0x1) == 1, "must be odd");
444 _safepoint_counter ++;
445 // memory fence isn't required here since an odd _safepoint_counter
446 // value can do no harm and a fence is issued below anyway.
447
448 DEBUG_ONLY(Thread* myThread = Thread::current();)
449 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
450
451 if (PrintSafepointStatistics) {
452 end_statistics(os::javaTimeNanos());
453 }
454
455 #ifdef ASSERT
456 // A pending_exception cannot be installed during a safepoint. The threads
457 // may install an async exception after they come back from a safepoint into
458 // pending_exception after they unblock. But that should happen later.
459 for (JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
460 assert (!(cur->has_pending_exception() &&
461 cur->safepoint_state()->is_at_poll_safepoint()),
462 "safepoint installed a pending exception");
463 }
464 #endif // ASSERT
465
466 if (PageArmed) {
467 assert(SafepointMechanism::uses_global_page_poll(), "sanity");
468 // Make polling safepoint aware
469 os::make_polling_page_readable();
470 PageArmed = 0 ;
471 }
472
473 if (SafepointMechanism::uses_global_page_poll()) {
474 // Remove safepoint check from interpreter
475 Interpreter::ignore_safepoints();
476 }
477
478 {
479 MutexLocker mu(Safepoint_lock);
480
481 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
482
483 if (SafepointMechanism::uses_thread_local_poll()) {
484 _state = _not_synchronized;
485 OrderAccess::storestore(); // global state -> local state
486 for (JavaThread *current = Threads::first(); current; current = current->next()) {
487 ThreadSafepointState* cur_state = current->safepoint_state();
488 cur_state->restart(); // TSS _running
489 SafepointMechanism::disarm_local_poll(current); // release store, local state -> polling page
490 }
491 log_debug(safepoint)("Leaving safepoint region");
492 } else {
493 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
494 // when they get restarted.
495 _state = _not_synchronized;
496 OrderAccess::fence();
497
498 log_debug(safepoint)("Leaving safepoint region");
499
500 // Start suspended threads
501 for (JavaThread *current = Threads::first(); current; current = current->next()) {
502 // A problem occurring on Solaris is when attempting to restart threads
503 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
504 // to the next one (since it has been running the longest). We then have
505 // to wait for a cpu to become available before we can continue restarting
506 // threads.
507 // FIXME: This causes the performance of the VM to degrade when active and with
508 // large numbers of threads. Apparently this is due to the synchronous nature
509 // of suspending threads.
510 //
511 // TODO-FIXME: the comments above are vestigial and no longer apply.
512 // Furthermore, using solaris' schedctl in this particular context confers no benefit
513 if (VMThreadHintNoPreempt) {
514 os::hint_no_preempt();
515 }
516 ThreadSafepointState* cur_state = current->safepoint_state();
517 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
518 cur_state->restart();
519 assert(cur_state->is_running(), "safepoint state has not been reset");
520 }
521 }
522
523 RuntimeService::record_safepoint_end();
524
525 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
526 // blocked in signal_thread_blocked
527 Threads_lock->unlock();
528
529 }
530 Universe::heap()->safepoint_synchronize_end();
531 // record this time so VMThread can keep track how much time has elapsed
532 // since last safepoint.
533 _end_of_last_safepoint = os::javaTimeMillis();
534
535 if (event.should_commit()) {
536 event.set_safepointId(safepoint_id);
537 event.commit();
538 }
539 }
540
541 bool SafepointSynchronize::is_cleanup_needed() {
542 // Need a safepoint if there are many monitors to deflate.
543 if (ObjectSynchronizer::is_cleanup_needed()) return true;
544 // Need a safepoint if some inline cache buffers is non-empty
545 if (!InlineCacheBuffer::is_empty()) return true;
546 return false;
547 }
548
549 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) {
550 if (event.should_commit()) {
551 event.set_safepointId(SafepointSynchronize::safepoint_counter());
552 event.set_name(name);
553 event.commit();
554 }
555 }
556
557 class ParallelSPCleanupThreadClosure : public ThreadClosure {
558 private:
559 CodeBlobClosure* _nmethod_cl;
560 DeflateMonitorCounters* _counters;
561
562 public:
563 ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) :
564 _counters(counters),
565 _nmethod_cl(NMethodSweeper::prepare_mark_active_nmethods()) {}
566
567 void do_thread(Thread* thread) {
568 ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters);
569 if (_nmethod_cl != NULL && thread->is_Java_thread() &&
570 ! thread->is_Code_cache_sweeper_thread()) {
571 JavaThread* jt = (JavaThread*) thread;
572 jt->nmethods_do(_nmethod_cl);
573 }
574 }
575 };
576
577 class ParallelSPCleanupTask : public AbstractGangTask {
578 private:
579 SubTasksDone _subtasks;
580 ParallelSPCleanupThreadClosure _cleanup_threads_cl;
581 uint _num_workers;
582 DeflateMonitorCounters* _counters;
583 public:
584 ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
585 AbstractGangTask("Parallel Safepoint Cleanup"),
586 _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
587 _num_workers(num_workers),
588 _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)),
589 _counters(counters) {}
590
591 void work(uint worker_id) {
592 // All threads deflate monitors and mark nmethods (if necessary).
593 Threads::possibly_parallel_threads_do(true, &_cleanup_threads_cl);
594
595 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
596 const char* name = "deflating idle monitors";
597 EventSafepointCleanupTask event;
598 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
599 ObjectSynchronizer::deflate_idle_monitors(_counters);
600 event_safepoint_cleanup_task_commit(event, name);
601 }
602
603 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
604 const char* name = "updating inline caches";
605 EventSafepointCleanupTask event;
606 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
607 InlineCacheBuffer::update_inline_caches();
608 event_safepoint_cleanup_task_commit(event, name);
609 }
610
611 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
612 const char* name = "compilation policy safepoint handler";
613 EventSafepointCleanupTask event;
614 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
615 CompilationPolicy::policy()->do_safepoint_work();
616 event_safepoint_cleanup_task_commit(event, name);
617 }
618
619 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
620 if (SymbolTable::needs_rehashing()) {
621 const char* name = "rehashing symbol table";
622 EventSafepointCleanupTask event;
623 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
624 SymbolTable::rehash_table();
625 event_safepoint_cleanup_task_commit(event, name);
626 }
627 }
628
629 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
630 if (StringTable::needs_rehashing()) {
631 const char* name = "rehashing string table";
632 EventSafepointCleanupTask event;
633 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
634 StringTable::rehash_table();
635 event_safepoint_cleanup_task_commit(event, name);
636 }
637 }
638
639 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) {
640 // CMS delays purging the CLDG until the beginning of the next safepoint and to
641 // make sure concurrent sweep is done
642 const char* name = "purging class loader data graph";
643 EventSafepointCleanupTask event;
644 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
645 ClassLoaderDataGraph::purge_if_needed();
646 event_safepoint_cleanup_task_commit(event, name);
647 }
648
649 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYSTEM_DICTIONARY_RESIZE)) {
650 const char* name = "resizing system dictionaries";
651 EventSafepointCleanupTask event;
652 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
653 ClassLoaderDataGraph::resize_if_needed();
654 event_safepoint_cleanup_task_commit(event, name);
655 }
656 _subtasks.all_tasks_completed(_num_workers);
657 }
658 };
659
660 // Various cleaning tasks that should be done periodically at safepoints.
661 void SafepointSynchronize::do_cleanup_tasks() {
662
663 TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup));
664
665 // Prepare for monitor deflation.
666 DeflateMonitorCounters deflate_counters;
667 ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
668
669 CollectedHeap* heap = Universe::heap();
670 assert(heap != NULL, "heap not initialized yet?");
671 WorkGang* cleanup_workers = heap->get_safepoint_workers();
672 if (cleanup_workers != NULL) {
673 // Parallel cleanup using GC provided thread pool.
674 uint num_cleanup_workers = cleanup_workers->active_workers();
675 ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
676 StrongRootsScope srs(num_cleanup_workers);
677 cleanup_workers->run_task(&cleanup);
678 } else {
679 // Serial cleanup using VMThread.
680 ParallelSPCleanupTask cleanup(1, &deflate_counters);
681 StrongRootsScope srs(1);
682 cleanup.work(0);
683 }
684
685 // Finish monitor deflation.
686 ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
687 }
688
689
690 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
691 switch(state) {
692 case _thread_in_native:
693 // native threads are safe if they have no java stack or have walkable stack
694 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
695
696 // blocked threads should have already have walkable stack
697 case _thread_blocked:
698 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
699 return true;
700
701 default:
702 return false;
703 }
704 }
705
706
707 // See if the thread is running inside a lazy critical native and
708 // update the thread critical count if so. Also set a suspend flag to
709 // cause the native wrapper to return into the JVM to do the unlock
710 // once the native finishes.
711 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
712 if (state == _thread_in_native &&
713 thread->has_last_Java_frame() &&
714 thread->frame_anchor()->walkable()) {
715 // This thread might be in a critical native nmethod so look at
716 // the top of the stack and increment the critical count if it
717 // is.
718 frame wrapper_frame = thread->last_frame();
719 CodeBlob* stub_cb = wrapper_frame.cb();
720 if (stub_cb != NULL &&
721 stub_cb->is_nmethod() &&
722 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
723 // A thread could potentially be in a critical native across
724 // more than one safepoint, so only update the critical state on
725 // the first one. When it returns it will perform the unlock.
726 if (!thread->do_critical_native_unlock()) {
727 #ifdef ASSERT
728 if (!thread->in_critical()) {
729 GCLocker::increment_debug_jni_lock_count();
730 }
731 #endif
732 thread->enter_critical();
733 // Make sure the native wrapper calls back on return to
734 // perform the needed critical unlock.
735 thread->set_critical_native_unlock();
736 }
737 }
738 }
739 }
740
741
742
743 // -------------------------------------------------------------------------------------------------------
744 // Implementation of Safepoint callback point
745
746 void SafepointSynchronize::block(JavaThread *thread) {
747 assert(thread != NULL, "thread must be set");
748 assert(thread->is_Java_thread(), "not a Java thread");
749
750 // Threads shouldn't block if they are in the middle of printing, but...
751 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
752
753 // Only bail from the block() call if the thread is gone from the
754 // thread list; starting to exit should still block.
755 if (thread->is_terminated()) {
756 // block current thread if we come here from native code when VM is gone
757 thread->block_if_vm_exited();
758
759 // otherwise do nothing
760 return;
761 }
762
763 JavaThreadState state = thread->thread_state();
764 thread->frame_anchor()->make_walkable(thread);
765
766 // Check that we have a valid thread_state at this point
767 switch(state) {
768 case _thread_in_vm_trans:
769 case _thread_in_Java: // From compiled code
770
771 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
772 // we pretend we are still in the VM.
773 thread->set_thread_state(_thread_in_vm);
774
775 if (is_synchronizing()) {
776 Atomic::inc (&TryingToBlock) ;
777 }
778
779 // We will always be holding the Safepoint_lock when we are examine the state
780 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
781 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
782 Safepoint_lock->lock_without_safepoint_check();
783 if (is_synchronizing()) {
784 // Decrement the number of threads to wait for and signal vm thread
785 assert(_waiting_to_block > 0, "sanity check");
786 _waiting_to_block--;
787 thread->safepoint_state()->set_has_called_back(true);
788
789 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
790 if (thread->in_critical()) {
791 // Notice that this thread is in a critical section
792 increment_jni_active_count();
793 }
794
795 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
796 if (_waiting_to_block == 0) {
797 Safepoint_lock->notify_all();
798 }
799 }
800
801 // We transition the thread to state _thread_blocked here, but
802 // we can't do our usual check for external suspension and then
803 // self-suspend after the lock_without_safepoint_check() call
804 // below because we are often called during transitions while
805 // we hold different locks. That would leave us suspended while
806 // holding a resource which results in deadlocks.
807 thread->set_thread_state(_thread_blocked);
808 Safepoint_lock->unlock();
809
810 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
811 // the entire safepoint, the threads will all line up here during the safepoint.
812 Threads_lock->lock_without_safepoint_check();
813 // restore original state. This is important if the thread comes from compiled code, so it
814 // will continue to execute with the _thread_in_Java state.
815 thread->set_thread_state(state);
816 Threads_lock->unlock();
817 break;
818
819 case _thread_in_native_trans:
820 case _thread_blocked_trans:
821 case _thread_new_trans:
822 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
823 thread->print_thread_state();
824 fatal("Deadlock in safepoint code. "
825 "Should have called back to the VM before blocking.");
826 }
827
828 // We transition the thread to state _thread_blocked here, but
829 // we can't do our usual check for external suspension and then
830 // self-suspend after the lock_without_safepoint_check() call
831 // below because we are often called during transitions while
832 // we hold different locks. That would leave us suspended while
833 // holding a resource which results in deadlocks.
834 thread->set_thread_state(_thread_blocked);
835
836 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
837 // the safepoint code might still be waiting for it to block. We need to change the state here,
838 // so it can see that it is at a safepoint.
839
840 // Block until the safepoint operation is completed.
841 Threads_lock->lock_without_safepoint_check();
842
843 // Restore state
844 thread->set_thread_state(state);
845
846 Threads_lock->unlock();
847 break;
848
849 default:
850 fatal("Illegal threadstate encountered: %d", state);
851 }
852
853 // Check for pending. async. exceptions or suspends - except if the
854 // thread was blocked inside the VM. has_special_runtime_exit_condition()
855 // is called last since it grabs a lock and we only want to do that when
856 // we must.
857 //
858 // Note: we never deliver an async exception at a polling point as the
859 // compiler may not have an exception handler for it. The polling
860 // code will notice the async and deoptimize and the exception will
861 // be delivered. (Polling at a return point is ok though). Sure is
862 // a lot of bother for a deprecated feature...
863 //
864 // We don't deliver an async exception if the thread state is
865 // _thread_in_native_trans so JNI functions won't be called with
866 // a surprising pending exception. If the thread state is going back to java,
867 // async exception is checked in check_special_condition_for_native_trans().
868
869 if (state != _thread_blocked_trans &&
870 state != _thread_in_vm_trans &&
871 thread->has_special_runtime_exit_condition()) {
872 thread->handle_special_runtime_exit_condition(
873 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
874 }
875 }
876
877 // ------------------------------------------------------------------------------------------------------
878 // Exception handlers
879
880
881 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
882 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
883 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
884 if (!ThreadLocalHandshakes) {
885 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
886 }
887
888 if (ShowSafepointMsgs) {
889 tty->print("handle_polling_page_exception: ");
890 }
891
892 if (PrintSafepointStatistics) {
893 inc_page_trap_count();
894 }
895
896 ThreadSafepointState* state = thread->safepoint_state();
897
898 state->handle_polling_page_exception();
899 }
900
901
902 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
903 if (!timeout_error_printed) {
904 timeout_error_printed = true;
905 // Print out the thread info which didn't reach the safepoint for debugging
906 // purposes (useful when there are lots of threads in the debugger).
907 tty->cr();
908 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
909 if (reason == _spinning_timeout) {
910 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
911 } else if (reason == _blocking_timeout) {
912 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
913 }
914
915 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
916 ThreadSafepointState *cur_state;
917 ResourceMark rm;
918 for (JavaThread *cur_thread = Threads::first(); cur_thread;
919 cur_thread = cur_thread->next()) {
920 cur_state = cur_thread->safepoint_state();
921
922 if (cur_thread->thread_state() != _thread_blocked &&
923 ((reason == _spinning_timeout && cur_state->is_running()) ||
924 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
925 tty->print("# ");
926 cur_thread->print();
927 tty->cr();
928 }
929 }
930 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
931 }
932
933 // To debug the long safepoint, specify both DieOnSafepointTimeout &
934 // ShowMessageBoxOnError.
935 if (DieOnSafepointTimeout) {
936 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
937 SafepointTimeoutDelay, VMThread::vm_safepoint_description());
938 }
939 }
940
941
942 // -------------------------------------------------------------------------------------------------------
943 // Implementation of ThreadSafepointState
944
945 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
946 _thread = thread;
947 _type = _running;
948 _has_called_back = false;
949 _at_poll_safepoint = false;
950 }
951
952 void ThreadSafepointState::create(JavaThread *thread) {
953 ThreadSafepointState *state = new ThreadSafepointState(thread);
954 thread->set_safepoint_state(state);
955 }
956
957 void ThreadSafepointState::destroy(JavaThread *thread) {
958 if (thread->safepoint_state()) {
959 delete(thread->safepoint_state());
960 thread->set_safepoint_state(NULL);
961 }
962 }
963
964 void ThreadSafepointState::examine_state_of_thread() {
965 assert(is_running(), "better be running or just have hit safepoint poll");
966
967 JavaThreadState state = _thread->thread_state();
968
969 // Save the state at the start of safepoint processing.
970 _orig_thread_state = state;
971
972 // Check for a thread that is suspended. Note that thread resume tries
973 // to grab the Threads_lock which we own here, so a thread cannot be
974 // resumed during safepoint synchronization.
975
976 // We check to see if this thread is suspended without locking to
977 // avoid deadlocking with a third thread that is waiting for this
978 // thread to be suspended. The third thread can notice the safepoint
979 // that we're trying to start at the beginning of its SR_lock->wait()
980 // call. If that happens, then the third thread will block on the
981 // safepoint while still holding the underlying SR_lock. We won't be
982 // able to get the SR_lock and we'll deadlock.
983 //
984 // We don't need to grab the SR_lock here for two reasons:
985 // 1) The suspend flags are both volatile and are set with an
986 // Atomic::cmpxchg() call so we should see the suspended
987 // state right away.
988 // 2) We're being called from the safepoint polling loop; if
989 // we don't see the suspended state on this iteration, then
990 // we'll come around again.
991 //
992 bool is_suspended = _thread->is_ext_suspended();
993 if (is_suspended) {
994 roll_forward(_at_safepoint);
995 return;
996 }
997
998 // Some JavaThread states have an initial safepoint state of
999 // running, but are actually at a safepoint. We will happily
1000 // agree and update the safepoint state here.
1001 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
1002 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
1003 roll_forward(_at_safepoint);
1004 return;
1005 }
1006
1007 if (state == _thread_in_vm) {
1008 roll_forward(_call_back);
1009 return;
1010 }
1011
1012 // All other thread states will continue to run until they
1013 // transition and self-block in state _blocked
1014 // Safepoint polling in compiled code causes the Java threads to do the same.
1015 // Note: new threads may require a malloc so they must be allowed to finish
1016
1017 assert(is_running(), "examine_state_of_thread on non-running thread");
1018 return;
1019 }
1020
1021 // Returns true is thread could not be rolled forward at present position.
1022 void ThreadSafepointState::roll_forward(suspend_type type) {
1023 _type = type;
1024
1025 switch(_type) {
1026 case _at_safepoint:
1027 SafepointSynchronize::signal_thread_at_safepoint();
1028 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
1029 if (_thread->in_critical()) {
1030 // Notice that this thread is in a critical section
1031 SafepointSynchronize::increment_jni_active_count();
1032 }
1033 break;
1034
1035 case _call_back:
1036 set_has_called_back(false);
1037 break;
1038
1039 case _running:
1040 default:
1041 ShouldNotReachHere();
1042 }
1043 }
1044
1045 void ThreadSafepointState::restart() {
1046 switch(type()) {
1047 case _at_safepoint:
1048 case _call_back:
1049 break;
1050
1051 case _running:
1052 default:
1053 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
1054 p2i(_thread), _type);
1055 _thread->print();
1056 ShouldNotReachHere();
1057 }
1058 _type = _running;
1059 set_has_called_back(false);
1060 }
1061
1062
1063 void ThreadSafepointState::print_on(outputStream *st) const {
1064 const char *s = NULL;
1065
1066 switch(_type) {
1067 case _running : s = "_running"; break;
1068 case _at_safepoint : s = "_at_safepoint"; break;
1069 case _call_back : s = "_call_back"; break;
1070 default:
1071 ShouldNotReachHere();
1072 }
1073
1074 st->print_cr("Thread: " INTPTR_FORMAT
1075 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1076 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
1077 _at_poll_safepoint);
1078
1079 _thread->print_thread_state_on(st);
1080 }
1081
1082 // ---------------------------------------------------------------------------------------------------------------------
1083
1084 // Block the thread at poll or poll return for safepoint/handshake.
1085 void ThreadSafepointState::handle_polling_page_exception() {
1086
1087 // Check state. block() will set thread state to thread_in_vm which will
1088 // cause the safepoint state _type to become _call_back.
1089 suspend_type t = type();
1090 assert(!SafepointMechanism::uses_global_page_poll() || t == ThreadSafepointState::_running,
1091 "polling page exception on thread not running state: %u", uint(t));
1092
1093 // Step 1: Find the nmethod from the return address
1094 if (ShowSafepointMsgs && Verbose) {
1095 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
1096 }
1097 address real_return_addr = thread()->saved_exception_pc();
1098
1099 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1100 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1101 CompiledMethod* nm = (CompiledMethod*)cb;
1102
1103 // Find frame of caller
1104 frame stub_fr = thread()->last_frame();
1105 CodeBlob* stub_cb = stub_fr.cb();
1106 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1107 RegisterMap map(thread(), true);
1108 frame caller_fr = stub_fr.sender(&map);
1109
1110 // Should only be poll_return or poll
1111 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1112
1113 // This is a poll immediately before a return. The exception handling code
1114 // has already had the effect of causing the return to occur, so the execution
1115 // will continue immediately after the call. In addition, the oopmap at the
1116 // return point does not mark the return value as an oop (if it is), so
1117 // it needs a handle here to be updated.
1118 if( nm->is_at_poll_return(real_return_addr) ) {
1119 // See if return type is an oop.
1120 bool return_oop = nm->method()->is_returning_oop();
1121 Handle return_value;
1122 if (return_oop) {
1123 // The oop result has been saved on the stack together with all
1124 // the other registers. In order to preserve it over GCs we need
1125 // to keep it in a handle.
1126 oop result = caller_fr.saved_oop_result(&map);
1127 assert(oopDesc::is_oop_or_null(result), "must be oop");
1128 return_value = Handle(thread(), result);
1129 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1130 }
1131
1132 // Block the thread
1133 SafepointMechanism::block_if_requested(thread());
1134
1135 // restore oop result, if any
1136 if (return_oop) {
1137 caller_fr.set_saved_oop_result(&map, return_value());
1138 }
1139 }
1140
1141 // This is a safepoint poll. Verify the return address and block.
1142 else {
1143 set_at_poll_safepoint(true);
1144
1145 // verify the blob built the "return address" correctly
1146 assert(real_return_addr == caller_fr.pc(), "must match");
1147
1148 // Block the thread
1149 SafepointMechanism::block_if_requested(thread());
1150 set_at_poll_safepoint(false);
1151
1152 // If we have a pending async exception deoptimize the frame
1153 // as otherwise we may never deliver it.
1154 if (thread()->has_async_condition()) {
1155 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1156 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1157 }
1158
1159 // If an exception has been installed we must check for a pending deoptimization
1160 // Deoptimize frame if exception has been thrown.
1161
1162 if (thread()->has_pending_exception() ) {
1163 RegisterMap map(thread(), true);
1164 frame caller_fr = stub_fr.sender(&map);
1165 if (caller_fr.is_deoptimized_frame()) {
1166 // The exception patch will destroy registers that are still
1167 // live and will be needed during deoptimization. Defer the
1168 // Async exception should have deferred the exception until the
1169 // next safepoint which will be detected when we get into
1170 // the interpreter so if we have an exception now things
1171 // are messed up.
1172
1173 fatal("Exception installed and deoptimization is pending");
1174 }
1175 }
1176 }
1177 }
1178
1179
1180 //
1181 // Statistics & Instrumentations
1182 //
1183 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1184 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1185 int SafepointSynchronize::_cur_stat_index = 0;
1186 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1187 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1188 jlong SafepointSynchronize::_max_sync_time = 0;
1189 jlong SafepointSynchronize::_max_vmop_time = 0;
1190 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1191
1192 static jlong cleanup_end_time = 0;
1193 static bool need_to_track_page_armed_status = false;
1194 static bool init_done = false;
1195
1196 // Helper method to print the header.
1197 static void print_header() {
1198 // The number of spaces is significant here, and should match the format
1199 // specifiers in print_statistics().
1200
1201 tty->print(" vmop "
1202 "[ threads: total initially_running wait_to_block ]"
1203 "[ time: spin block sync cleanup vmop ] ");
1204
1205 // no page armed status printed out if it is always armed.
1206 if (need_to_track_page_armed_status) {
1207 tty->print("page_armed ");
1208 }
1209
1210 tty->print_cr("page_trap_count");
1211 }
1212
1213 void SafepointSynchronize::deferred_initialize_stat() {
1214 if (init_done) return;
1215
1216 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1217 // be printed right away, in which case, _safepoint_stats will regress to
1218 // a single element array. Otherwise, it is a circular ring buffer with default
1219 // size of PrintSafepointStatisticsCount.
1220 int stats_array_size;
1221 if (PrintSafepointStatisticsTimeout > 0) {
1222 stats_array_size = 1;
1223 PrintSafepointStatistics = true;
1224 } else {
1225 stats_array_size = PrintSafepointStatisticsCount;
1226 }
1227 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1228 * sizeof(SafepointStats), mtInternal);
1229 guarantee(_safepoint_stats != NULL,
1230 "not enough memory for safepoint instrumentation data");
1231
1232 if (DeferPollingPageLoopCount >= 0) {
1233 need_to_track_page_armed_status = true;
1234 }
1235 init_done = true;
1236 }
1237
1238 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1239 assert(init_done, "safepoint statistics array hasn't been initialized");
1240 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1241
1242 spstat->_time_stamp = _ts_of_current_safepoint;
1243
1244 VM_Operation *op = VMThread::vm_operation();
1245 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1246 if (op != NULL) {
1247 _safepoint_reasons[spstat->_vmop_type]++;
1248 }
1249
1250 spstat->_nof_total_threads = nof_threads;
1251 spstat->_nof_initial_running_threads = nof_running;
1252 spstat->_nof_threads_hit_page_trap = 0;
1253
1254 // Records the start time of spinning. The real time spent on spinning
1255 // will be adjusted when spin is done. Same trick is applied for time
1256 // spent on waiting for threads to block.
1257 if (nof_running != 0) {
1258 spstat->_time_to_spin = os::javaTimeNanos();
1259 } else {
1260 spstat->_time_to_spin = 0;
1261 }
1262 }
1263
1264 void SafepointSynchronize::update_statistics_on_spin_end() {
1265 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1266
1267 jlong cur_time = os::javaTimeNanos();
1268
1269 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1270 if (spstat->_nof_initial_running_threads != 0) {
1271 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1272 }
1273
1274 if (need_to_track_page_armed_status) {
1275 spstat->_page_armed = (PageArmed == 1);
1276 }
1277
1278 // Records the start time of waiting for to block. Updated when block is done.
1279 if (_waiting_to_block != 0) {
1280 spstat->_time_to_wait_to_block = cur_time;
1281 } else {
1282 spstat->_time_to_wait_to_block = 0;
1283 }
1284 }
1285
1286 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1287 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1288
1289 if (spstat->_nof_threads_wait_to_block != 0) {
1290 spstat->_time_to_wait_to_block = end_time -
1291 spstat->_time_to_wait_to_block;
1292 }
1293
1294 // Records the end time of sync which will be used to calculate the total
1295 // vm operation time. Again, the real time spending in syncing will be deducted
1296 // from the start of the sync time later when end_statistics is called.
1297 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1298 if (spstat->_time_to_sync > _max_sync_time) {
1299 _max_sync_time = spstat->_time_to_sync;
1300 }
1301
1302 spstat->_time_to_do_cleanups = end_time;
1303 }
1304
1305 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1306 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1307
1308 // Record how long spent in cleanup tasks.
1309 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1310
1311 cleanup_end_time = end_time;
1312 }
1313
1314 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1315 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1316
1317 // Update the vm operation time.
1318 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1319 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1320 _max_vmop_time = spstat->_time_to_exec_vmop;
1321 }
1322 // Only the sync time longer than the specified
1323 // PrintSafepointStatisticsTimeout will be printed out right away.
1324 // By default, it is -1 meaning all samples will be put into the list.
1325 if ( PrintSafepointStatisticsTimeout > 0) {
1326 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1327 print_statistics();
1328 }
1329 } else {
1330 // The safepoint statistics will be printed out when the _safepoin_stats
1331 // array fills up.
1332 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1333 print_statistics();
1334 _cur_stat_index = 0;
1335 } else {
1336 _cur_stat_index++;
1337 }
1338 }
1339 }
1340
1341 void SafepointSynchronize::print_statistics() {
1342 for (int index = 0; index <= _cur_stat_index; index++) {
1343 if (index % 30 == 0) {
1344 print_header();
1345 }
1346 SafepointStats* sstats = &_safepoint_stats[index];
1347 tty->print("%8.3f: ", sstats->_time_stamp);
1348 tty->print("%-30s [ "
1349 INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " "
1350 "]",
1351 (sstats->_vmop_type == -1 ? "no vm operation" : VM_Operation::name(sstats->_vmop_type)),
1352 sstats->_nof_total_threads,
1353 sstats->_nof_initial_running_threads,
1354 sstats->_nof_threads_wait_to_block);
1355 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1356 tty->print("[ "
1357 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1358 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1359 INT64_FORMAT_W(7) " ] ",
1360 (int64_t)(sstats->_time_to_spin / MICROUNITS),
1361 (int64_t)(sstats->_time_to_wait_to_block / MICROUNITS),
1362 (int64_t)(sstats->_time_to_sync / MICROUNITS),
1363 (int64_t)(sstats->_time_to_do_cleanups / MICROUNITS),
1364 (int64_t)(sstats->_time_to_exec_vmop / MICROUNITS));
1365
1366 if (need_to_track_page_armed_status) {
1367 tty->print(INT32_FORMAT_W(10) " ", sstats->_page_armed);
1368 }
1369 tty->print_cr(INT32_FORMAT_W(15) " ", sstats->_nof_threads_hit_page_trap);
1370 }
1371 }
1372
1373 // This method will be called when VM exits. It will first call
1374 // print_statistics to print out the rest of the sampling. Then
1375 // it tries to summarize the sampling.
1376 void SafepointSynchronize::print_stat_on_exit() {
1377 if (_safepoint_stats == NULL) return;
1378
1379 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1380
1381 // During VM exit, end_statistics may not get called and in that
1382 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1383 // don't print it out.
1384 // Approximate the vm op time.
1385 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1386 os::javaTimeNanos() - cleanup_end_time;
1387
1388 if ( PrintSafepointStatisticsTimeout < 0 ||
1389 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1390 print_statistics();
1391 }
1392 tty->cr();
1393
1394 // Print out polling page sampling status.
1395 if (!need_to_track_page_armed_status) {
1396 tty->print_cr("Polling page always armed");
1397 } else {
1398 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
1399 DeferPollingPageLoopCount);
1400 }
1401
1402 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1403 if (_safepoint_reasons[index] != 0) {
1404 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1405 _safepoint_reasons[index]);
1406 }
1407 }
1408
1409 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1410 _coalesced_vmop_count);
1411 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1412 (int64_t)(_max_sync_time / MICROUNITS));
1413 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1414 INT64_FORMAT_W(5) " ms",
1415 (int64_t)(_max_vmop_time / MICROUNITS));
1416 }
1417
1418 // ------------------------------------------------------------------------------------------------
1419 // Non-product code
1420
1421 #ifndef PRODUCT
1422
1423 void SafepointSynchronize::print_state() {
1424 if (_state == _not_synchronized) {
1425 tty->print_cr("not synchronized");
1426 } else if (_state == _synchronizing || _state == _synchronized) {
1427 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1428 "synchronized");
1429
1430 for (JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1431 cur->safepoint_state()->print();
1432 }
1433 }
1434 }
1435
1436 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1437 if (ShowSafepointMsgs) {
1438 va_list ap;
1439 va_start(ap, format);
1440 tty->vprint_cr(format, ap);
1441 va_end(ap);
1442 }
1443 }
1444
1445 #endif // !PRODUCT