1 /*
2 * Copyright (c) 1997, 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/stringTable.hpp"
27 #include "classfile/symbolTable.hpp"
28 #include "classfile/systemDictionary.hpp"
29 #include "code/codeCache.hpp"
30 #include "code/icBuffer.hpp"
31 #include "code/nmethod.hpp"
32 #include "code/pcDesc.hpp"
33 #include "code/scopeDesc.hpp"
34 #include "gc/shared/collectedHeap.hpp"
35 #include "gc/shared/gcLocker.inline.hpp"
36 #include "interpreter/interpreter.hpp"
37 #include "logging/log.hpp"
38 #include "memory/resourceArea.hpp"
39 #include "memory/universe.inline.hpp"
40 #include "oops/oop.inline.hpp"
41 #include "oops/symbol.hpp"
42 #include "runtime/atomic.hpp"
43 #include "runtime/compilationPolicy.hpp"
44 #include "runtime/deoptimization.hpp"
45 #include "runtime/frame.inline.hpp"
46 #include "runtime/interfaceSupport.hpp"
47 #include "runtime/mutexLocker.hpp"
48 #include "runtime/orderAccess.inline.hpp"
49 #include "runtime/osThread.hpp"
50 #include "runtime/safepoint.hpp"
51 #include "runtime/signature.hpp"
52 #include "runtime/stubCodeGenerator.hpp"
53 #include "runtime/stubRoutines.hpp"
54 #include "runtime/sweeper.hpp"
55 #include "runtime/synchronizer.hpp"
56 #include "runtime/thread.inline.hpp"
57 #include "runtime/timerTrace.hpp"
58 #include "services/runtimeService.hpp"
59 #include "trace/tracing.hpp"
60 #include "trace/traceMacros.hpp"
61 #include "utilities/events.hpp"
62 #include "utilities/macros.hpp"
63 #ifdef COMPILER1
64 #include "c1/c1_globals.hpp"
65 #endif
66
67 // --------------------------------------------------------------------------------------------------
68 // Implementation of Safepoint begin/end
69
70 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
71 volatile int SafepointSynchronize::_waiting_to_block = 0;
72 volatile int SafepointSynchronize::_safepoint_counter = 0;
73 int SafepointSynchronize::_current_jni_active_count = 0;
74 long SafepointSynchronize::_end_of_last_safepoint = 0;
75 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
76 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
77 static bool timeout_error_printed = false;
78
79 // Roll all threads forward to a safepoint and suspend them all
80 void SafepointSynchronize::begin() {
81 EventSafepointBegin begin_event;
82 Thread* myThread = Thread::current();
83 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
84
85 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
86 _safepoint_begin_time = os::javaTimeNanos();
87 _ts_of_current_safepoint = tty->time_stamp().seconds();
88 }
89
90 GC::gc()->synchronize_safepoint();
91
92 // By getting the Threads_lock, we assure that no threads are about to start or
93 // exit. It is released again in SafepointSynchronize::end().
94 Threads_lock->lock();
95
96 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
97
98 int nof_threads = Threads::number_of_threads();
99
100 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads);
101
102 RuntimeService::record_safepoint_begin();
103
104 MutexLocker mu(Safepoint_lock);
105
106 // Reset the count of active JNI critical threads
107 _current_jni_active_count = 0;
108
109 // Set number of threads to wait for, before we initiate the callbacks
110 _waiting_to_block = nof_threads;
111 TryingToBlock = 0 ;
112 int still_running = nof_threads;
113
114 // Save the starting time, so that it can be compared to see if this has taken
115 // too long to complete.
116 jlong safepoint_limit_time = 0;
117 timeout_error_printed = false;
118
119 // PrintSafepointStatisticsTimeout can be specified separately. When
120 // specified, PrintSafepointStatistics will be set to true in
121 // deferred_initialize_stat method. The initialization has to be done
122 // early enough to avoid any races. See bug 6880029 for details.
123 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
124 deferred_initialize_stat();
125 }
126
127 // Begin the process of bringing the system to a safepoint.
128 // Java threads can be in several different states and are
129 // stopped by different mechanisms:
130 //
131 // 1. Running interpreted
132 // The interpreter dispatch table is changed to force it to
133 // check for a safepoint condition between bytecodes.
134 // 2. Running in native code
135 // When returning from the native code, a Java thread must check
136 // the safepoint _state to see if we must block. If the
137 // VM thread sees a Java thread in native, it does
138 // not wait for this thread to block. The order of the memory
139 // writes and reads of both the safepoint state and the Java
140 // threads state is critical. In order to guarantee that the
141 // memory writes are serialized with respect to each other,
142 // the VM thread issues a memory barrier instruction
143 // (on MP systems). In order to avoid the overhead of issuing
144 // a memory barrier for each Java thread making native calls, each Java
145 // thread performs a write to a single memory page after changing
146 // the thread state. The VM thread performs a sequence of
147 // mprotect OS calls which forces all previous writes from all
148 // Java threads to be serialized. This is done in the
149 // os::serialize_thread_states() call. This has proven to be
150 // much more efficient than executing a membar instruction
151 // on every call to native code.
152 // 3. Running compiled Code
153 // Compiled code reads a global (Safepoint Polling) page that
154 // is set to fault if we are trying to get to a safepoint.
155 // 4. Blocked
156 // A thread which is blocked will not be allowed to return from the
157 // block condition until the safepoint operation is complete.
158 // 5. In VM or Transitioning between states
159 // If a Java thread is currently running in the VM or transitioning
160 // between states, the safepointing code will wait for the thread to
161 // block itself when it attempts transitions to a new state.
162 //
163 {
164 EventSafepointStateSynchronization sync_event;
165 int initial_running = 0;
166
167 _state = _synchronizing;
168 OrderAccess::fence();
169
170 // Flush all thread states to memory
171 if (!UseMembar) {
172 os::serialize_thread_states();
173 }
174
175 // Make interpreter safepoint aware
176 Interpreter::notice_safepoints();
177
178 if (DeferPollingPageLoopCount < 0) {
179 // Make polling safepoint aware
180 guarantee (PageArmed == 0, "invariant") ;
181 PageArmed = 1 ;
182 os::make_polling_page_unreadable();
183 }
184
185 // Consider using active_processor_count() ... but that call is expensive.
186 int ncpus = os::processor_count() ;
187
188 #ifdef ASSERT
189 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
190 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
191 // Clear the visited flag to ensure that the critical counts are collected properly.
192 cur->set_visited_for_critical_count(false);
193 }
194 #endif // ASSERT
195
196 if (SafepointTimeout)
197 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
198
199 // Iterate through all threads until it have been determined how to stop them all at a safepoint
200 unsigned int iterations = 0;
201 int steps = 0 ;
202 while(still_running > 0) {
203 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
204 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
205 ThreadSafepointState *cur_state = cur->safepoint_state();
206 if (cur_state->is_running()) {
207 cur_state->examine_state_of_thread();
208 if (!cur_state->is_running()) {
209 still_running--;
210 // consider adjusting steps downward:
211 // steps = 0
212 // steps -= NNN
213 // steps >>= 1
214 // steps = MIN(steps, 2000-100)
215 // if (iterations != 0) steps -= NNN
216 }
217 if (log_is_enabled(Trace, safepoint)) {
218 ResourceMark rm;
219 cur_state->print_on(Log(safepoint)::trace_stream());
220 }
221 }
222 }
223
224 if (iterations == 0) {
225 initial_running = still_running;
226 if (PrintSafepointStatistics) {
227 begin_statistics(nof_threads, still_running);
228 }
229 }
230
231 if (still_running > 0) {
232 // Check for if it takes to long
233 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
234 print_safepoint_timeout(_spinning_timeout);
235 }
236
237 // Spin to avoid context switching.
238 // There's a tension between allowing the mutators to run (and rendezvous)
239 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
240 // a mutator might otherwise use profitably to reach a safepoint. Excessive
241 // spinning by the VM thread on a saturated system can increase rendezvous latency.
242 // Blocking or yielding incur their own penalties in the form of context switching
243 // and the resultant loss of $ residency.
244 //
245 // Further complicating matters is that yield() does not work as naively expected
246 // on many platforms -- yield() does not guarantee that any other ready threads
247 // will run. As such we revert to naked_short_sleep() after some number of iterations.
248 // nakes_short_sleep() is implemented as a short unconditional sleep.
249 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
250 // can actually increase the time it takes the VM thread to detect that a system-wide
251 // stop-the-world safepoint has been reached. In a pathological scenario such as that
252 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
253 // In that case the mutators will be stalled waiting for the safepoint to complete and the
254 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
255 // will eventually wake up and detect that all mutators are safe, at which point
256 // we'll again make progress.
257 //
258 // Beware too that that the VMThread typically runs at elevated priority.
259 // Its default priority is higher than the default mutator priority.
260 // Obviously, this complicates spinning.
261 //
262 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
263 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
264 //
265 // See the comments in synchronizer.cpp for additional remarks on spinning.
266 //
267 // In the future we might:
268 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
269 // This is tricky as the path used by a thread exiting the JVM (say on
270 // on JNI call-out) simply stores into its state field. The burden
271 // is placed on the VM thread, which must poll (spin).
272 // 2. Find something useful to do while spinning. If the safepoint is GC-related
273 // we might aggressively scan the stacks of threads that are already safe.
274 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
275 // If all the mutators are ONPROC there's no reason to sleep or yield.
276 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
277 // 5. Check system saturation. If the system is not fully saturated then
278 // simply spin and avoid sleep/yield.
279 // 6. As still-running mutators rendezvous they could unpark the sleeping
280 // VMthread. This works well for still-running mutators that become
281 // safe. The VMthread must still poll for mutators that call-out.
282 // 7. Drive the policy on time-since-begin instead of iterations.
283 // 8. Consider making the spin duration a function of the # of CPUs:
284 // Spin = (((ncpus-1) * M) + K) + F(still_running)
285 // Alternately, instead of counting iterations of the outer loop
286 // we could count the # of threads visited in the inner loop, above.
287 // 9. On windows consider using the return value from SwitchThreadTo()
288 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
289
290 if (int(iterations) == DeferPollingPageLoopCount) {
291 guarantee (PageArmed == 0, "invariant") ;
292 PageArmed = 1 ;
293 os::make_polling_page_unreadable();
294 }
295
296 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
297 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
298 ++steps ;
299 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
300 SpinPause() ; // MP-Polite spin
301 } else
302 if (steps < DeferThrSuspendLoopCount) {
303 os::naked_yield() ;
304 } else {
305 os::naked_short_sleep(1);
306 }
307
308 iterations ++ ;
309 }
310 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
311 }
312 assert(still_running == 0, "sanity check");
313
314 if (PrintSafepointStatistics) {
315 update_statistics_on_spin_end();
316 }
317
318 if (sync_event.should_commit()) {
319 sync_event.set_safepointId(safepoint_counter());
320 sync_event.set_initialThreadCount(initial_running);
321 sync_event.set_runningThreadCount(_waiting_to_block);
322 sync_event.set_iterations(iterations);
323 sync_event.commit();
324 }
325 } //EventSafepointStateSync
326
327 // wait until all threads are stopped
328 {
329 EventSafepointWaitBlocked wait_blocked_event;
330 int initial_waiting_to_block = _waiting_to_block;
331
332 while (_waiting_to_block > 0) {
333 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
334 if (!SafepointTimeout || timeout_error_printed) {
335 Safepoint_lock->wait(true); // true, means with no safepoint checks
336 } else {
337 // Compute remaining time
338 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
339
340 // If there is no remaining time, then there is an error
341 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
342 print_safepoint_timeout(_blocking_timeout);
343 }
344 }
345 }
346 assert(_waiting_to_block == 0, "sanity check");
347
348 #ifndef PRODUCT
349 if (SafepointTimeout) {
350 jlong current_time = os::javaTimeNanos();
351 if (safepoint_limit_time < current_time) {
352 tty->print_cr("# SafepointSynchronize: Finished after "
353 INT64_FORMAT_W(6) " ms",
354 ((current_time - safepoint_limit_time) / MICROUNITS +
355 (jlong)SafepointTimeoutDelay));
356 }
357 }
358 #endif
359
360 assert((_safepoint_counter & 0x1) == 0, "must be even");
361 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
362 _safepoint_counter ++;
363
364 // Record state
365 _state = _synchronized;
366
367 OrderAccess::fence();
368
369 if (wait_blocked_event.should_commit()) {
370 wait_blocked_event.set_safepointId(safepoint_counter());
371 wait_blocked_event.set_runningThreadCount(initial_waiting_to_block);
372 wait_blocked_event.commit();
373 }
374 } // EventSafepointWaitBlocked
375
376 #ifdef ASSERT
377 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
378 // make sure all the threads were visited
379 assert(cur->was_visited_for_critical_count(), "missed a thread");
380 }
381 #endif // ASSERT
382
383 // Update the count of active JNI critical regions
384 GCLocker::set_jni_lock_count(_current_jni_active_count);
385
386 if (log_is_enabled(Debug, safepoint)) {
387 VM_Operation *op = VMThread::vm_operation();
388 log_debug(safepoint)("Entering safepoint region: %s",
389 (op != NULL) ? op->name() : "no vm operation");
390 }
391
392 RuntimeService::record_safepoint_synchronized();
393 if (PrintSafepointStatistics) {
394 update_statistics_on_sync_end(os::javaTimeNanos());
395 }
396
397 // Call stuff that needs to be run when a safepoint is just about to be completed
398 {
399 EventSafepointCleanup cleanup_event;
400 do_cleanup_tasks();
401 if (cleanup_event.should_commit()) {
402 cleanup_event.set_safepointId(safepoint_counter());
403 cleanup_event.commit();
404 }
405 }
406
407 if (PrintSafepointStatistics) {
408 // Record how much time spend on the above cleanup tasks
409 update_statistics_on_cleanup_end(os::javaTimeNanos());
410 }
411 if (begin_event.should_commit()) {
412 begin_event.set_safepointId(safepoint_counter());
413 begin_event.set_totalThreadCount(nof_threads);
414 begin_event.set_jniCriticalThreadCount(_current_jni_active_count);
415 begin_event.commit();
416 }
417 }
418
419 // Wake up all threads, so they are ready to resume execution after the safepoint
420 // operation has been carried out
421 void SafepointSynchronize::end() {
422 EventSafepointEnd event;
423 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id"
424
425 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
426 assert((_safepoint_counter & 0x1) == 1, "must be odd");
427 _safepoint_counter ++;
428 // memory fence isn't required here since an odd _safepoint_counter
429 // value can do no harm and a fence is issued below anyway.
430
431 DEBUG_ONLY(Thread* myThread = Thread::current();)
432 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
433
434 if (PrintSafepointStatistics) {
435 end_statistics(os::javaTimeNanos());
436 }
437
438 #ifdef ASSERT
439 // A pending_exception cannot be installed during a safepoint. The threads
440 // may install an async exception after they come back from a safepoint into
441 // pending_exception after they unblock. But that should happen later.
442 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
443 assert (!(cur->has_pending_exception() &&
444 cur->safepoint_state()->is_at_poll_safepoint()),
445 "safepoint installed a pending exception");
446 }
447 #endif // ASSERT
448
449 if (PageArmed) {
450 // Make polling safepoint aware
451 os::make_polling_page_readable();
452 PageArmed = 0 ;
453 }
454
455 // Remove safepoint check from interpreter
456 Interpreter::ignore_safepoints();
457
458 {
459 MutexLocker mu(Safepoint_lock);
460
461 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
462
463 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
464 // when they get restarted.
465 _state = _not_synchronized;
466 OrderAccess::fence();
467
468 log_debug(safepoint)("Leaving safepoint region");
469
470 // Start suspended threads
471 for(JavaThread *current = Threads::first(); current; current = current->next()) {
472 // A problem occurring on Solaris is when attempting to restart threads
473 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
474 // to the next one (since it has been running the longest). We then have
475 // to wait for a cpu to become available before we can continue restarting
476 // threads.
477 // FIXME: This causes the performance of the VM to degrade when active and with
478 // large numbers of threads. Apparently this is due to the synchronous nature
479 // of suspending threads.
480 //
481 // TODO-FIXME: the comments above are vestigial and no longer apply.
482 // Furthermore, using solaris' schedctl in this particular context confers no benefit
483 if (VMThreadHintNoPreempt) {
484 os::hint_no_preempt();
485 }
486 ThreadSafepointState* cur_state = current->safepoint_state();
487 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
488 cur_state->restart();
489 assert(cur_state->is_running(), "safepoint state has not been reset");
490 }
491
492 RuntimeService::record_safepoint_end();
493
494 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
495 // blocked in signal_thread_blocked
496 Threads_lock->unlock();
497
498 }
499
500 GC::gc()->desynchronize_safepoint();
501
502 // record this time so VMThread can keep track how much time has elapsed
503 // since last safepoint.
504 _end_of_last_safepoint = os::javaTimeMillis();
505
506 if (event.should_commit()) {
507 event.set_safepointId(safepoint_id);
508 event.commit();
509 }
510 }
511
512 bool SafepointSynchronize::is_cleanup_needed() {
513 // Need a safepoint if some inline cache buffers is non-empty
514 if (!InlineCacheBuffer::is_empty()) return true;
515 return false;
516 }
517
518 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) {
519 if (event.should_commit()) {
520 event.set_safepointId(SafepointSynchronize::safepoint_counter());
521 event.set_name(name);
522 event.commit();
523 }
524 }
525
526 // Various cleaning tasks that should be done periodically at safepoints
527 void SafepointSynchronize::do_cleanup_tasks() {
528 {
529 const char* name = "deflating idle monitors";
530 EventSafepointCleanupTask event;
531 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
532 ObjectSynchronizer::deflate_idle_monitors();
533 event_safepoint_cleanup_task_commit(event, name);
534 }
535
536 {
537 const char* name = "updating inline caches";
538 EventSafepointCleanupTask event;
539 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
540 InlineCacheBuffer::update_inline_caches();
541 event_safepoint_cleanup_task_commit(event, name);
542 }
543 {
544 const char* name = "compilation policy safepoint handler";
545 EventSafepointCleanupTask event;
546 TraceTime timer("compilation policy safepoint handler", TRACETIME_LOG(Info, safepoint, cleanup));
547 CompilationPolicy::policy()->do_safepoint_work();
548 event_safepoint_cleanup_task_commit(event, name);
549 }
550
551 {
552 const char* name = "mark nmethods";
553 EventSafepointCleanupTask event;
554 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
555 NMethodSweeper::mark_active_nmethods();
556 event_safepoint_cleanup_task_commit(event, name);
557 }
558
559 if (SymbolTable::needs_rehashing()) {
560 const char* name = "rehashing symbol table";
561 EventSafepointCleanupTask event;
562 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
563 SymbolTable::rehash_table();
564 event_safepoint_cleanup_task_commit(event, name);
565 }
566
567 if (StringTable::needs_rehashing()) {
568 const char* name = "rehashing string table";
569 EventSafepointCleanupTask event;
570 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
571 StringTable::rehash_table();
572 event_safepoint_cleanup_task_commit(event, name);
573 }
574
575 {
576 // CMS delays purging the CLDG until the beginning of the next safepoint and to
577 // make sure concurrent sweep is done
578 const char* name = "purging class loader data graph";
579 EventSafepointCleanupTask event;
580 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
581 ClassLoaderDataGraph::purge_if_needed();
582 event_safepoint_cleanup_task_commit(event, name);
583 }
584 }
585
586
587 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
588 switch(state) {
589 case _thread_in_native:
590 // native threads are safe if they have no java stack or have walkable stack
591 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
592
593 // blocked threads should have already have walkable stack
594 case _thread_blocked:
595 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
596 return true;
597
598 default:
599 return false;
600 }
601 }
602
603
604 // See if the thread is running inside a lazy critical native and
605 // update the thread critical count if so. Also set a suspend flag to
606 // cause the native wrapper to return into the JVM to do the unlock
607 // once the native finishes.
608 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
609 if (state == _thread_in_native &&
610 thread->has_last_Java_frame() &&
611 thread->frame_anchor()->walkable()) {
612 // This thread might be in a critical native nmethod so look at
613 // the top of the stack and increment the critical count if it
614 // is.
615 frame wrapper_frame = thread->last_frame();
616 CodeBlob* stub_cb = wrapper_frame.cb();
617 if (stub_cb != NULL &&
618 stub_cb->is_nmethod() &&
619 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
620 // A thread could potentially be in a critical native across
621 // more than one safepoint, so only update the critical state on
622 // the first one. When it returns it will perform the unlock.
623 if (!thread->do_critical_native_unlock()) {
624 #ifdef ASSERT
625 if (!thread->in_critical()) {
626 GCLocker::increment_debug_jni_lock_count();
627 }
628 #endif
629 thread->enter_critical();
630 // Make sure the native wrapper calls back on return to
631 // perform the needed critical unlock.
632 thread->set_critical_native_unlock();
633 }
634 }
635 }
636 }
637
638
639
640 // -------------------------------------------------------------------------------------------------------
641 // Implementation of Safepoint callback point
642
643 void SafepointSynchronize::block(JavaThread *thread) {
644 assert(thread != NULL, "thread must be set");
645 assert(thread->is_Java_thread(), "not a Java thread");
646
647 // Threads shouldn't block if they are in the middle of printing, but...
648 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
649
650 // Only bail from the block() call if the thread is gone from the
651 // thread list; starting to exit should still block.
652 if (thread->is_terminated()) {
653 // block current thread if we come here from native code when VM is gone
654 thread->block_if_vm_exited();
655
656 // otherwise do nothing
657 return;
658 }
659
660 JavaThreadState state = thread->thread_state();
661 thread->frame_anchor()->make_walkable(thread);
662
663 // Check that we have a valid thread_state at this point
664 switch(state) {
665 case _thread_in_vm_trans:
666 case _thread_in_Java: // From compiled code
667
668 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
669 // we pretend we are still in the VM.
670 thread->set_thread_state(_thread_in_vm);
671
672 if (is_synchronizing()) {
673 Atomic::inc (&TryingToBlock) ;
674 }
675
676 // We will always be holding the Safepoint_lock when we are examine the state
677 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
678 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
679 Safepoint_lock->lock_without_safepoint_check();
680 if (is_synchronizing()) {
681 // Decrement the number of threads to wait for and signal vm thread
682 assert(_waiting_to_block > 0, "sanity check");
683 _waiting_to_block--;
684 thread->safepoint_state()->set_has_called_back(true);
685
686 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
687 if (thread->in_critical()) {
688 // Notice that this thread is in a critical section
689 increment_jni_active_count();
690 }
691
692 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
693 if (_waiting_to_block == 0) {
694 Safepoint_lock->notify_all();
695 }
696 }
697
698 // We transition the thread to state _thread_blocked here, but
699 // we can't do our usual check for external suspension and then
700 // self-suspend after the lock_without_safepoint_check() call
701 // below because we are often called during transitions while
702 // we hold different locks. That would leave us suspended while
703 // holding a resource which results in deadlocks.
704 thread->set_thread_state(_thread_blocked);
705 Safepoint_lock->unlock();
706
707 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
708 // the entire safepoint, the threads will all line up here during the safepoint.
709 Threads_lock->lock_without_safepoint_check();
710 // restore original state. This is important if the thread comes from compiled code, so it
711 // will continue to execute with the _thread_in_Java state.
712 thread->set_thread_state(state);
713 Threads_lock->unlock();
714 break;
715
716 case _thread_in_native_trans:
717 case _thread_blocked_trans:
718 case _thread_new_trans:
719 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
720 thread->print_thread_state();
721 fatal("Deadlock in safepoint code. "
722 "Should have called back to the VM before blocking.");
723 }
724
725 // We transition the thread to state _thread_blocked here, but
726 // we can't do our usual check for external suspension and then
727 // self-suspend after the lock_without_safepoint_check() call
728 // below because we are often called during transitions while
729 // we hold different locks. That would leave us suspended while
730 // holding a resource which results in deadlocks.
731 thread->set_thread_state(_thread_blocked);
732
733 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
734 // the safepoint code might still be waiting for it to block. We need to change the state here,
735 // so it can see that it is at a safepoint.
736
737 // Block until the safepoint operation is completed.
738 Threads_lock->lock_without_safepoint_check();
739
740 // Restore state
741 thread->set_thread_state(state);
742
743 Threads_lock->unlock();
744 break;
745
746 default:
747 fatal("Illegal threadstate encountered: %d", state);
748 }
749
750 // Check for pending. async. exceptions or suspends - except if the
751 // thread was blocked inside the VM. has_special_runtime_exit_condition()
752 // is called last since it grabs a lock and we only want to do that when
753 // we must.
754 //
755 // Note: we never deliver an async exception at a polling point as the
756 // compiler may not have an exception handler for it. The polling
757 // code will notice the async and deoptimize and the exception will
758 // be delivered. (Polling at a return point is ok though). Sure is
759 // a lot of bother for a deprecated feature...
760 //
761 // We don't deliver an async exception if the thread state is
762 // _thread_in_native_trans so JNI functions won't be called with
763 // a surprising pending exception. If the thread state is going back to java,
764 // async exception is checked in check_special_condition_for_native_trans().
765
766 if (state != _thread_blocked_trans &&
767 state != _thread_in_vm_trans &&
768 thread->has_special_runtime_exit_condition()) {
769 thread->handle_special_runtime_exit_condition(
770 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
771 }
772 }
773
774 // ------------------------------------------------------------------------------------------------------
775 // Exception handlers
776
777
778 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
779 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
780 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
781 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
782
783 if (ShowSafepointMsgs) {
784 tty->print("handle_polling_page_exception: ");
785 }
786
787 if (PrintSafepointStatistics) {
788 inc_page_trap_count();
789 }
790
791 ThreadSafepointState* state = thread->safepoint_state();
792
793 state->handle_polling_page_exception();
794 }
795
796
797 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
798 if (!timeout_error_printed) {
799 timeout_error_printed = true;
800 // Print out the thread info which didn't reach the safepoint for debugging
801 // purposes (useful when there are lots of threads in the debugger).
802 tty->cr();
803 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
804 if (reason == _spinning_timeout) {
805 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
806 } else if (reason == _blocking_timeout) {
807 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
808 }
809
810 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
811 ThreadSafepointState *cur_state;
812 ResourceMark rm;
813 for(JavaThread *cur_thread = Threads::first(); cur_thread;
814 cur_thread = cur_thread->next()) {
815 cur_state = cur_thread->safepoint_state();
816
817 if (cur_thread->thread_state() != _thread_blocked &&
818 ((reason == _spinning_timeout && cur_state->is_running()) ||
819 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
820 tty->print("# ");
821 cur_thread->print();
822 tty->cr();
823 }
824 }
825 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
826 }
827
828 // To debug the long safepoint, specify both DieOnSafepointTimeout &
829 // ShowMessageBoxOnError.
830 if (DieOnSafepointTimeout) {
831 VM_Operation *op = VMThread::vm_operation();
832 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
833 SafepointTimeoutDelay,
834 op != NULL ? op->name() : "no vm operation");
835 }
836 }
837
838
839 // -------------------------------------------------------------------------------------------------------
840 // Implementation of ThreadSafepointState
841
842 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
843 _thread = thread;
844 _type = _running;
845 _has_called_back = false;
846 _at_poll_safepoint = false;
847 }
848
849 void ThreadSafepointState::create(JavaThread *thread) {
850 ThreadSafepointState *state = new ThreadSafepointState(thread);
851 thread->set_safepoint_state(state);
852 }
853
854 void ThreadSafepointState::destroy(JavaThread *thread) {
855 if (thread->safepoint_state()) {
856 delete(thread->safepoint_state());
857 thread->set_safepoint_state(NULL);
858 }
859 }
860
861 void ThreadSafepointState::examine_state_of_thread() {
862 assert(is_running(), "better be running or just have hit safepoint poll");
863
864 JavaThreadState state = _thread->thread_state();
865
866 // Save the state at the start of safepoint processing.
867 _orig_thread_state = state;
868
869 // Check for a thread that is suspended. Note that thread resume tries
870 // to grab the Threads_lock which we own here, so a thread cannot be
871 // resumed during safepoint synchronization.
872
873 // We check to see if this thread is suspended without locking to
874 // avoid deadlocking with a third thread that is waiting for this
875 // thread to be suspended. The third thread can notice the safepoint
876 // that we're trying to start at the beginning of its SR_lock->wait()
877 // call. If that happens, then the third thread will block on the
878 // safepoint while still holding the underlying SR_lock. We won't be
879 // able to get the SR_lock and we'll deadlock.
880 //
881 // We don't need to grab the SR_lock here for two reasons:
882 // 1) The suspend flags are both volatile and are set with an
883 // Atomic::cmpxchg() call so we should see the suspended
884 // state right away.
885 // 2) We're being called from the safepoint polling loop; if
886 // we don't see the suspended state on this iteration, then
887 // we'll come around again.
888 //
889 bool is_suspended = _thread->is_ext_suspended();
890 if (is_suspended) {
891 roll_forward(_at_safepoint);
892 return;
893 }
894
895 // Some JavaThread states have an initial safepoint state of
896 // running, but are actually at a safepoint. We will happily
897 // agree and update the safepoint state here.
898 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
899 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
900 roll_forward(_at_safepoint);
901 return;
902 }
903
904 if (state == _thread_in_vm) {
905 roll_forward(_call_back);
906 return;
907 }
908
909 // All other thread states will continue to run until they
910 // transition and self-block in state _blocked
911 // Safepoint polling in compiled code causes the Java threads to do the same.
912 // Note: new threads may require a malloc so they must be allowed to finish
913
914 assert(is_running(), "examine_state_of_thread on non-running thread");
915 return;
916 }
917
918 // Returns true is thread could not be rolled forward at present position.
919 void ThreadSafepointState::roll_forward(suspend_type type) {
920 _type = type;
921
922 switch(_type) {
923 case _at_safepoint:
924 SafepointSynchronize::signal_thread_at_safepoint();
925 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
926 if (_thread->in_critical()) {
927 // Notice that this thread is in a critical section
928 SafepointSynchronize::increment_jni_active_count();
929 }
930 break;
931
932 case _call_back:
933 set_has_called_back(false);
934 break;
935
936 case _running:
937 default:
938 ShouldNotReachHere();
939 }
940 }
941
942 void ThreadSafepointState::restart() {
943 switch(type()) {
944 case _at_safepoint:
945 case _call_back:
946 break;
947
948 case _running:
949 default:
950 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
951 p2i(_thread), _type);
952 _thread->print();
953 ShouldNotReachHere();
954 }
955 _type = _running;
956 set_has_called_back(false);
957 }
958
959
960 void ThreadSafepointState::print_on(outputStream *st) const {
961 const char *s = NULL;
962
963 switch(_type) {
964 case _running : s = "_running"; break;
965 case _at_safepoint : s = "_at_safepoint"; break;
966 case _call_back : s = "_call_back"; break;
967 default:
968 ShouldNotReachHere();
969 }
970
971 st->print_cr("Thread: " INTPTR_FORMAT
972 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
973 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
974 _at_poll_safepoint);
975
976 _thread->print_thread_state_on(st);
977 }
978
979 // ---------------------------------------------------------------------------------------------------------------------
980
981 // Block the thread at the safepoint poll or poll return.
982 void ThreadSafepointState::handle_polling_page_exception() {
983
984 // Check state. block() will set thread state to thread_in_vm which will
985 // cause the safepoint state _type to become _call_back.
986 assert(type() == ThreadSafepointState::_running,
987 "polling page exception on thread not running state");
988
989 // Step 1: Find the nmethod from the return address
990 if (ShowSafepointMsgs && Verbose) {
991 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
992 }
993 address real_return_addr = thread()->saved_exception_pc();
994
995 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
996 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
997 CompiledMethod* nm = (CompiledMethod*)cb;
998
999 // Find frame of caller
1000 frame stub_fr = thread()->last_frame();
1001 CodeBlob* stub_cb = stub_fr.cb();
1002 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1003 RegisterMap map(thread(), true);
1004 frame caller_fr = stub_fr.sender(&map);
1005
1006 // Should only be poll_return or poll
1007 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1008
1009 // This is a poll immediately before a return. The exception handling code
1010 // has already had the effect of causing the return to occur, so the execution
1011 // will continue immediately after the call. In addition, the oopmap at the
1012 // return point does not mark the return value as an oop (if it is), so
1013 // it needs a handle here to be updated.
1014 if( nm->is_at_poll_return(real_return_addr) ) {
1015 // See if return type is an oop.
1016 bool return_oop = nm->method()->is_returning_oop();
1017 Handle return_value;
1018 if (return_oop) {
1019 // The oop result has been saved on the stack together with all
1020 // the other registers. In order to preserve it over GCs we need
1021 // to keep it in a handle.
1022 oop result = caller_fr.saved_oop_result(&map);
1023 assert(result == NULL || result->is_oop(), "must be oop");
1024 return_value = Handle(thread(), result);
1025 assert(GC::gc()->heap()->is_in_or_null(result), "must be heap pointer");
1026 }
1027
1028 // Block the thread
1029 SafepointSynchronize::block(thread());
1030
1031 // restore oop result, if any
1032 if (return_oop) {
1033 caller_fr.set_saved_oop_result(&map, return_value());
1034 }
1035 }
1036
1037 // This is a safepoint poll. Verify the return address and block.
1038 else {
1039 set_at_poll_safepoint(true);
1040
1041 // verify the blob built the "return address" correctly
1042 assert(real_return_addr == caller_fr.pc(), "must match");
1043
1044 // Block the thread
1045 SafepointSynchronize::block(thread());
1046 set_at_poll_safepoint(false);
1047
1048 // If we have a pending async exception deoptimize the frame
1049 // as otherwise we may never deliver it.
1050 if (thread()->has_async_condition()) {
1051 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1052 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1053 }
1054
1055 // If an exception has been installed we must check for a pending deoptimization
1056 // Deoptimize frame if exception has been thrown.
1057
1058 if (thread()->has_pending_exception() ) {
1059 RegisterMap map(thread(), true);
1060 frame caller_fr = stub_fr.sender(&map);
1061 if (caller_fr.is_deoptimized_frame()) {
1062 // The exception patch will destroy registers that are still
1063 // live and will be needed during deoptimization. Defer the
1064 // Async exception should have deferred the exception until the
1065 // next safepoint which will be detected when we get into
1066 // the interpreter so if we have an exception now things
1067 // are messed up.
1068
1069 fatal("Exception installed and deoptimization is pending");
1070 }
1071 }
1072 }
1073 }
1074
1075
1076 //
1077 // Statistics & Instrumentations
1078 //
1079 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1080 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1081 int SafepointSynchronize::_cur_stat_index = 0;
1082 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1083 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1084 jlong SafepointSynchronize::_max_sync_time = 0;
1085 jlong SafepointSynchronize::_max_vmop_time = 0;
1086 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1087
1088 static jlong cleanup_end_time = 0;
1089 static bool need_to_track_page_armed_status = false;
1090 static bool init_done = false;
1091
1092 // Helper method to print the header.
1093 static void print_header() {
1094 tty->print(" vmop "
1095 "[threads: total initially_running wait_to_block] ");
1096 tty->print("[time: spin block sync cleanup vmop] ");
1097
1098 // no page armed status printed out if it is always armed.
1099 if (need_to_track_page_armed_status) {
1100 tty->print("page_armed ");
1101 }
1102
1103 tty->print_cr("page_trap_count");
1104 }
1105
1106 void SafepointSynchronize::deferred_initialize_stat() {
1107 if (init_done) return;
1108
1109 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1110 // be printed right away, in which case, _safepoint_stats will regress to
1111 // a single element array. Otherwise, it is a circular ring buffer with default
1112 // size of PrintSafepointStatisticsCount.
1113 int stats_array_size;
1114 if (PrintSafepointStatisticsTimeout > 0) {
1115 stats_array_size = 1;
1116 PrintSafepointStatistics = true;
1117 } else {
1118 stats_array_size = PrintSafepointStatisticsCount;
1119 }
1120 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1121 * sizeof(SafepointStats), mtInternal);
1122 guarantee(_safepoint_stats != NULL,
1123 "not enough memory for safepoint instrumentation data");
1124
1125 if (DeferPollingPageLoopCount >= 0) {
1126 need_to_track_page_armed_status = true;
1127 }
1128 init_done = true;
1129 }
1130
1131 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1132 assert(init_done, "safepoint statistics array hasn't been initialized");
1133 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1134
1135 spstat->_time_stamp = _ts_of_current_safepoint;
1136
1137 VM_Operation *op = VMThread::vm_operation();
1138 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1139 if (op != NULL) {
1140 _safepoint_reasons[spstat->_vmop_type]++;
1141 }
1142
1143 spstat->_nof_total_threads = nof_threads;
1144 spstat->_nof_initial_running_threads = nof_running;
1145 spstat->_nof_threads_hit_page_trap = 0;
1146
1147 // Records the start time of spinning. The real time spent on spinning
1148 // will be adjusted when spin is done. Same trick is applied for time
1149 // spent on waiting for threads to block.
1150 if (nof_running != 0) {
1151 spstat->_time_to_spin = os::javaTimeNanos();
1152 } else {
1153 spstat->_time_to_spin = 0;
1154 }
1155 }
1156
1157 void SafepointSynchronize::update_statistics_on_spin_end() {
1158 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1159
1160 jlong cur_time = os::javaTimeNanos();
1161
1162 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1163 if (spstat->_nof_initial_running_threads != 0) {
1164 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1165 }
1166
1167 if (need_to_track_page_armed_status) {
1168 spstat->_page_armed = (PageArmed == 1);
1169 }
1170
1171 // Records the start time of waiting for to block. Updated when block is done.
1172 if (_waiting_to_block != 0) {
1173 spstat->_time_to_wait_to_block = cur_time;
1174 } else {
1175 spstat->_time_to_wait_to_block = 0;
1176 }
1177 }
1178
1179 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1180 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1181
1182 if (spstat->_nof_threads_wait_to_block != 0) {
1183 spstat->_time_to_wait_to_block = end_time -
1184 spstat->_time_to_wait_to_block;
1185 }
1186
1187 // Records the end time of sync which will be used to calculate the total
1188 // vm operation time. Again, the real time spending in syncing will be deducted
1189 // from the start of the sync time later when end_statistics is called.
1190 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1191 if (spstat->_time_to_sync > _max_sync_time) {
1192 _max_sync_time = spstat->_time_to_sync;
1193 }
1194
1195 spstat->_time_to_do_cleanups = end_time;
1196 }
1197
1198 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1199 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1200
1201 // Record how long spent in cleanup tasks.
1202 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1203
1204 cleanup_end_time = end_time;
1205 }
1206
1207 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1208 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1209
1210 // Update the vm operation time.
1211 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1212 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1213 _max_vmop_time = spstat->_time_to_exec_vmop;
1214 }
1215 // Only the sync time longer than the specified
1216 // PrintSafepointStatisticsTimeout will be printed out right away.
1217 // By default, it is -1 meaning all samples will be put into the list.
1218 if ( PrintSafepointStatisticsTimeout > 0) {
1219 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1220 print_statistics();
1221 }
1222 } else {
1223 // The safepoint statistics will be printed out when the _safepoin_stats
1224 // array fills up.
1225 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1226 print_statistics();
1227 _cur_stat_index = 0;
1228 } else {
1229 _cur_stat_index++;
1230 }
1231 }
1232 }
1233
1234 void SafepointSynchronize::print_statistics() {
1235 SafepointStats* sstats = _safepoint_stats;
1236
1237 for (int index = 0; index <= _cur_stat_index; index++) {
1238 if (index % 30 == 0) {
1239 print_header();
1240 }
1241 sstats = &_safepoint_stats[index];
1242 tty->print("%.3f: ", sstats->_time_stamp);
1243 tty->print("%-26s ["
1244 INT32_FORMAT_W(8) INT32_FORMAT_W(11) INT32_FORMAT_W(15)
1245 " ] ",
1246 sstats->_vmop_type == -1 ? "no vm operation" :
1247 VM_Operation::name(sstats->_vmop_type),
1248 sstats->_nof_total_threads,
1249 sstats->_nof_initial_running_threads,
1250 sstats->_nof_threads_wait_to_block);
1251 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1252 tty->print(" ["
1253 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1254 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1255 INT64_FORMAT_W(6) " ] ",
1256 sstats->_time_to_spin / MICROUNITS,
1257 sstats->_time_to_wait_to_block / MICROUNITS,
1258 sstats->_time_to_sync / MICROUNITS,
1259 sstats->_time_to_do_cleanups / MICROUNITS,
1260 sstats->_time_to_exec_vmop / MICROUNITS);
1261
1262 if (need_to_track_page_armed_status) {
1263 tty->print(INT32_FORMAT " ", sstats->_page_armed);
1264 }
1265 tty->print_cr(INT32_FORMAT " ", sstats->_nof_threads_hit_page_trap);
1266 }
1267 }
1268
1269 // This method will be called when VM exits. It will first call
1270 // print_statistics to print out the rest of the sampling. Then
1271 // it tries to summarize the sampling.
1272 void SafepointSynchronize::print_stat_on_exit() {
1273 if (_safepoint_stats == NULL) return;
1274
1275 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1276
1277 // During VM exit, end_statistics may not get called and in that
1278 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1279 // don't print it out.
1280 // Approximate the vm op time.
1281 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1282 os::javaTimeNanos() - cleanup_end_time;
1283
1284 if ( PrintSafepointStatisticsTimeout < 0 ||
1285 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1286 print_statistics();
1287 }
1288 tty->cr();
1289
1290 // Print out polling page sampling status.
1291 if (!need_to_track_page_armed_status) {
1292 tty->print_cr("Polling page always armed");
1293 } else {
1294 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
1295 DeferPollingPageLoopCount);
1296 }
1297
1298 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1299 if (_safepoint_reasons[index] != 0) {
1300 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1301 _safepoint_reasons[index]);
1302 }
1303 }
1304
1305 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1306 _coalesced_vmop_count);
1307 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1308 _max_sync_time / MICROUNITS);
1309 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1310 INT64_FORMAT_W(5) " ms",
1311 _max_vmop_time / MICROUNITS);
1312 }
1313
1314 // ------------------------------------------------------------------------------------------------
1315 // Non-product code
1316
1317 #ifndef PRODUCT
1318
1319 void SafepointSynchronize::print_state() {
1320 if (_state == _not_synchronized) {
1321 tty->print_cr("not synchronized");
1322 } else if (_state == _synchronizing || _state == _synchronized) {
1323 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1324 "synchronized");
1325
1326 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1327 cur->safepoint_state()->print();
1328 }
1329 }
1330 }
1331
1332 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1333 if (ShowSafepointMsgs) {
1334 va_list ap;
1335 va_start(ap, format);
1336 tty->vprint_cr(format, ap);
1337 va_end(ap);
1338 }
1339 }
1340
1341 #endif // !PRODUCT