1 /*
2 * Copyright (c) 1997, 2015, 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/symbolTable.hpp"
27 #include "classfile/systemDictionary.hpp"
28 #include "code/codeCache.hpp"
29 #include "code/icBuffer.hpp"
30 #include "code/nmethod.hpp"
31 #include "code/pcDesc.hpp"
32 #include "code/scopeDesc.hpp"
33 #include "gc_interface/collectedHeap.hpp"
34 #include "interpreter/interpreter.hpp"
35 #include "jfr/jfrEvents.hpp"
36 #include "memory/resourceArea.hpp"
37 #include "memory/universe.inline.hpp"
38 #include "oops/oop.inline.hpp"
39 #include "oops/symbol.hpp"
40 #include "runtime/compilationPolicy.hpp"
41 #include "runtime/deoptimization.hpp"
42 #include "runtime/frame.inline.hpp"
43 #include "runtime/interfaceSupport.hpp"
44 #include "runtime/mutexLocker.hpp"
45 #include "runtime/orderAccess.inline.hpp"
46 #include "runtime/osThread.hpp"
47 #include "runtime/safepoint.hpp"
48 #include "runtime/signature.hpp"
49 #include "runtime/stubCodeGenerator.hpp"
50 #include "runtime/stubRoutines.hpp"
51 #include "runtime/sweeper.hpp"
52 #include "runtime/synchronizer.hpp"
53 #include "runtime/thread.inline.hpp"
54 #include "services/runtimeService.hpp"
55 #include "utilities/events.hpp"
56 #include "utilities/macros.hpp"
57 #ifdef TARGET_ARCH_x86
58 # include "nativeInst_x86.hpp"
59 # include "vmreg_x86.inline.hpp"
60 #endif
61 #ifdef TARGET_ARCH_aarch64
62 # include "nativeInst_aarch64.hpp"
63 # include "vmreg_aarch64.inline.hpp"
64 #endif
65 #ifdef TARGET_ARCH_sparc
66 # include "nativeInst_sparc.hpp"
67 # include "vmreg_sparc.inline.hpp"
68 #endif
69 #ifdef TARGET_ARCH_zero
70 # include "nativeInst_zero.hpp"
71 # include "vmreg_zero.inline.hpp"
72 #endif
73 #ifdef TARGET_ARCH_arm
74 # include "nativeInst_arm.hpp"
75 # include "vmreg_arm.inline.hpp"
76 #endif
77 #ifdef TARGET_ARCH_ppc
78 # include "nativeInst_ppc.hpp"
79 # include "vmreg_ppc.inline.hpp"
80 #endif
81 #if INCLUDE_ALL_GCS
82 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
83 #include "gc_implementation/shared/suspendibleThreadSet.hpp"
84 #endif // INCLUDE_ALL_GCS
85 #ifdef COMPILER1
86 #include "c1/c1_globals.hpp"
87 #endif
88
89 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
90
91 template <typename E>
92 static void set_current_safepoint_id(E* event, int adjustment = 0) {
93 assert(event != NULL, "invariant");
94 event->set_safepointId(SafepointSynchronize::safepoint_counter() + adjustment);
95 }
96
97 static void post_safepoint_begin_event(EventSafepointBegin* event,
98 int thread_count,
99 int critical_thread_count) {
100 assert(event != NULL, "invariant");
101 assert(event->should_commit(), "invariant");
102 set_current_safepoint_id(event);
103 event->set_totalThreadCount(thread_count);
104 event->set_jniCriticalThreadCount(critical_thread_count);
105 event->commit();
106 }
107
108 static void post_safepoint_cleanup_event(EventSafepointCleanup* event) {
109 assert(event != NULL, "invariant");
110 assert(event->should_commit(), "invariant");
111 set_current_safepoint_id(event);
112 event->commit();
113 }
114
115 static void post_safepoint_synchronize_event(EventSafepointStateSynchronization* event,
116 int initial_number_of_threads,
117 int threads_waiting_to_block,
118 unsigned int iterations) {
119 assert(event != NULL, "invariant");
120 if (event->should_commit()) {
121 // Group this event together with the ones committed after the counter is increased
122 set_current_safepoint_id(event, 1);
123 event->set_initialThreadCount(initial_number_of_threads);
124 event->set_runningThreadCount(threads_waiting_to_block);
125 event->set_iterations(iterations);
126 event->commit();
127 }
128 }
129
130 static void post_safepoint_wait_blocked_event(EventSafepointWaitBlocked* event,
131 int initial_threads_waiting_to_block) {
132 assert(event != NULL, "invariant");
133 assert(event->should_commit(), "invariant");
134 set_current_safepoint_id(event);
135 event->set_runningThreadCount(initial_threads_waiting_to_block);
136 event->commit();
137 }
138
139 static void post_safepoint_cleanup_task_event(EventSafepointCleanupTask* event,
140 const char* name) {
141 assert(event != NULL, "invariant");
142 if (event->should_commit()) {
143 set_current_safepoint_id(event);
144 event->set_name(name);
145 event->commit();
146 }
147 }
148
149 static void post_safepoint_end_event(EventSafepointEnd* event) {
150 assert(event != NULL, "invariant");
151 if (event->should_commit()) {
152 // Group this event together with the ones committed before the counter increased
153 set_current_safepoint_id(event, -1);
154 event->commit();
155 }
156 }
157
158 // --------------------------------------------------------------------------------------------------
159 // Implementation of Safepoint begin/end
160
161 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
162 volatile int SafepointSynchronize::_waiting_to_block = 0;
163 volatile int SafepointSynchronize::_safepoint_counter = 0;
164 int SafepointSynchronize::_current_jni_active_count = 0;
165 long SafepointSynchronize::_end_of_last_safepoint = 0;
166 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
167 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
168 static bool timeout_error_printed = false;
169
170 // Roll all threads forward to a safepoint and suspend them all
171 void SafepointSynchronize::begin() {
172 EventSafepointBegin begin_event;
173 Thread* myThread = Thread::current();
174 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
175
176 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
177 _safepoint_begin_time = os::javaTimeNanos();
178 _ts_of_current_safepoint = tty->time_stamp().seconds();
179 }
180
181 #if INCLUDE_ALL_GCS
182 if (UseConcMarkSweepGC) {
183 // In the future we should investigate whether CMS can use the
184 // more-general mechanism below. DLD (01/05).
185 ConcurrentMarkSweepThread::synchronize(false);
186 } else if (UseG1GC || (UseShenandoahGC && UseStringDeduplication)) {
187 SuspendibleThreadSet::synchronize();
188 }
189 #endif // INCLUDE_ALL_GCS
190
191 // By getting the Threads_lock, we assure that no threads are about to start or
192 // exit. It is released again in SafepointSynchronize::end().
193 Threads_lock->lock();
194
195 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
196
197 int nof_threads = Threads::number_of_threads();
198
199 if (TraceSafepoint) {
200 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
201 }
202
203 RuntimeService::record_safepoint_begin();
204
205 MutexLocker mu(Safepoint_lock);
206
207 // Reset the count of active JNI critical threads
208 _current_jni_active_count = 0;
209
210 // Set number of threads to wait for, before we initiate the callbacks
211 _waiting_to_block = nof_threads;
212 TryingToBlock = 0 ;
213 int still_running = nof_threads;
214
215 // Save the starting time, so that it can be compared to see if this has taken
216 // too long to complete.
217 jlong safepoint_limit_time = 0;
218 timeout_error_printed = false;
219
220 // PrintSafepointStatisticsTimeout can be specified separately. When
221 // specified, PrintSafepointStatistics will be set to true in
222 // deferred_initialize_stat method. The initialization has to be done
223 // early enough to avoid any races. See bug 6880029 for details.
224 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
225 deferred_initialize_stat();
226 }
227
228 // Begin the process of bringing the system to a safepoint.
229 // Java threads can be in several different states and are
230 // stopped by different mechanisms:
231 //
232 // 1. Running interpreted
233 // The interpeter dispatch table is changed to force it to
234 // check for a safepoint condition between bytecodes.
235 // 2. Running in native code
236 // When returning from the native code, a Java thread must check
237 // the safepoint _state to see if we must block. If the
238 // VM thread sees a Java thread in native, it does
239 // not wait for this thread to block. The order of the memory
240 // writes and reads of both the safepoint state and the Java
241 // threads state is critical. In order to guarantee that the
242 // memory writes are serialized with respect to each other,
243 // the VM thread issues a memory barrier instruction
244 // (on MP systems). In order to avoid the overhead of issuing
245 // a memory barrier for each Java thread making native calls, each Java
246 // thread performs a write to a single memory page after changing
247 // the thread state. The VM thread performs a sequence of
248 // mprotect OS calls which forces all previous writes from all
249 // Java threads to be serialized. This is done in the
250 // os::serialize_thread_states() call. This has proven to be
251 // much more efficient than executing a membar instruction
252 // on every call to native code.
253 // 3. Running compiled Code
254 // Compiled code reads a global (Safepoint Polling) page that
255 // is set to fault if we are trying to get to a safepoint.
256 // 4. Blocked
257 // A thread which is blocked will not be allowed to return from the
258 // block condition until the safepoint operation is complete.
259 // 5. In VM or Transitioning between states
260 // If a Java thread is currently running in the VM or transitioning
261 // between states, the safepointing code will wait for the thread to
262 // block itself when it attempts transitions to a new state.
263 //
264 EventSafepointStateSynchronization sync_event;
265 int initial_running = 0;
266
267 _state = _synchronizing;
268 OrderAccess::fence();
269
270 // Flush all thread states to memory
271 if (!UseMembar) {
272 os::serialize_thread_states();
273 }
274
275 // Make interpreter safepoint aware
276 Interpreter::notice_safepoints();
277
278 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
279 // Make polling safepoint aware
280 guarantee (PageArmed == 0, "invariant") ;
281 PageArmed = 1 ;
282 os::make_polling_page_unreadable();
283 }
284
285 // Consider using active_processor_count() ... but that call is expensive.
286 int ncpus = os::processor_count() ;
287
288 #ifdef ASSERT
289 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
290 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
291 // Clear the visited flag to ensure that the critical counts are collected properly.
292 cur->set_visited_for_critical_count(false);
293 }
294 #endif // ASSERT
295
296 if (SafepointTimeout)
297 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
298
299 // Iterate through all threads until it have been determined how to stop them all at a safepoint
300 unsigned int iterations = 0;
301 int steps = 0 ;
302 while(still_running > 0) {
303 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
304 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
305 ThreadSafepointState *cur_state = cur->safepoint_state();
306 if (cur_state->is_running()) {
307 cur_state->examine_state_of_thread();
308 if (!cur_state->is_running()) {
309 still_running--;
310 // consider adjusting steps downward:
311 // steps = 0
312 // steps -= NNN
313 // steps >>= 1
314 // steps = MIN(steps, 2000-100)
315 // if (iterations != 0) steps -= NNN
316 }
317 if (TraceSafepoint && Verbose) cur_state->print();
318 }
319 }
320
321 if (iterations == 0) {
322 initial_running = still_running;
323 if (PrintSafepointStatistics) {
324 begin_statistics(nof_threads, still_running);
325 }
326 }
327
328 if (still_running > 0) {
329 // Check for if it takes to long
330 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
331 print_safepoint_timeout(_spinning_timeout);
332 }
333
334 // Spin to avoid context switching.
335 // There's a tension between allowing the mutators to run (and rendezvous)
336 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
337 // a mutator might otherwise use profitably to reach a safepoint. Excessive
338 // spinning by the VM thread on a saturated system can increase rendezvous latency.
339 // Blocking or yielding incur their own penalties in the form of context switching
340 // and the resultant loss of $ residency.
341 //
342 // Further complicating matters is that yield() does not work as naively expected
343 // on many platforms -- yield() does not guarantee that any other ready threads
344 // will run. As such we revert yield_all() after some number of iterations.
345 // Yield_all() is implemented as a short unconditional sleep on some platforms.
346 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
347 // can actually increase the time it takes the VM thread to detect that a system-wide
348 // stop-the-world safepoint has been reached. In a pathological scenario such as that
349 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
350 // In that case the mutators will be stalled waiting for the safepoint to complete and the
351 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
352 // will eventually wake up and detect that all mutators are safe, at which point
353 // we'll again make progress.
354 //
355 // Beware too that that the VMThread typically runs at elevated priority.
356 // Its default priority is higher than the default mutator priority.
357 // Obviously, this complicates spinning.
358 //
359 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
360 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
361 //
362 // See the comments in synchronizer.cpp for additional remarks on spinning.
363 //
364 // In the future we might:
365 // 1. Modify the safepoint scheme to avoid potentally unbounded spinning.
366 // This is tricky as the path used by a thread exiting the JVM (say on
367 // on JNI call-out) simply stores into its state field. The burden
368 // is placed on the VM thread, which must poll (spin).
369 // 2. Find something useful to do while spinning. If the safepoint is GC-related
370 // we might aggressively scan the stacks of threads that are already safe.
371 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
372 // If all the mutators are ONPROC there's no reason to sleep or yield.
373 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
374 // 5. Check system saturation. If the system is not fully saturated then
375 // simply spin and avoid sleep/yield.
376 // 6. As still-running mutators rendezvous they could unpark the sleeping
377 // VMthread. This works well for still-running mutators that become
378 // safe. The VMthread must still poll for mutators that call-out.
379 // 7. Drive the policy on time-since-begin instead of iterations.
380 // 8. Consider making the spin duration a function of the # of CPUs:
381 // Spin = (((ncpus-1) * M) + K) + F(still_running)
382 // Alternately, instead of counting iterations of the outer loop
383 // we could count the # of threads visited in the inner loop, above.
384 // 9. On windows consider using the return value from SwitchThreadTo()
385 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
386
387 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
388 guarantee (PageArmed == 0, "invariant") ;
389 PageArmed = 1 ;
390 os::make_polling_page_unreadable();
391 }
392
393 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
394 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
395 ++steps ;
396 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
397 SpinPause() ; // MP-Polite spin
398 } else
399 if (steps < DeferThrSuspendLoopCount) {
400 os::NakedYield() ;
401 } else {
402 os::yield_all(steps) ;
403 // Alternately, the VM thread could transiently depress its scheduling priority or
404 // transiently increase the priority of the tardy mutator(s).
405 }
406
407 iterations ++ ;
408 }
409 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
410 }
411 assert(still_running == 0, "sanity check");
412
413 if (PrintSafepointStatistics) {
414 update_statistics_on_spin_end();
415 }
416
417 if (sync_event.should_commit()) {
418 post_safepoint_synchronize_event(&sync_event, initial_running, _waiting_to_block, iterations);
419 }
420
421 // wait until all threads are stopped
422 {
423 EventSafepointWaitBlocked wait_blocked_event;
424 int initial_waiting_to_block = _waiting_to_block;
425
426 while (_waiting_to_block > 0) {
427 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
428 if (!SafepointTimeout || timeout_error_printed) {
429 Safepoint_lock->wait(true); // true, means with no safepoint checks
430 } else {
431 // Compute remaining time
432 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
433
434 // If there is no remaining time, then there is an error
435 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
436 print_safepoint_timeout(_blocking_timeout);
437 }
438 }
439 }
440 assert(_waiting_to_block == 0, "sanity check");
441
442 #ifndef PRODUCT
443 if (SafepointTimeout) {
444 jlong current_time = os::javaTimeNanos();
445 if (safepoint_limit_time < current_time) {
446 tty->print_cr("# SafepointSynchronize: Finished after "
447 INT64_FORMAT_W(6) " ms",
448 ((current_time - safepoint_limit_time) / MICROUNITS +
449 SafepointTimeoutDelay));
450 }
451 }
452 #endif
453
454 assert((_safepoint_counter & 0x1) == 0, "must be even");
455 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
456 _safepoint_counter ++;
457
458 // Record state
459 _state = _synchronized;
460
461 OrderAccess::fence();
462
463 if (wait_blocked_event.should_commit()) {
464 post_safepoint_wait_blocked_event(&wait_blocked_event, initial_waiting_to_block);
465 }
466 }
467
468 #ifdef ASSERT
469 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
470 // make sure all the threads were visited
471 assert(cur->was_visited_for_critical_count(), "missed a thread");
472 }
473 #endif // ASSERT
474
475 // Update the count of active JNI critical regions
476 GC_locker::set_jni_lock_count(_current_jni_active_count);
477
478 if (TraceSafepoint) {
479 VM_Operation *op = VMThread::vm_operation();
480 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
481 }
482
483 RuntimeService::record_safepoint_synchronized();
484 if (PrintSafepointStatistics) {
485 update_statistics_on_sync_end(os::javaTimeNanos());
486 }
487
488 // Call stuff that needs to be run when a safepoint is just about to be completed
489 {
490 EventSafepointCleanup cleanup_event;
491 do_cleanup_tasks();
492 if (cleanup_event.should_commit()) {
493 post_safepoint_cleanup_event(&cleanup_event);
494 }
495 }
496
497 if (PrintSafepointStatistics) {
498 // Record how much time spend on the above cleanup tasks
499 update_statistics_on_cleanup_end(os::javaTimeNanos());
500 }
501
502 if (begin_event.should_commit()) {
503 post_safepoint_begin_event(&begin_event, nof_threads, _current_jni_active_count);
504 }
505 }
506
507 // Wake up all threads, so they are ready to resume execution after the safepoint
508 // operation has been carried out
509 void SafepointSynchronize::end() {
510
511 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
512 assert((_safepoint_counter & 0x1) == 1, "must be odd");
513 EventSafepointEnd event;
514 _safepoint_counter ++;
515 // memory fence isn't required here since an odd _safepoint_counter
516 // value can do no harm and a fence is issued below anyway.
517
518 DEBUG_ONLY(Thread* myThread = Thread::current();)
519 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
520
521 if (PrintSafepointStatistics) {
522 end_statistics(os::javaTimeNanos());
523 }
524
525 #ifdef ASSERT
526 // A pending_exception cannot be installed during a safepoint. The threads
527 // may install an async exception after they come back from a safepoint into
528 // pending_exception after they unblock. But that should happen later.
529 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
530 assert (!(cur->has_pending_exception() &&
531 cur->safepoint_state()->is_at_poll_safepoint()),
532 "safepoint installed a pending exception");
533 }
534 #endif // ASSERT
535
536 if (PageArmed) {
537 // Make polling safepoint aware
538 os::make_polling_page_readable();
539 PageArmed = 0 ;
540 }
541
542 // Remove safepoint check from interpreter
543 Interpreter::ignore_safepoints();
544
545 {
546 MutexLocker mu(Safepoint_lock);
547
548 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
549
550 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
551 // when they get restarted.
552 _state = _not_synchronized;
553 OrderAccess::fence();
554
555 if (TraceSafepoint) {
556 tty->print_cr("Leaving safepoint region");
557 }
558
559 // Start suspended threads
560 for(JavaThread *current = Threads::first(); current; current = current->next()) {
561 // A problem occurring on Solaris is when attempting to restart threads
562 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
563 // to the next one (since it has been running the longest). We then have
564 // to wait for a cpu to become available before we can continue restarting
565 // threads.
566 // FIXME: This causes the performance of the VM to degrade when active and with
567 // large numbers of threads. Apparently this is due to the synchronous nature
568 // of suspending threads.
569 //
570 // TODO-FIXME: the comments above are vestigial and no longer apply.
571 // Furthermore, using solaris' schedctl in this particular context confers no benefit
572 if (VMThreadHintNoPreempt) {
573 os::hint_no_preempt();
574 }
575 ThreadSafepointState* cur_state = current->safepoint_state();
576 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
577 cur_state->restart();
578 assert(cur_state->is_running(), "safepoint state has not been reset");
579 }
580
581 RuntimeService::record_safepoint_end();
582
583 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
584 // blocked in signal_thread_blocked
585 Threads_lock->unlock();
586
587 }
588 #if INCLUDE_ALL_GCS
589 // If there are any concurrent GC threads resume them.
590 if (UseConcMarkSweepGC) {
591 ConcurrentMarkSweepThread::desynchronize(false);
592 } else if (UseG1GC || (UseShenandoahGC && UseStringDeduplication)) {
593 SuspendibleThreadSet::desynchronize();
594 }
595 #endif // INCLUDE_ALL_GCS
596 // record this time so VMThread can keep track how much time has elasped
597 // since last safepoint.
598 _end_of_last_safepoint = os::javaTimeMillis();
599 if (event.should_commit()) {
600 post_safepoint_end_event(&event);
601 }
602 }
603
604 bool SafepointSynchronize::is_cleanup_needed() {
605 // Need a safepoint if some inline cache buffers is non-empty
606 if (!InlineCacheBuffer::is_empty()) return true;
607 return false;
608 }
609
610
611
612 // Various cleaning tasks that should be done periodically at safepoints
613 void SafepointSynchronize::do_cleanup_tasks() {
614 {
615 const char* name = "deflating idle monitors";
616 EventSafepointCleanupTask event;
617 TraceTime t1(name, TraceSafepointCleanupTime);
618 ObjectSynchronizer::deflate_idle_monitors();
619 if (event.should_commit()) {
620 post_safepoint_cleanup_task_event(&event, name);
621 }
622 }
623
624 {
625 const char* name = "updating inline caches";
626 EventSafepointCleanupTask event;
627 TraceTime t2(name, TraceSafepointCleanupTime);
628 InlineCacheBuffer::update_inline_caches();
629 if (event.should_commit()) {
630 post_safepoint_cleanup_task_event(&event, name);
631 }
632 }
633 {
634 const char* name = "compilation policy safepoint handler";
635 EventSafepointCleanupTask event;
636 TraceTime t3(name, TraceSafepointCleanupTime);
637 CompilationPolicy::policy()->do_safepoint_work();
638 if (event.should_commit()) {
639 post_safepoint_cleanup_task_event(&event, name);
640 }
641 }
642
643 {
644 const char* name = "mark nmethods";
645 EventSafepointCleanupTask event;
646 TraceTime t4(name, TraceSafepointCleanupTime);
647 NMethodSweeper::mark_active_nmethods();
648 if (event.should_commit()) {
649 post_safepoint_cleanup_task_event(&event, name);
650 }
651 }
652
653 if (SymbolTable::needs_rehashing()) {
654 const char* name = "rehashing symbol table";
655 EventSafepointCleanupTask event;
656 TraceTime t5(name, TraceSafepointCleanupTime);
657 SymbolTable::rehash_table();
658 if (event.should_commit()) {
659 post_safepoint_cleanup_task_event(&event, name);
660 }
661 }
662
663 if (StringTable::needs_rehashing()) {
664 const char* name = "rehashing string table";
665 EventSafepointCleanupTask event;
666 TraceTime t6(name, TraceSafepointCleanupTime);
667 StringTable::rehash_table();
668 if (event.should_commit()) {
669 post_safepoint_cleanup_task_event(&event, name);
670 }
671 }
672
673 // rotate log files?
674 if (UseGCLogFileRotation) {
675 TraceTime t8("rotating gc logs", TraceSafepointCleanupTime);
676 gclog_or_tty->rotate_log(false);
677 }
678
679 {
680 // CMS delays purging the CLDG until the beginning of the next safepoint and to
681 // make sure concurrent sweep is done
682 TraceTime t7("purging class loader data graph", TraceSafepointCleanupTime);
683 ClassLoaderDataGraph::purge_if_needed();
684 }
685 }
686
687
688 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
689 switch(state) {
690 case _thread_in_native:
691 // native threads are safe if they have no java stack or have walkable stack
692 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
693
694 // blocked threads should have already have walkable stack
695 case _thread_blocked:
696 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
697 return true;
698
699 default:
700 return false;
701 }
702 }
703
704
705 // See if the thread is running inside a lazy critical native and
706 // update the thread critical count if so. Also set a suspend flag to
707 // cause the native wrapper to return into the JVM to do the unlock
708 // once the native finishes.
709 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
710 if (state == _thread_in_native &&
711 thread->has_last_Java_frame() &&
712 thread->frame_anchor()->walkable()) {
713 // This thread might be in a critical native nmethod so look at
714 // the top of the stack and increment the critical count if it
715 // is.
716 frame wrapper_frame = thread->last_frame();
717 CodeBlob* stub_cb = wrapper_frame.cb();
718 if (stub_cb != NULL &&
719 stub_cb->is_nmethod() &&
720 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
721 // A thread could potentially be in a critical native across
722 // more than one safepoint, so only update the critical state on
723 // the first one. When it returns it will perform the unlock.
724 if (!thread->do_critical_native_unlock()) {
725 #ifdef ASSERT
726 if (!thread->in_critical()) {
727 GC_locker::increment_debug_jni_lock_count();
728 }
729 #endif
730 thread->enter_critical();
731 // Make sure the native wrapper calls back on return to
732 // perform the needed critical unlock.
733 thread->set_critical_native_unlock();
734 }
735 }
736 }
737 }
738
739
740
741 // -------------------------------------------------------------------------------------------------------
742 // Implementation of Safepoint callback point
743
744 void SafepointSynchronize::block(JavaThread *thread) {
745 assert(thread != NULL, "thread must be set");
746 assert(thread->is_Java_thread(), "not a Java thread");
747
748 // Threads shouldn't block if they are in the middle of printing, but...
749 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
750
751 // Only bail from the block() call if the thread is gone from the
752 // thread list; starting to exit should still block.
753 if (thread->is_terminated()) {
754 // block current thread if we come here from native code when VM is gone
755 thread->block_if_vm_exited();
756
757 // otherwise do nothing
758 return;
759 }
760
761 JavaThreadState state = thread->thread_state();
762 thread->frame_anchor()->make_walkable(thread);
763
764 // Check that we have a valid thread_state at this point
765 switch(state) {
766 case _thread_in_vm_trans:
767 case _thread_in_Java: // From compiled code
768
769 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
770 // we pretend we are still in the VM.
771 thread->set_thread_state(_thread_in_vm);
772
773 if (is_synchronizing()) {
774 Atomic::inc (&TryingToBlock) ;
775 }
776
777 // We will always be holding the Safepoint_lock when we are examine the state
778 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
779 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
780 Safepoint_lock->lock_without_safepoint_check();
781 if (is_synchronizing()) {
782 // Decrement the number of threads to wait for and signal vm thread
783 assert(_waiting_to_block > 0, "sanity check");
784 _waiting_to_block--;
785 thread->safepoint_state()->set_has_called_back(true);
786
787 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
788 if (thread->in_critical()) {
789 // Notice that this thread is in a critical section
790 increment_jni_active_count();
791 }
792
793 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
794 if (_waiting_to_block == 0) {
795 Safepoint_lock->notify_all();
796 }
797 }
798
799 // We transition the thread to state _thread_blocked here, but
800 // we can't do our usual check for external suspension and then
801 // self-suspend after the lock_without_safepoint_check() call
802 // below because we are often called during transitions while
803 // we hold different locks. That would leave us suspended while
804 // holding a resource which results in deadlocks.
805 thread->set_thread_state(_thread_blocked);
806 Safepoint_lock->unlock();
807
808 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
809 // the entire safepoint, the threads will all line up here during the safepoint.
810 Threads_lock->lock_without_safepoint_check();
811 // restore original state. This is important if the thread comes from compiled code, so it
812 // will continue to execute with the _thread_in_Java state.
813 thread->set_thread_state(state);
814 Threads_lock->unlock();
815 break;
816
817 case _thread_in_native_trans:
818 case _thread_blocked_trans:
819 case _thread_new_trans:
820 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
821 thread->print_thread_state();
822 fatal("Deadlock in safepoint code. "
823 "Should have called back to the VM before blocking.");
824 }
825
826 // We transition the thread to state _thread_blocked here, but
827 // we can't do our usual check for external suspension and then
828 // self-suspend after the lock_without_safepoint_check() call
829 // below because we are often called during transitions while
830 // we hold different locks. That would leave us suspended while
831 // holding a resource which results in deadlocks.
832 thread->set_thread_state(_thread_blocked);
833
834 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
835 // the safepoint code might still be waiting for it to block. We need to change the state here,
836 // so it can see that it is at a safepoint.
837
838 // Block until the safepoint operation is completed.
839 Threads_lock->lock_without_safepoint_check();
840
841 // Restore state
842 thread->set_thread_state(state);
843
844 Threads_lock->unlock();
845 break;
846
847 default:
848 fatal(err_msg("Illegal threadstate encountered: %d", state));
849 }
850
851 // Check for pending. async. exceptions or suspends - except if the
852 // thread was blocked inside the VM. has_special_runtime_exit_condition()
853 // is called last since it grabs a lock and we only want to do that when
854 // we must.
855 //
856 // Note: we never deliver an async exception at a polling point as the
857 // compiler may not have an exception handler for it. The polling
858 // code will notice the async and deoptimize and the exception will
859 // be delivered. (Polling at a return point is ok though). Sure is
860 // a lot of bother for a deprecated feature...
861 //
862 // We don't deliver an async exception if the thread state is
863 // _thread_in_native_trans so JNI functions won't be called with
864 // a surprising pending exception. If the thread state is going back to java,
865 // async exception is checked in check_special_condition_for_native_trans().
866
867 if (state != _thread_blocked_trans &&
868 state != _thread_in_vm_trans &&
869 thread->has_special_runtime_exit_condition()) {
870 thread->handle_special_runtime_exit_condition(
871 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
872 }
873 }
874
875 // ------------------------------------------------------------------------------------------------------
876 // Exception handlers
877
878
879 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
880 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
881 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
882 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
883
884 if (ShowSafepointMsgs) {
885 tty->print("handle_polling_page_exception: ");
886 }
887
888 if (PrintSafepointStatistics) {
889 inc_page_trap_count();
890 }
891
892 ThreadSafepointState* state = thread->safepoint_state();
893
894 state->handle_polling_page_exception();
895 }
896
897
898 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
899 if (!timeout_error_printed) {
900 timeout_error_printed = true;
901 // Print out the thread infor which didn't reach the safepoint for debugging
902 // purposes (useful when there are lots of threads in the debugger).
903 tty->cr();
904 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
905 if (reason == _spinning_timeout) {
906 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
907 } else if (reason == _blocking_timeout) {
908 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
909 }
910
911 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
912 ThreadSafepointState *cur_state;
913 ResourceMark rm;
914 for(JavaThread *cur_thread = Threads::first(); cur_thread;
915 cur_thread = cur_thread->next()) {
916 cur_state = cur_thread->safepoint_state();
917
918 if (cur_thread->thread_state() != _thread_blocked &&
919 ((reason == _spinning_timeout && cur_state->is_running()) ||
920 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
921 tty->print("# ");
922 cur_thread->print();
923 tty->cr();
924 }
925 }
926 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
927 }
928
929 // To debug the long safepoint, specify both AbortVMOnSafepointTimeout &
930 // ShowMessageBoxOnError.
931 if (AbortVMOnSafepointTimeout) {
932 char msg[1024];
933 VM_Operation *op = VMThread::vm_operation();
934 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
935 SafepointTimeoutDelay,
936 op != NULL ? op->name() : "no vm operation");
937 fatal(msg);
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 _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 _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
1085 // Block the thread at the safepoint poll or poll return.
1086 void ThreadSafepointState::handle_polling_page_exception() {
1087
1088 // Check state. block() will set thread state to thread_in_vm which will
1089 // cause the safepoint state _type to become _call_back.
1090 assert(type() == ThreadSafepointState::_running,
1091 "polling page exception on thread not running state");
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, 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_nmethod(), "return address should be in nmethod");
1101 nmethod* nm = (nmethod*)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 HandleMark hm(thread());
1122 Handle return_value;
1123 if (return_oop) {
1124 // The oop result has been saved on the stack together with all
1125 // the other registers. In order to preserve it over GCs we need
1126 // to keep it in a handle.
1127 oop result = caller_fr.saved_oop_result(&map);
1128 assert(result == NULL || result->is_oop(), "must be oop");
1129 return_value = Handle(thread(), result);
1130 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1131 }
1132
1133 // Block the thread
1134 SafepointSynchronize::block(thread());
1135
1136 // restore oop result, if any
1137 if (return_oop) {
1138 caller_fr.set_saved_oop_result(&map, return_value());
1139 }
1140 }
1141
1142 // This is a safepoint poll. Verify the return address and block.
1143 else {
1144 set_at_poll_safepoint(true);
1145
1146 // verify the blob built the "return address" correctly
1147 assert(real_return_addr == caller_fr.pc(), "must match");
1148
1149 // Block the thread
1150 SafepointSynchronize::block(thread());
1151 set_at_poll_safepoint(false);
1152
1153 // If we have a pending async exception deoptimize the frame
1154 // as otherwise we may never deliver it.
1155 if (thread()->has_async_condition()) {
1156 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1157 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1158 }
1159
1160 // If an exception has been installed we must check for a pending deoptimization
1161 // Deoptimize frame if exception has been thrown.
1162
1163 if (thread()->has_pending_exception() ) {
1164 RegisterMap map(thread(), true);
1165 frame caller_fr = stub_fr.sender(&map);
1166 if (caller_fr.is_deoptimized_frame()) {
1167 // The exception patch will destroy registers that are still
1168 // live and will be needed during deoptimization. Defer the
1169 // Async exception should have defered the exception until the
1170 // next safepoint which will be detected when we get into
1171 // the interpreter so if we have an exception now things
1172 // are messed up.
1173
1174 fatal("Exception installed and deoptimization is pending");
1175 }
1176 }
1177 }
1178 }
1179
1180
1181 //
1182 // Statistics & Instrumentations
1183 //
1184 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1185 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1186 int SafepointSynchronize::_cur_stat_index = 0;
1187 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1188 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1189 jlong SafepointSynchronize::_max_sync_time = 0;
1190 jlong SafepointSynchronize::_max_vmop_time = 0;
1191 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1192
1193 static jlong cleanup_end_time = 0;
1194 static bool need_to_track_page_armed_status = false;
1195 static bool init_done = false;
1196
1197 // Helper method to print the header.
1198 static void print_header() {
1199 tty->print(" vmop "
1200 "[threads: total initially_running wait_to_block] ");
1201 tty->print("[time: spin block sync cleanup vmop] ");
1202
1203 // no page armed status printed out if it is always armed.
1204 if (need_to_track_page_armed_status) {
1205 tty->print("page_armed ");
1206 }
1207
1208 tty->print_cr("page_trap_count");
1209 }
1210
1211 void SafepointSynchronize::deferred_initialize_stat() {
1212 if (init_done) return;
1213
1214 if (PrintSafepointStatisticsCount <= 0) {
1215 fatal("Wrong PrintSafepointStatisticsCount");
1216 }
1217
1218 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1219 // be printed right away, in which case, _safepoint_stats will regress to
1220 // a single element array. Otherwise, it is a circular ring buffer with default
1221 // size of PrintSafepointStatisticsCount.
1222 int stats_array_size;
1223 if (PrintSafepointStatisticsTimeout > 0) {
1224 stats_array_size = 1;
1225 PrintSafepointStatistics = true;
1226 } else {
1227 stats_array_size = PrintSafepointStatisticsCount;
1228 }
1229 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1230 * sizeof(SafepointStats), mtInternal);
1231 guarantee(_safepoint_stats != NULL,
1232 "not enough memory for safepoint instrumentation data");
1233
1234 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
1235 need_to_track_page_armed_status = true;
1236 }
1237 init_done = true;
1238 }
1239
1240 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1241 assert(init_done, "safepoint statistics array hasn't been initialized");
1242 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1243
1244 spstat->_time_stamp = _ts_of_current_safepoint;
1245
1246 VM_Operation *op = VMThread::vm_operation();
1247 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1248 if (op != NULL) {
1249 _safepoint_reasons[spstat->_vmop_type]++;
1250 }
1251
1252 spstat->_nof_total_threads = nof_threads;
1253 spstat->_nof_initial_running_threads = nof_running;
1254 spstat->_nof_threads_hit_page_trap = 0;
1255
1256 // Records the start time of spinning. The real time spent on spinning
1257 // will be adjusted when spin is done. Same trick is applied for time
1258 // spent on waiting for threads to block.
1259 if (nof_running != 0) {
1260 spstat->_time_to_spin = os::javaTimeNanos();
1261 } else {
1262 spstat->_time_to_spin = 0;
1263 }
1264 }
1265
1266 void SafepointSynchronize::update_statistics_on_spin_end() {
1267 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1268
1269 jlong cur_time = os::javaTimeNanos();
1270
1271 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1272 if (spstat->_nof_initial_running_threads != 0) {
1273 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1274 }
1275
1276 if (need_to_track_page_armed_status) {
1277 spstat->_page_armed = (PageArmed == 1);
1278 }
1279
1280 // Records the start time of waiting for to block. Updated when block is done.
1281 if (_waiting_to_block != 0) {
1282 spstat->_time_to_wait_to_block = cur_time;
1283 } else {
1284 spstat->_time_to_wait_to_block = 0;
1285 }
1286 }
1287
1288 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1289 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1290
1291 if (spstat->_nof_threads_wait_to_block != 0) {
1292 spstat->_time_to_wait_to_block = end_time -
1293 spstat->_time_to_wait_to_block;
1294 }
1295
1296 // Records the end time of sync which will be used to calculate the total
1297 // vm operation time. Again, the real time spending in syncing will be deducted
1298 // from the start of the sync time later when end_statistics is called.
1299 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1300 if (spstat->_time_to_sync > _max_sync_time) {
1301 _max_sync_time = spstat->_time_to_sync;
1302 }
1303
1304 spstat->_time_to_do_cleanups = end_time;
1305 }
1306
1307 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1308 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1309
1310 // Record how long spent in cleanup tasks.
1311 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1312
1313 cleanup_end_time = end_time;
1314 }
1315
1316 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1317 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1318
1319 // Update the vm operation time.
1320 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1321 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1322 _max_vmop_time = spstat->_time_to_exec_vmop;
1323 }
1324 // Only the sync time longer than the specified
1325 // PrintSafepointStatisticsTimeout will be printed out right away.
1326 // By default, it is -1 meaning all samples will be put into the list.
1327 if ( PrintSafepointStatisticsTimeout > 0) {
1328 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1329 print_statistics();
1330 }
1331 } else {
1332 // The safepoint statistics will be printed out when the _safepoin_stats
1333 // array fills up.
1334 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1335 print_statistics();
1336 _cur_stat_index = 0;
1337 } else {
1338 _cur_stat_index++;
1339 }
1340 }
1341 }
1342
1343 void SafepointSynchronize::print_statistics() {
1344 SafepointStats* sstats = _safepoint_stats;
1345
1346 for (int index = 0; index <= _cur_stat_index; index++) {
1347 if (index % 30 == 0) {
1348 print_header();
1349 }
1350 sstats = &_safepoint_stats[index];
1351 tty->print("%.3f: ", sstats->_time_stamp);
1352 tty->print("%-26s ["
1353 INT32_FORMAT_W(8) INT32_FORMAT_W(11) INT32_FORMAT_W(15)
1354 " ] ",
1355 sstats->_vmop_type == -1 ? "no vm operation" :
1356 VM_Operation::name(sstats->_vmop_type),
1357 sstats->_nof_total_threads,
1358 sstats->_nof_initial_running_threads,
1359 sstats->_nof_threads_wait_to_block);
1360 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1361 tty->print(" ["
1362 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1363 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1364 INT64_FORMAT_W(6) " ] ",
1365 sstats->_time_to_spin / MICROUNITS,
1366 sstats->_time_to_wait_to_block / MICROUNITS,
1367 sstats->_time_to_sync / MICROUNITS,
1368 sstats->_time_to_do_cleanups / MICROUNITS,
1369 sstats->_time_to_exec_vmop / MICROUNITS);
1370
1371 if (need_to_track_page_armed_status) {
1372 tty->print(INT32_FORMAT " ", sstats->_page_armed);
1373 }
1374 tty->print_cr(INT32_FORMAT " ", sstats->_nof_threads_hit_page_trap);
1375 }
1376 }
1377
1378 // This method will be called when VM exits. It will first call
1379 // print_statistics to print out the rest of the sampling. Then
1380 // it tries to summarize the sampling.
1381 void SafepointSynchronize::print_stat_on_exit() {
1382 if (_safepoint_stats == NULL) return;
1383
1384 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1385
1386 // During VM exit, end_statistics may not get called and in that
1387 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1388 // don't print it out.
1389 // Approximate the vm op time.
1390 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1391 os::javaTimeNanos() - cleanup_end_time;
1392
1393 if ( PrintSafepointStatisticsTimeout < 0 ||
1394 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1395 print_statistics();
1396 }
1397 tty->cr();
1398
1399 // Print out polling page sampling status.
1400 if (!need_to_track_page_armed_status) {
1401 if (UseCompilerSafepoints) {
1402 tty->print_cr("Polling page always armed");
1403 }
1404 } else {
1405 tty->print_cr("Defer polling page loop count = %d\n",
1406 DeferPollingPageLoopCount);
1407 }
1408
1409 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1410 if (_safepoint_reasons[index] != 0) {
1411 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1412 _safepoint_reasons[index]);
1413 }
1414 }
1415
1416 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1417 _coalesced_vmop_count);
1418 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1419 _max_sync_time / MICROUNITS);
1420 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1421 INT64_FORMAT_W(5) " ms",
1422 _max_vmop_time / MICROUNITS);
1423 }
1424
1425 // ------------------------------------------------------------------------------------------------
1426 // Non-product code
1427
1428 #ifndef PRODUCT
1429
1430 void SafepointSynchronize::print_state() {
1431 if (_state == _not_synchronized) {
1432 tty->print_cr("not synchronized");
1433 } else if (_state == _synchronizing || _state == _synchronized) {
1434 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1435 "synchronized");
1436
1437 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1438 cur->safepoint_state()->print();
1439 }
1440 }
1441 }
1442
1443 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1444 if (ShowSafepointMsgs) {
1445 va_list ap;
1446 va_start(ap, format);
1447 tty->vprint_cr(format, ap);
1448 va_end(ap);
1449 }
1450 }
1451
1452 #endif // !PRODUCT