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/threadSMR.hpp"
63 #include "runtime/timerTrace.hpp"
64 #include "services/runtimeService.hpp"
65 #include "trace/tracing.hpp"
66 #include "trace/traceMacros.hpp"
67 #include "utilities/events.hpp"
68 #include "utilities/macros.hpp"
69 #ifdef COMPILER1
70 #include "c1/c1_globals.hpp"
71 #endif
72
73 // --------------------------------------------------------------------------------------------------
74 // Implementation of Safepoint begin/end
75
76 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
77 volatile int SafepointSynchronize::_waiting_to_block = 0;
78 volatile int SafepointSynchronize::_safepoint_counter = 0;
79 int SafepointSynchronize::_current_jni_active_count = 0;
80 long SafepointSynchronize::_end_of_last_safepoint = 0;
81 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
82 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
83 static bool timeout_error_printed = false;
84
85 // Roll all threads forward to a safepoint and suspend them all
86 void SafepointSynchronize::begin() {
87 EventSafepointBegin begin_event;
88 Thread* myThread = Thread::current();
89 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
90
91 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
92 _safepoint_begin_time = os::javaTimeNanos();
93 _ts_of_current_safepoint = tty->time_stamp().seconds();
94 }
95
96 Universe::heap()->safepoint_synchronize_begin();
97
98 // By getting the Threads_lock, we assure that no threads are about to start or
99 // exit. It is released again in SafepointSynchronize::end().
100 Threads_lock->lock();
101
102 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
103
104 int nof_threads = Threads::number_of_threads();
105
106 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads);
107
108 RuntimeService::record_safepoint_begin();
109
110 MutexLocker mu(Safepoint_lock);
111
112 // Reset the count of active JNI critical threads
113 _current_jni_active_count = 0;
114
115 // Set number of threads to wait for, before we initiate the callbacks
116 _waiting_to_block = nof_threads;
117 TryingToBlock = 0 ;
118 int still_running = nof_threads;
119
120 // Save the starting time, so that it can be compared to see if this has taken
121 // too long to complete.
122 jlong safepoint_limit_time = 0;
123 timeout_error_printed = false;
124
125 // PrintSafepointStatisticsTimeout can be specified separately. When
126 // specified, PrintSafepointStatistics will be set to true in
127 // deferred_initialize_stat method. The initialization has to be done
128 // early enough to avoid any races. See bug 6880029 for details.
129 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
130 deferred_initialize_stat();
131 }
132
133 // Begin the process of bringing the system to a safepoint.
134 // Java threads can be in several different states and are
135 // stopped by different mechanisms:
136 //
137 // 1. Running interpreted
138 // The interpreter dispatch table is changed to force it to
139 // check for a safepoint condition between bytecodes.
140 // 2. Running in native code
141 // When returning from the native code, a Java thread must check
142 // the safepoint _state to see if we must block. If the
143 // VM thread sees a Java thread in native, it does
144 // not wait for this thread to block. The order of the memory
145 // writes and reads of both the safepoint state and the Java
146 // threads state is critical. In order to guarantee that the
147 // memory writes are serialized with respect to each other,
148 // the VM thread issues a memory barrier instruction
149 // (on MP systems). In order to avoid the overhead of issuing
150 // a memory barrier for each Java thread making native calls, each Java
151 // thread performs a write to a single memory page after changing
152 // the thread state. The VM thread performs a sequence of
153 // mprotect OS calls which forces all previous writes from all
154 // Java threads to be serialized. This is done in the
155 // os::serialize_thread_states() call. This has proven to be
156 // much more efficient than executing a membar instruction
157 // on every call to native code.
158 // 3. Running compiled Code
159 // Compiled code reads a global (Safepoint Polling) page that
160 // is set to fault if we are trying to get to a safepoint.
161 // 4. Blocked
162 // A thread which is blocked will not be allowed to return from the
163 // block condition until the safepoint operation is complete.
164 // 5. In VM or Transitioning between states
165 // If a Java thread is currently running in the VM or transitioning
166 // between states, the safepointing code will wait for the thread to
167 // block itself when it attempts transitions to a new state.
168 //
169 {
170 EventSafepointStateSynchronization sync_event;
171 int initial_running = 0;
172
173 _state = _synchronizing;
174
175 if (SafepointMechanism::uses_thread_local_poll()) {
176 // Arming the per thread poll while having _state != _not_synchronized means safepointing
177 log_trace(safepoint)("Setting thread local yield flag for threads");
178 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
179 // Make sure the threads start polling, it is time to yield.
180 SafepointMechanism::arm_local_poll(cur); // release store, global state -> local state
181 }
182 }
183 OrderAccess::fence(); // storestore|storeload, global state -> local state
184
185 // Flush all thread states to memory
186 if (!UseMembar) {
187 os::serialize_thread_states();
188 }
189
190 if (SafepointMechanism::uses_global_page_poll()) {
191 // Make interpreter safepoint aware
192 Interpreter::notice_safepoints();
193
194 if (DeferPollingPageLoopCount < 0) {
195 // Make polling safepoint aware
196 guarantee (PageArmed == 0, "invariant") ;
197 PageArmed = 1 ;
198 os::make_polling_page_unreadable();
199 }
200 }
201
202 // Consider using active_processor_count() ... but that call is expensive.
203 int ncpus = os::processor_count() ;
204 unsigned int iterations = 0;
205
206 {
207 JavaThreadIteratorWithHandle jtiwh;
208 #ifdef ASSERT
209 for (; JavaThread *cur = jtiwh.next(); ) {
210 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
211 // Clear the visited flag to ensure that the critical counts are collected properly.
212 cur->set_visited_for_critical_count(false);
213 }
214 #endif // ASSERT
215
216 if (SafepointTimeout)
217 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
218
219 // Iterate through all threads until it have been determined how to stop them all at a safepoint
220 int steps = 0 ;
221 while(still_running > 0) {
222 jtiwh.rewind();
223 for (; JavaThread *cur = jtiwh.next(); ) {
224 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
225 ThreadSafepointState *cur_state = cur->safepoint_state();
226 if (cur_state->is_running()) {
227 cur_state->examine_state_of_thread();
228 if (!cur_state->is_running()) {
229 still_running--;
230 // consider adjusting steps downward:
231 // steps = 0
232 // steps -= NNN
233 // steps >>= 1
234 // steps = MIN(steps, 2000-100)
235 // if (iterations != 0) steps -= NNN
236 }
237 LogTarget(Trace, safepoint) lt;
238 if (lt.is_enabled()) {
239 ResourceMark rm;
240 LogStream ls(lt);
241 cur_state->print_on(&ls);
242 }
243 }
244 }
245
246 if (iterations == 0) {
247 initial_running = still_running;
248 if (PrintSafepointStatistics) {
249 begin_statistics(nof_threads, still_running);
250 }
251 }
252
253 if (still_running > 0) {
254 // Check for if it takes to long
255 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
256 print_safepoint_timeout(_spinning_timeout);
257 }
258
259 // Spin to avoid context switching.
260 // There's a tension between allowing the mutators to run (and rendezvous)
261 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
262 // a mutator might otherwise use profitably to reach a safepoint. Excessive
263 // spinning by the VM thread on a saturated system can increase rendezvous latency.
264 // Blocking or yielding incur their own penalties in the form of context switching
265 // and the resultant loss of $ residency.
266 //
267 // Further complicating matters is that yield() does not work as naively expected
268 // on many platforms -- yield() does not guarantee that any other ready threads
269 // will run. As such we revert to naked_short_sleep() after some number of iterations.
270 // nakes_short_sleep() is implemented as a short unconditional sleep.
271 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
272 // can actually increase the time it takes the VM thread to detect that a system-wide
273 // stop-the-world safepoint has been reached. In a pathological scenario such as that
274 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
275 // In that case the mutators will be stalled waiting for the safepoint to complete and the
276 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
277 // will eventually wake up and detect that all mutators are safe, at which point
278 // we'll again make progress.
279 //
280 // Beware too that that the VMThread typically runs at elevated priority.
281 // Its default priority is higher than the default mutator priority.
282 // Obviously, this complicates spinning.
283 //
284 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
285 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
286 //
287 // See the comments in synchronizer.cpp for additional remarks on spinning.
288 //
289 // In the future we might:
290 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
291 // This is tricky as the path used by a thread exiting the JVM (say on
292 // on JNI call-out) simply stores into its state field. The burden
293 // is placed on the VM thread, which must poll (spin).
294 // 2. Find something useful to do while spinning. If the safepoint is GC-related
295 // we might aggressively scan the stacks of threads that are already safe.
296 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
297 // If all the mutators are ONPROC there's no reason to sleep or yield.
298 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
299 // 5. Check system saturation. If the system is not fully saturated then
300 // simply spin and avoid sleep/yield.
301 // 6. As still-running mutators rendezvous they could unpark the sleeping
302 // VMthread. This works well for still-running mutators that become
303 // safe. The VMthread must still poll for mutators that call-out.
304 // 7. Drive the policy on time-since-begin instead of iterations.
305 // 8. Consider making the spin duration a function of the # of CPUs:
306 // Spin = (((ncpus-1) * M) + K) + F(still_running)
307 // Alternately, instead of counting iterations of the outer loop
308 // we could count the # of threads visited in the inner loop, above.
309 // 9. On windows consider using the return value from SwitchThreadTo()
310 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
311
312 if (SafepointMechanism::uses_global_page_poll() && int(iterations) == DeferPollingPageLoopCount) {
313 guarantee (PageArmed == 0, "invariant") ;
314 PageArmed = 1 ;
315 os::make_polling_page_unreadable();
316 }
317
318 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
319 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
320 ++steps ;
321 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
322 SpinPause() ; // MP-Polite spin
323 } else
324 if (steps < DeferThrSuspendLoopCount) {
325 os::naked_yield() ;
326 } else {
327 os::naked_short_sleep(1);
328 }
329
330 iterations ++ ;
331 }
332 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
333 }
334 } // ThreadsListHandle destroyed here.
335 assert(still_running == 0, "sanity check");
336
337 if (PrintSafepointStatistics) {
338 update_statistics_on_spin_end();
339 }
340
341 if (sync_event.should_commit()) {
342 // Group this event together with the ones committed after the counter is increased
343 sync_event.set_safepointId(safepoint_counter() + 1);
344 sync_event.set_initialThreadCount(initial_running);
345 sync_event.set_runningThreadCount(_waiting_to_block);
346 sync_event.set_iterations(iterations);
347 sync_event.commit();
348 }
349 } // EventSafepointStateSynchronization destroyed here.
350
351 // wait until all threads are stopped
352 {
353 EventSafepointWaitBlocked wait_blocked_event;
354 int initial_waiting_to_block = _waiting_to_block;
355
356 while (_waiting_to_block > 0) {
357 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
358 if (!SafepointTimeout || timeout_error_printed) {
359 Safepoint_lock->wait(true); // true, means with no safepoint checks
360 } else {
361 // Compute remaining time
362 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
363
364 // If there is no remaining time, then there is an error
365 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
366 print_safepoint_timeout(_blocking_timeout);
367 }
368 }
369 }
370 assert(_waiting_to_block == 0, "sanity check");
371
372 #ifndef PRODUCT
373 if (SafepointTimeout) {
374 jlong current_time = os::javaTimeNanos();
375 if (safepoint_limit_time < current_time) {
376 tty->print_cr("# SafepointSynchronize: Finished after "
377 INT64_FORMAT_W(6) " ms",
378 (int64_t)((current_time - safepoint_limit_time) / MICROUNITS +
379 (jlong)SafepointTimeoutDelay));
380 }
381 }
382 #endif
383
384 assert((_safepoint_counter & 0x1) == 0, "must be even");
385 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
386 _safepoint_counter ++;
387
388 // Record state
389 _state = _synchronized;
390
391 OrderAccess::fence();
392
393 if (wait_blocked_event.should_commit()) {
394 wait_blocked_event.set_safepointId(safepoint_counter());
395 wait_blocked_event.set_runningThreadCount(initial_waiting_to_block);
396 wait_blocked_event.commit();
397 }
398 } // EventSafepointWaitBlocked
399
400 #ifdef ASSERT
401 // Make sure all the threads were visited.
402 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
403 assert(cur->was_visited_for_critical_count(), "missed a thread");
404 }
405 #endif // ASSERT
406
407 // Update the count of active JNI critical regions
408 GCLocker::set_jni_lock_count(_current_jni_active_count);
409
410 if (log_is_enabled(Debug, safepoint)) {
411 log_debug(safepoint)("Entering safepoint region: %s", VMThread::vm_safepoint_description());
412 }
413
414 RuntimeService::record_safepoint_synchronized();
415 if (PrintSafepointStatistics) {
416 update_statistics_on_sync_end(os::javaTimeNanos());
417 }
418
419 // Call stuff that needs to be run when a safepoint is just about to be completed
420 {
421 EventSafepointCleanup cleanup_event;
422 do_cleanup_tasks();
423 if (cleanup_event.should_commit()) {
424 cleanup_event.set_safepointId(safepoint_counter());
425 cleanup_event.commit();
426 }
427 }
428
429 if (PrintSafepointStatistics) {
430 // Record how much time spend on the above cleanup tasks
431 update_statistics_on_cleanup_end(os::javaTimeNanos());
432 }
433 if (begin_event.should_commit()) {
434 begin_event.set_safepointId(safepoint_counter());
435 begin_event.set_totalThreadCount(nof_threads);
436 begin_event.set_jniCriticalThreadCount(_current_jni_active_count);
437 begin_event.commit();
438 }
439 }
440
441 // Wake up all threads, so they are ready to resume execution after the safepoint
442 // operation has been carried out
443 void SafepointSynchronize::end() {
444 EventSafepointEnd event;
445 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id"
446
447 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
448 assert((_safepoint_counter & 0x1) == 1, "must be odd");
449 _safepoint_counter ++;
450 // memory fence isn't required here since an odd _safepoint_counter
451 // value can do no harm and a fence is issued below anyway.
452
453 DEBUG_ONLY(Thread* myThread = Thread::current();)
454 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
455
456 if (PrintSafepointStatistics) {
457 end_statistics(os::javaTimeNanos());
458 }
459
460 {
461 JavaThreadIteratorWithHandle jtiwh;
462 #ifdef ASSERT
463 // A pending_exception cannot be installed during a safepoint. The threads
464 // may install an async exception after they come back from a safepoint into
465 // pending_exception after they unblock. But that should happen later.
466 for (; JavaThread *cur = jtiwh.next(); ) {
467 assert (!(cur->has_pending_exception() &&
468 cur->safepoint_state()->is_at_poll_safepoint()),
469 "safepoint installed a pending exception");
470 }
471 #endif // ASSERT
472
473 if (PageArmed) {
474 assert(SafepointMechanism::uses_global_page_poll(), "sanity");
475 // Make polling safepoint aware
476 os::make_polling_page_readable();
477 PageArmed = 0 ;
478 }
479
480 if (SafepointMechanism::uses_global_page_poll()) {
481 // Remove safepoint check from interpreter
482 Interpreter::ignore_safepoints();
483 }
484
485 {
486 MutexLocker mu(Safepoint_lock);
487
488 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
489
490 if (SafepointMechanism::uses_thread_local_poll()) {
491 _state = _not_synchronized;
492 OrderAccess::storestore(); // global state -> local state
493 jtiwh.rewind();
494 for (; JavaThread *current = jtiwh.next(); ) {
495 ThreadSafepointState* cur_state = current->safepoint_state();
496 cur_state->restart(); // TSS _running
497 SafepointMechanism::disarm_local_poll(current); // release store, local state -> polling page
498 }
499 log_debug(safepoint)("Leaving safepoint region");
500 } else {
501 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
502 // when they get restarted.
503 _state = _not_synchronized;
504 OrderAccess::fence();
505
506 log_debug(safepoint)("Leaving safepoint region");
507
508 // Start suspended threads
509 jtiwh.rewind();
510 for (; JavaThread *current = jtiwh.next(); ) {
511 // A problem occurring on Solaris is when attempting to restart threads
512 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
513 // to the next one (since it has been running the longest). We then have
514 // to wait for a cpu to become available before we can continue restarting
515 // threads.
516 // FIXME: This causes the performance of the VM to degrade when active and with
517 // large numbers of threads. Apparently this is due to the synchronous nature
518 // of suspending threads.
519 //
520 // TODO-FIXME: the comments above are vestigial and no longer apply.
521 // Furthermore, using solaris' schedctl in this particular context confers no benefit
522 if (VMThreadHintNoPreempt) {
523 os::hint_no_preempt();
524 }
525 ThreadSafepointState* cur_state = current->safepoint_state();
526 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
527 cur_state->restart();
528 assert(cur_state->is_running(), "safepoint state has not been reset");
529 }
530 }
531
532 RuntimeService::record_safepoint_end();
533
534 // Release threads lock, so threads can be created/destroyed again.
535 // It will also release all threads blocked in signal_thread_blocked.
536 Threads_lock->unlock();
537 }
538 } // ThreadsListHandle destroyed here.
539
540 Universe::heap()->safepoint_synchronize_end();
541 // record this time so VMThread can keep track how much time has elapsed
542 // since last safepoint.
543 _end_of_last_safepoint = os::javaTimeMillis();
544
545 if (event.should_commit()) {
546 event.set_safepointId(safepoint_id);
547 event.commit();
548 }
549 }
550
551 bool SafepointSynchronize::is_cleanup_needed() {
552 // Need a safepoint if there are many monitors to deflate.
553 if (ObjectSynchronizer::is_cleanup_needed()) return true;
554 // Need a safepoint if some inline cache buffers is non-empty
555 if (!InlineCacheBuffer::is_empty()) return true;
556 return false;
557 }
558
559 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) {
560 if (event.should_commit()) {
561 event.set_safepointId(SafepointSynchronize::safepoint_counter());
562 event.set_name(name);
563 event.commit();
564 }
565 }
566
567 class ParallelSPCleanupThreadClosure : public ThreadClosure {
568 private:
569 CodeBlobClosure* _nmethod_cl;
570 DeflateMonitorCounters* _counters;
571
572 public:
573 ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) :
574 _counters(counters),
575 _nmethod_cl(NMethodSweeper::prepare_mark_active_nmethods()) {}
576
577 void do_thread(Thread* thread) {
578 ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters);
579 if (_nmethod_cl != NULL && thread->is_Java_thread() &&
580 ! thread->is_Code_cache_sweeper_thread()) {
581 JavaThread* jt = (JavaThread*) thread;
582 jt->nmethods_do(_nmethod_cl);
583 }
584 }
585 };
586
587 class ParallelSPCleanupTask : public AbstractGangTask {
588 private:
589 SubTasksDone _subtasks;
590 ParallelSPCleanupThreadClosure _cleanup_threads_cl;
591 uint _num_workers;
592 DeflateMonitorCounters* _counters;
593 public:
594 ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
595 AbstractGangTask("Parallel Safepoint Cleanup"),
596 _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
597 _num_workers(num_workers),
598 _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)),
599 _counters(counters) {}
600
601 void work(uint worker_id) {
602 // All threads deflate monitors and mark nmethods (if necessary).
603 Threads::possibly_parallel_threads_do(true, &_cleanup_threads_cl);
604
605 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
606 const char* name = "deflating idle monitors";
607 EventSafepointCleanupTask event;
608 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
609 ObjectSynchronizer::deflate_idle_monitors(_counters);
610 event_safepoint_cleanup_task_commit(event, name);
611 }
612
613 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
614 const char* name = "updating inline caches";
615 EventSafepointCleanupTask event;
616 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
617 InlineCacheBuffer::update_inline_caches();
618 event_safepoint_cleanup_task_commit(event, name);
619 }
620
621 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
622 const char* name = "compilation policy safepoint handler";
623 EventSafepointCleanupTask event;
624 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
625 CompilationPolicy::policy()->do_safepoint_work();
626 event_safepoint_cleanup_task_commit(event, name);
627 }
628
629 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
630 if (SymbolTable::needs_rehashing()) {
631 const char* name = "rehashing symbol table";
632 EventSafepointCleanupTask event;
633 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
634 SymbolTable::rehash_table();
635 event_safepoint_cleanup_task_commit(event, name);
636 }
637 }
638
639 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
640 if (StringTable::needs_rehashing()) {
641 const char* name = "rehashing string table";
642 EventSafepointCleanupTask event;
643 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
644 StringTable::rehash_table();
645 event_safepoint_cleanup_task_commit(event, name);
646 }
647 }
648
649 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) {
650 // CMS delays purging the CLDG until the beginning of the next safepoint and to
651 // make sure concurrent sweep is done
652 const char* name = "purging class loader data graph";
653 EventSafepointCleanupTask event;
654 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
655 ClassLoaderDataGraph::purge_if_needed();
656 event_safepoint_cleanup_task_commit(event, name);
657 }
658
659 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYSTEM_DICTIONARY_RESIZE)) {
660 const char* name = "resizing system dictionaries";
661 EventSafepointCleanupTask event;
662 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
663 ClassLoaderDataGraph::resize_if_needed();
664 event_safepoint_cleanup_task_commit(event, name);
665 }
666 _subtasks.all_tasks_completed(_num_workers);
667 }
668 };
669
670 // Various cleaning tasks that should be done periodically at safepoints.
671 void SafepointSynchronize::do_cleanup_tasks() {
672
673 TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup));
674
675 // Prepare for monitor deflation.
676 DeflateMonitorCounters deflate_counters;
677 ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
678
679 CollectedHeap* heap = Universe::heap();
680 assert(heap != NULL, "heap not initialized yet?");
681 WorkGang* cleanup_workers = heap->get_safepoint_workers();
682 if (cleanup_workers != NULL) {
683 // Parallel cleanup using GC provided thread pool.
684 uint num_cleanup_workers = cleanup_workers->active_workers();
685 ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
686 StrongRootsScope srs(num_cleanup_workers);
687 cleanup_workers->run_task(&cleanup);
688 } else {
689 // Serial cleanup using VMThread.
690 ParallelSPCleanupTask cleanup(1, &deflate_counters);
691 StrongRootsScope srs(1);
692 cleanup.work(0);
693 }
694
695 // Finish monitor deflation.
696 ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
697 }
698
699
700 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
701 switch(state) {
702 case _thread_in_native:
703 // native threads are safe if they have no java stack or have walkable stack
704 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
705
706 // blocked threads should have already have walkable stack
707 case _thread_blocked:
708 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
709 return true;
710
711 default:
712 return false;
713 }
714 }
715
716
717 // See if the thread is running inside a lazy critical native and
718 // update the thread critical count if so. Also set a suspend flag to
719 // cause the native wrapper to return into the JVM to do the unlock
720 // once the native finishes.
721 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
722 if (state == _thread_in_native &&
723 thread->has_last_Java_frame() &&
724 thread->frame_anchor()->walkable()) {
725 // This thread might be in a critical native nmethod so look at
726 // the top of the stack and increment the critical count if it
727 // is.
728 frame wrapper_frame = thread->last_frame();
729 CodeBlob* stub_cb = wrapper_frame.cb();
730 if (stub_cb != NULL &&
731 stub_cb->is_nmethod() &&
732 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
733 // A thread could potentially be in a critical native across
734 // more than one safepoint, so only update the critical state on
735 // the first one. When it returns it will perform the unlock.
736 if (!thread->do_critical_native_unlock()) {
737 #ifdef ASSERT
738 if (!thread->in_critical()) {
739 GCLocker::increment_debug_jni_lock_count();
740 }
741 #endif
742 thread->enter_critical();
743 // Make sure the native wrapper calls back on return to
744 // perform the needed critical unlock.
745 thread->set_critical_native_unlock();
746 }
747 }
748 }
749 }
750
751
752
753 // -------------------------------------------------------------------------------------------------------
754 // Implementation of Safepoint callback point
755
756 void SafepointSynchronize::block(JavaThread *thread) {
757 assert(thread != NULL, "thread must be set");
758 assert(thread->is_Java_thread(), "not a Java thread");
759
760 // Threads shouldn't block if they are in the middle of printing, but...
761 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
762
763 // Only bail from the block() call if the thread is gone from the
764 // thread list; starting to exit should still block.
765 if (thread->is_terminated()) {
766 // block current thread if we come here from native code when VM is gone
767 thread->block_if_vm_exited();
768
769 // otherwise do nothing
770 return;
771 }
772
773 JavaThreadState state = thread->thread_state();
774 thread->frame_anchor()->make_walkable(thread);
775
776 // Check that we have a valid thread_state at this point
777 switch(state) {
778 case _thread_in_vm_trans:
779 case _thread_in_Java: // From compiled code
780
781 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
782 // we pretend we are still in the VM.
783 thread->set_thread_state(_thread_in_vm);
784
785 if (is_synchronizing()) {
786 Atomic::inc (&TryingToBlock) ;
787 }
788
789 // We will always be holding the Safepoint_lock when we are examine the state
790 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
791 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
792 Safepoint_lock->lock_without_safepoint_check();
793 if (is_synchronizing()) {
794 // Decrement the number of threads to wait for and signal vm thread
795 assert(_waiting_to_block > 0, "sanity check");
796 _waiting_to_block--;
797 thread->safepoint_state()->set_has_called_back(true);
798
799 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
800 if (thread->in_critical()) {
801 // Notice that this thread is in a critical section
802 increment_jni_active_count();
803 }
804
805 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
806 if (_waiting_to_block == 0) {
807 Safepoint_lock->notify_all();
808 }
809 }
810
811 // We transition the thread to state _thread_blocked here, but
812 // we can't do our usual check for external suspension and then
813 // self-suspend after the lock_without_safepoint_check() call
814 // below because we are often called during transitions while
815 // we hold different locks. That would leave us suspended while
816 // holding a resource which results in deadlocks.
817 thread->set_thread_state(_thread_blocked);
818 Safepoint_lock->unlock();
819
820 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
821 // the entire safepoint, the threads will all line up here during the safepoint.
822 Threads_lock->lock_without_safepoint_check();
823 // restore original state. This is important if the thread comes from compiled code, so it
824 // will continue to execute with the _thread_in_Java state.
825 thread->set_thread_state(state);
826 Threads_lock->unlock();
827 break;
828
829 case _thread_in_native_trans:
830 case _thread_blocked_trans:
831 case _thread_new_trans:
832 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
833 thread->print_thread_state();
834 fatal("Deadlock in safepoint code. "
835 "Should have called back to the VM before blocking.");
836 }
837
838 // We transition the thread to state _thread_blocked here, but
839 // we can't do our usual check for external suspension and then
840 // self-suspend after the lock_without_safepoint_check() call
841 // below because we are often called during transitions while
842 // we hold different locks. That would leave us suspended while
843 // holding a resource which results in deadlocks.
844 thread->set_thread_state(_thread_blocked);
845
846 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
847 // the safepoint code might still be waiting for it to block. We need to change the state here,
848 // so it can see that it is at a safepoint.
849
850 // Block until the safepoint operation is completed.
851 Threads_lock->lock_without_safepoint_check();
852
853 // Restore state
854 thread->set_thread_state(state);
855
856 Threads_lock->unlock();
857 break;
858
859 default:
860 fatal("Illegal threadstate encountered: %d", state);
861 }
862
863 // Check for pending. async. exceptions or suspends - except if the
864 // thread was blocked inside the VM. has_special_runtime_exit_condition()
865 // is called last since it grabs a lock and we only want to do that when
866 // we must.
867 //
868 // Note: we never deliver an async exception at a polling point as the
869 // compiler may not have an exception handler for it. The polling
870 // code will notice the async and deoptimize and the exception will
871 // be delivered. (Polling at a return point is ok though). Sure is
872 // a lot of bother for a deprecated feature...
873 //
874 // We don't deliver an async exception if the thread state is
875 // _thread_in_native_trans so JNI functions won't be called with
876 // a surprising pending exception. If the thread state is going back to java,
877 // async exception is checked in check_special_condition_for_native_trans().
878
879 if (state != _thread_blocked_trans &&
880 state != _thread_in_vm_trans &&
881 thread->has_special_runtime_exit_condition()) {
882 thread->handle_special_runtime_exit_condition(
883 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
884 }
885 }
886
887 // ------------------------------------------------------------------------------------------------------
888 // Exception handlers
889
890
891 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
892 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
893 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
894 if (!ThreadLocalHandshakes) {
895 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
896 }
897
898 if (ShowSafepointMsgs) {
899 tty->print("handle_polling_page_exception: ");
900 }
901
902 if (PrintSafepointStatistics) {
903 inc_page_trap_count();
904 }
905
906 ThreadSafepointState* state = thread->safepoint_state();
907
908 state->handle_polling_page_exception();
909 }
910
911
912 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
913 if (!timeout_error_printed) {
914 timeout_error_printed = true;
915 // Print out the thread info which didn't reach the safepoint for debugging
916 // purposes (useful when there are lots of threads in the debugger).
917 tty->cr();
918 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
919 if (reason == _spinning_timeout) {
920 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
921 } else if (reason == _blocking_timeout) {
922 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
923 }
924
925 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
926 ThreadSafepointState *cur_state;
927 ResourceMark rm;
928 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) {
929 cur_state = cur_thread->safepoint_state();
930
931 if (cur_thread->thread_state() != _thread_blocked &&
932 ((reason == _spinning_timeout && cur_state->is_running()) ||
933 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
934 tty->print("# ");
935 cur_thread->print();
936 tty->cr();
937 }
938 }
939 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
940 }
941
942 // To debug the long safepoint, specify both DieOnSafepointTimeout &
943 // ShowMessageBoxOnError.
944 if (DieOnSafepointTimeout) {
945 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
946 SafepointTimeoutDelay, VMThread::vm_safepoint_description());
947 }
948 }
949
950
951 // -------------------------------------------------------------------------------------------------------
952 // Implementation of ThreadSafepointState
953
954 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
955 _thread = thread;
956 _type = _running;
957 _has_called_back = false;
958 _at_poll_safepoint = false;
959 }
960
961 void ThreadSafepointState::create(JavaThread *thread) {
962 ThreadSafepointState *state = new ThreadSafepointState(thread);
963 thread->set_safepoint_state(state);
964 }
965
966 void ThreadSafepointState::destroy(JavaThread *thread) {
967 if (thread->safepoint_state()) {
968 delete(thread->safepoint_state());
969 thread->set_safepoint_state(NULL);
970 }
971 }
972
973 void ThreadSafepointState::examine_state_of_thread() {
974 assert(is_running(), "better be running or just have hit safepoint poll");
975
976 JavaThreadState state = _thread->thread_state();
977
978 // Save the state at the start of safepoint processing.
979 _orig_thread_state = state;
980
981 // Check for a thread that is suspended. Note that thread resume tries
982 // to grab the Threads_lock which we own here, so a thread cannot be
983 // resumed during safepoint synchronization.
984
985 // We check to see if this thread is suspended without locking to
986 // avoid deadlocking with a third thread that is waiting for this
987 // thread to be suspended. The third thread can notice the safepoint
988 // that we're trying to start at the beginning of its SR_lock->wait()
989 // call. If that happens, then the third thread will block on the
990 // safepoint while still holding the underlying SR_lock. We won't be
991 // able to get the SR_lock and we'll deadlock.
992 //
993 // We don't need to grab the SR_lock here for two reasons:
994 // 1) The suspend flags are both volatile and are set with an
995 // Atomic::cmpxchg() call so we should see the suspended
996 // state right away.
997 // 2) We're being called from the safepoint polling loop; if
998 // we don't see the suspended state on this iteration, then
999 // we'll come around again.
1000 //
1001 bool is_suspended = _thread->is_ext_suspended();
1002 if (is_suspended) {
1003 roll_forward(_at_safepoint);
1004 return;
1005 }
1006
1007 // Some JavaThread states have an initial safepoint state of
1008 // running, but are actually at a safepoint. We will happily
1009 // agree and update the safepoint state here.
1010 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
1011 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
1012 roll_forward(_at_safepoint);
1013 return;
1014 }
1015
1016 if (state == _thread_in_vm) {
1017 roll_forward(_call_back);
1018 return;
1019 }
1020
1021 // All other thread states will continue to run until they
1022 // transition and self-block in state _blocked
1023 // Safepoint polling in compiled code causes the Java threads to do the same.
1024 // Note: new threads may require a malloc so they must be allowed to finish
1025
1026 assert(is_running(), "examine_state_of_thread on non-running thread");
1027 return;
1028 }
1029
1030 // Returns true is thread could not be rolled forward at present position.
1031 void ThreadSafepointState::roll_forward(suspend_type type) {
1032 _type = type;
1033
1034 switch(_type) {
1035 case _at_safepoint:
1036 SafepointSynchronize::signal_thread_at_safepoint();
1037 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
1038 if (_thread->in_critical()) {
1039 // Notice that this thread is in a critical section
1040 SafepointSynchronize::increment_jni_active_count();
1041 }
1042 break;
1043
1044 case _call_back:
1045 set_has_called_back(false);
1046 break;
1047
1048 case _running:
1049 default:
1050 ShouldNotReachHere();
1051 }
1052 }
1053
1054 void ThreadSafepointState::restart() {
1055 switch(type()) {
1056 case _at_safepoint:
1057 case _call_back:
1058 break;
1059
1060 case _running:
1061 default:
1062 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
1063 p2i(_thread), _type);
1064 _thread->print();
1065 ShouldNotReachHere();
1066 }
1067 _type = _running;
1068 set_has_called_back(false);
1069 }
1070
1071
1072 void ThreadSafepointState::print_on(outputStream *st) const {
1073 const char *s = NULL;
1074
1075 switch(_type) {
1076 case _running : s = "_running"; break;
1077 case _at_safepoint : s = "_at_safepoint"; break;
1078 case _call_back : s = "_call_back"; break;
1079 default:
1080 ShouldNotReachHere();
1081 }
1082
1083 st->print_cr("Thread: " INTPTR_FORMAT
1084 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1085 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
1086 _at_poll_safepoint);
1087
1088 _thread->print_thread_state_on(st);
1089 }
1090
1091 // ---------------------------------------------------------------------------------------------------------------------
1092
1093 // Block the thread at poll or poll return for safepoint/handshake.
1094 void ThreadSafepointState::handle_polling_page_exception() {
1095
1096 // Check state. block() will set thread state to thread_in_vm which will
1097 // cause the safepoint state _type to become _call_back.
1098 suspend_type t = type();
1099 assert(!SafepointMechanism::uses_global_page_poll() || t == ThreadSafepointState::_running,
1100 "polling page exception on thread not running state: %u", uint(t));
1101
1102 // Step 1: Find the nmethod from the return address
1103 if (ShowSafepointMsgs && Verbose) {
1104 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
1105 }
1106 address real_return_addr = thread()->saved_exception_pc();
1107
1108 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1109 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1110 CompiledMethod* nm = (CompiledMethod*)cb;
1111
1112 // Find frame of caller
1113 frame stub_fr = thread()->last_frame();
1114 CodeBlob* stub_cb = stub_fr.cb();
1115 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1116 RegisterMap map(thread(), true);
1117 frame caller_fr = stub_fr.sender(&map);
1118
1119 // Should only be poll_return or poll
1120 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1121
1122 // This is a poll immediately before a return. The exception handling code
1123 // has already had the effect of causing the return to occur, so the execution
1124 // will continue immediately after the call. In addition, the oopmap at the
1125 // return point does not mark the return value as an oop (if it is), so
1126 // it needs a handle here to be updated.
1127 if( nm->is_at_poll_return(real_return_addr) ) {
1128 // See if return type is an oop.
1129 bool return_oop = nm->method()->is_returning_oop();
1130 Handle return_value;
1131 if (return_oop) {
1132 // The oop result has been saved on the stack together with all
1133 // the other registers. In order to preserve it over GCs we need
1134 // to keep it in a handle.
1135 oop result = caller_fr.saved_oop_result(&map);
1136 assert(oopDesc::is_oop_or_null(result), "must be oop");
1137 return_value = Handle(thread(), result);
1138 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1139 }
1140
1141 // Block the thread
1142 SafepointMechanism::block_if_requested(thread());
1143
1144 // restore oop result, if any
1145 if (return_oop) {
1146 caller_fr.set_saved_oop_result(&map, return_value());
1147 }
1148 }
1149
1150 // This is a safepoint poll. Verify the return address and block.
1151 else {
1152 set_at_poll_safepoint(true);
1153
1154 // verify the blob built the "return address" correctly
1155 assert(real_return_addr == caller_fr.pc(), "must match");
1156
1157 // Block the thread
1158 SafepointMechanism::block_if_requested(thread());
1159 set_at_poll_safepoint(false);
1160
1161 // If we have a pending async exception deoptimize the frame
1162 // as otherwise we may never deliver it.
1163 if (thread()->has_async_condition()) {
1164 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1165 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1166 }
1167
1168 // If an exception has been installed we must check for a pending deoptimization
1169 // Deoptimize frame if exception has been thrown.
1170
1171 if (thread()->has_pending_exception() ) {
1172 RegisterMap map(thread(), true);
1173 frame caller_fr = stub_fr.sender(&map);
1174 if (caller_fr.is_deoptimized_frame()) {
1175 // The exception patch will destroy registers that are still
1176 // live and will be needed during deoptimization. Defer the
1177 // Async exception should have deferred the exception until the
1178 // next safepoint which will be detected when we get into
1179 // the interpreter so if we have an exception now things
1180 // are messed up.
1181
1182 fatal("Exception installed and deoptimization is pending");
1183 }
1184 }
1185 }
1186 }
1187
1188
1189 //
1190 // Statistics & Instrumentations
1191 //
1192 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1193 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1194 int SafepointSynchronize::_cur_stat_index = 0;
1195 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1196 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1197 jlong SafepointSynchronize::_max_sync_time = 0;
1198 jlong SafepointSynchronize::_max_vmop_time = 0;
1199 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1200
1201 static jlong cleanup_end_time = 0;
1202 static bool need_to_track_page_armed_status = false;
1203 static bool init_done = false;
1204
1205 // Helper method to print the header.
1206 static void print_header() {
1207 // The number of spaces is significant here, and should match the format
1208 // specifiers in print_statistics().
1209
1210 tty->print(" vmop "
1211 "[ threads: total initially_running wait_to_block ]"
1212 "[ time: spin block sync cleanup vmop ] ");
1213
1214 // no page armed status printed out if it is always armed.
1215 if (need_to_track_page_armed_status) {
1216 tty->print("page_armed ");
1217 }
1218
1219 tty->print_cr("page_trap_count");
1220 }
1221
1222 void SafepointSynchronize::deferred_initialize_stat() {
1223 if (init_done) return;
1224
1225 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1226 // be printed right away, in which case, _safepoint_stats will regress to
1227 // a single element array. Otherwise, it is a circular ring buffer with default
1228 // size of PrintSafepointStatisticsCount.
1229 int stats_array_size;
1230 if (PrintSafepointStatisticsTimeout > 0) {
1231 stats_array_size = 1;
1232 PrintSafepointStatistics = true;
1233 } else {
1234 stats_array_size = PrintSafepointStatisticsCount;
1235 }
1236 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1237 * sizeof(SafepointStats), mtInternal);
1238 guarantee(_safepoint_stats != NULL,
1239 "not enough memory for safepoint instrumentation data");
1240
1241 if (DeferPollingPageLoopCount >= 0) {
1242 need_to_track_page_armed_status = true;
1243 }
1244 init_done = true;
1245 }
1246
1247 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1248 assert(init_done, "safepoint statistics array hasn't been initialized");
1249 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1250
1251 spstat->_time_stamp = _ts_of_current_safepoint;
1252
1253 VM_Operation *op = VMThread::vm_operation();
1254 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1255 if (op != NULL) {
1256 _safepoint_reasons[spstat->_vmop_type]++;
1257 }
1258
1259 spstat->_nof_total_threads = nof_threads;
1260 spstat->_nof_initial_running_threads = nof_running;
1261 spstat->_nof_threads_hit_page_trap = 0;
1262
1263 // Records the start time of spinning. The real time spent on spinning
1264 // will be adjusted when spin is done. Same trick is applied for time
1265 // spent on waiting for threads to block.
1266 if (nof_running != 0) {
1267 spstat->_time_to_spin = os::javaTimeNanos();
1268 } else {
1269 spstat->_time_to_spin = 0;
1270 }
1271 }
1272
1273 void SafepointSynchronize::update_statistics_on_spin_end() {
1274 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1275
1276 jlong cur_time = os::javaTimeNanos();
1277
1278 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1279 if (spstat->_nof_initial_running_threads != 0) {
1280 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1281 }
1282
1283 if (need_to_track_page_armed_status) {
1284 spstat->_page_armed = (PageArmed == 1);
1285 }
1286
1287 // Records the start time of waiting for to block. Updated when block is done.
1288 if (_waiting_to_block != 0) {
1289 spstat->_time_to_wait_to_block = cur_time;
1290 } else {
1291 spstat->_time_to_wait_to_block = 0;
1292 }
1293 }
1294
1295 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1296 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1297
1298 if (spstat->_nof_threads_wait_to_block != 0) {
1299 spstat->_time_to_wait_to_block = end_time -
1300 spstat->_time_to_wait_to_block;
1301 }
1302
1303 // Records the end time of sync which will be used to calculate the total
1304 // vm operation time. Again, the real time spending in syncing will be deducted
1305 // from the start of the sync time later when end_statistics is called.
1306 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1307 if (spstat->_time_to_sync > _max_sync_time) {
1308 _max_sync_time = spstat->_time_to_sync;
1309 }
1310
1311 spstat->_time_to_do_cleanups = end_time;
1312 }
1313
1314 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1315 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1316
1317 // Record how long spent in cleanup tasks.
1318 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1319
1320 cleanup_end_time = end_time;
1321 }
1322
1323 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1324 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1325
1326 // Update the vm operation time.
1327 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1328 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1329 _max_vmop_time = spstat->_time_to_exec_vmop;
1330 }
1331 // Only the sync time longer than the specified
1332 // PrintSafepointStatisticsTimeout will be printed out right away.
1333 // By default, it is -1 meaning all samples will be put into the list.
1334 if ( PrintSafepointStatisticsTimeout > 0) {
1335 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1336 print_statistics();
1337 }
1338 } else {
1339 // The safepoint statistics will be printed out when the _safepoin_stats
1340 // array fills up.
1341 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1342 print_statistics();
1343 _cur_stat_index = 0;
1344 } else {
1345 _cur_stat_index++;
1346 }
1347 }
1348 }
1349
1350 void SafepointSynchronize::print_statistics() {
1351 for (int index = 0; index <= _cur_stat_index; index++) {
1352 if (index % 30 == 0) {
1353 print_header();
1354 }
1355 SafepointStats* sstats = &_safepoint_stats[index];
1356 tty->print("%8.3f: ", sstats->_time_stamp);
1357 tty->print("%-30s [ "
1358 INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " "
1359 "]",
1360 (sstats->_vmop_type == -1 ? "no vm operation" : VM_Operation::name(sstats->_vmop_type)),
1361 sstats->_nof_total_threads,
1362 sstats->_nof_initial_running_threads,
1363 sstats->_nof_threads_wait_to_block);
1364 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1365 tty->print("[ "
1366 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1367 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1368 INT64_FORMAT_W(7) " ] ",
1369 (int64_t)(sstats->_time_to_spin / MICROUNITS),
1370 (int64_t)(sstats->_time_to_wait_to_block / MICROUNITS),
1371 (int64_t)(sstats->_time_to_sync / MICROUNITS),
1372 (int64_t)(sstats->_time_to_do_cleanups / MICROUNITS),
1373 (int64_t)(sstats->_time_to_exec_vmop / MICROUNITS));
1374
1375 if (need_to_track_page_armed_status) {
1376 tty->print(INT32_FORMAT_W(10) " ", sstats->_page_armed);
1377 }
1378 tty->print_cr(INT32_FORMAT_W(15) " ", sstats->_nof_threads_hit_page_trap);
1379 }
1380 }
1381
1382 // This method will be called when VM exits. It will first call
1383 // print_statistics to print out the rest of the sampling. Then
1384 // it tries to summarize the sampling.
1385 void SafepointSynchronize::print_stat_on_exit() {
1386 if (_safepoint_stats == NULL) return;
1387
1388 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1389
1390 // During VM exit, end_statistics may not get called and in that
1391 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1392 // don't print it out.
1393 // Approximate the vm op time.
1394 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1395 os::javaTimeNanos() - cleanup_end_time;
1396
1397 if ( PrintSafepointStatisticsTimeout < 0 ||
1398 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1399 print_statistics();
1400 }
1401 tty->cr();
1402
1403 // Print out polling page sampling status.
1404 if (!need_to_track_page_armed_status) {
1405 tty->print_cr("Polling page always armed");
1406 } else {
1407 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
1408 DeferPollingPageLoopCount);
1409 }
1410
1411 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1412 if (_safepoint_reasons[index] != 0) {
1413 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1414 _safepoint_reasons[index]);
1415 }
1416 }
1417
1418 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1419 _coalesced_vmop_count);
1420 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1421 (int64_t)(_max_sync_time / MICROUNITS));
1422 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1423 INT64_FORMAT_W(5) " ms",
1424 (int64_t)(_max_vmop_time / MICROUNITS));
1425 }
1426
1427 // ------------------------------------------------------------------------------------------------
1428 // Non-product code
1429
1430 #ifndef PRODUCT
1431
1432 void SafepointSynchronize::print_state() {
1433 if (_state == _not_synchronized) {
1434 tty->print_cr("not synchronized");
1435 } else if (_state == _synchronizing || _state == _synchronized) {
1436 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1437 "synchronized");
1438
1439 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
1440 cur->safepoint_state()->print();
1441 }
1442 }
1443 }
1444
1445 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1446 if (ShowSafepointMsgs) {
1447 va_list ap;
1448 va_start(ap, format);
1449 tty->vprint_cr(format, ap);
1450 va_end(ap);
1451 }
1452 }
1453
1454 #endif // !PRODUCT