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/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.inline.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 "services/runtimeService.hpp"
58 #include "utilities/events.hpp"
59 #include "utilities/macros.hpp"
60 #if INCLUDE_ALL_GCS
61 #include "gc/cms/concurrentMarkSweepThread.hpp"
62 #include "gc/g1/suspendibleThreadSet.hpp"
63 #endif // INCLUDE_ALL_GCS
64 #ifdef COMPILER1
65 #include "c1/c1_globals.hpp"
66 #endif
67
68 // --------------------------------------------------------------------------------------------------
69 // Implementation of Safepoint begin/end
70
71 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
72 volatile int SafepointSynchronize::_waiting_to_block = 0;
73 volatile int SafepointSynchronize::_safepoint_counter = 0;
74 int SafepointSynchronize::_current_jni_active_count = 0;
75 long SafepointSynchronize::_end_of_last_safepoint = 0;
76 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
77 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
78 static bool timeout_error_printed = false;
79
80 // Roll all threads forward to a safepoint and suspend them all
81 void SafepointSynchronize::begin() {
82
83 Thread* myThread = Thread::current();
84 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
85
86 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
87 _safepoint_begin_time = os::javaTimeNanos();
88 _ts_of_current_safepoint = tty->time_stamp().seconds();
89 }
90
91 #if INCLUDE_ALL_GCS
92 if (UseConcMarkSweepGC) {
93 // In the future we should investigate whether CMS can use the
94 // more-general mechanism below. DLD (01/05).
95 ConcurrentMarkSweepThread::synchronize(false);
96 } else if (UseG1GC) {
97 SuspendibleThreadSet::synchronize();
98 }
99 #endif // INCLUDE_ALL_GCS
100
101 // By getting the Threads_lock, we assure that no threads are about to start or
102 // exit. It is released again in SafepointSynchronize::end().
103 Threads_lock->lock();
104
105 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
106
107 int nof_threads = Threads::number_of_threads();
108
109 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads);
110
111 RuntimeService::record_safepoint_begin();
112
113 MutexLocker mu(Safepoint_lock);
114
115 // Reset the count of active JNI critical threads
116 _current_jni_active_count = 0;
117
118 // Set number of threads to wait for, before we initiate the callbacks
119 _waiting_to_block = nof_threads;
120 TryingToBlock = 0 ;
121 int still_running = nof_threads;
122
123 // Save the starting time, so that it can be compared to see if this has taken
124 // too long to complete.
125 jlong safepoint_limit_time = 0;
126 timeout_error_printed = false;
127
128 // PrintSafepointStatisticsTimeout can be specified separately. When
129 // specified, PrintSafepointStatistics will be set to true in
130 // deferred_initialize_stat method. The initialization has to be done
131 // early enough to avoid any races. See bug 6880029 for details.
132 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
133 deferred_initialize_stat();
134 }
135
136 // Begin the process of bringing the system to a safepoint.
137 // Java threads can be in several different states and are
138 // stopped by different mechanisms:
139 //
140 // 1. Running interpreted
141 // The interpreter dispatch table is changed to force it to
142 // check for a safepoint condition between bytecodes.
143 // 2. Running in native code
144 // When returning from the native code, a Java thread must check
145 // the safepoint _state to see if we must block. If the
146 // VM thread sees a Java thread in native, it does
147 // not wait for this thread to block. The order of the memory
148 // writes and reads of both the safepoint state and the Java
149 // threads state is critical. In order to guarantee that the
150 // memory writes are serialized with respect to each other,
151 // the VM thread issues a memory barrier instruction
152 // (on MP systems). In order to avoid the overhead of issuing
153 // a memory barrier for each Java thread making native calls, each Java
154 // thread performs a write to a single memory page after changing
155 // the thread state. The VM thread performs a sequence of
156 // mprotect OS calls which forces all previous writes from all
157 // Java threads to be serialized. This is done in the
158 // os::serialize_thread_states() call. This has proven to be
159 // much more efficient than executing a membar instruction
160 // on every call to native code.
161 // 3. Running compiled Code
162 // Compiled code reads a global (Safepoint Polling) page that
163 // is set to fault if we are trying to get to a safepoint.
164 // 4. Blocked
165 // A thread which is blocked will not be allowed to return from the
166 // block condition until the safepoint operation is complete.
167 // 5. In VM or Transitioning between states
168 // If a Java thread is currently running in the VM or transitioning
169 // between states, the safepointing code will wait for the thread to
170 // block itself when it attempts transitions to a new state.
171 //
172 _state = _synchronizing;
173 OrderAccess::fence();
174
175 // Flush all thread states to memory
176 if (!UseMembar) {
177 os::serialize_thread_states();
178 }
179
180 // Make interpreter safepoint aware
181 Interpreter::notice_safepoints();
182
183 if (DeferPollingPageLoopCount < 0) {
184 // Make polling safepoint aware
185 guarantee (PageArmed == 0, "invariant") ;
186 PageArmed = 1 ;
187 os::make_polling_page_unreadable();
188 }
189
190 // Consider using active_processor_count() ... but that call is expensive.
191 int ncpus = os::processor_count() ;
192
193 #ifdef ASSERT
194 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
195 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
196 // Clear the visited flag to ensure that the critical counts are collected properly.
197 cur->set_visited_for_critical_count(false);
198 }
199 #endif // ASSERT
200
201 if (SafepointTimeout)
202 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
203
204 // Iterate through all threads until it have been determined how to stop them all at a safepoint
205 unsigned int iterations = 0;
206 int steps = 0 ;
207 while(still_running > 0) {
208 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
209 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
210 ThreadSafepointState *cur_state = cur->safepoint_state();
211 if (cur_state->is_running()) {
212 cur_state->examine_state_of_thread();
213 if (!cur_state->is_running()) {
214 still_running--;
215 // consider adjusting steps downward:
216 // steps = 0
217 // steps -= NNN
218 // steps >>= 1
219 // steps = MIN(steps, 2000-100)
220 // if (iterations != 0) steps -= NNN
221 }
222 if (log_is_enabled(Trace, safepoint)) {
223 ResourceMark rm;
224 cur_state->print_on(LogHandle(safepoint)::debug_stream());
225 }
226 }
227 }
228
229 if (PrintSafepointStatistics && iterations == 0) {
230 begin_statistics(nof_threads, still_running);
231 }
232
233 if (still_running > 0) {
234 // Check for if it takes to long
235 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
236 print_safepoint_timeout(_spinning_timeout);
237 }
238
239 // Spin to avoid context switching.
240 // There's a tension between allowing the mutators to run (and rendezvous)
241 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
242 // a mutator might otherwise use profitably to reach a safepoint. Excessive
243 // spinning by the VM thread on a saturated system can increase rendezvous latency.
244 // Blocking or yielding incur their own penalties in the form of context switching
245 // and the resultant loss of $ residency.
246 //
247 // Further complicating matters is that yield() does not work as naively expected
248 // on many platforms -- yield() does not guarantee that any other ready threads
249 // will run. As such we revert to naked_short_sleep() after some number of iterations.
250 // nakes_short_sleep() is implemented as a short unconditional sleep.
251 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
252 // can actually increase the time it takes the VM thread to detect that a system-wide
253 // stop-the-world safepoint has been reached. In a pathological scenario such as that
254 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
255 // In that case the mutators will be stalled waiting for the safepoint to complete and the
256 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
257 // will eventually wake up and detect that all mutators are safe, at which point
258 // we'll again make progress.
259 //
260 // Beware too that that the VMThread typically runs at elevated priority.
261 // Its default priority is higher than the default mutator priority.
262 // Obviously, this complicates spinning.
263 //
264 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
265 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
266 //
267 // See the comments in synchronizer.cpp for additional remarks on spinning.
268 //
269 // In the future we might:
270 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
271 // This is tricky as the path used by a thread exiting the JVM (say on
272 // on JNI call-out) simply stores into its state field. The burden
273 // is placed on the VM thread, which must poll (spin).
274 // 2. Find something useful to do while spinning. If the safepoint is GC-related
275 // we might aggressively scan the stacks of threads that are already safe.
276 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
277 // If all the mutators are ONPROC there's no reason to sleep or yield.
278 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
279 // 5. Check system saturation. If the system is not fully saturated then
280 // simply spin and avoid sleep/yield.
281 // 6. As still-running mutators rendezvous they could unpark the sleeping
282 // VMthread. This works well for still-running mutators that become
283 // safe. The VMthread must still poll for mutators that call-out.
284 // 7. Drive the policy on time-since-begin instead of iterations.
285 // 8. Consider making the spin duration a function of the # of CPUs:
286 // Spin = (((ncpus-1) * M) + K) + F(still_running)
287 // Alternately, instead of counting iterations of the outer loop
288 // we could count the # of threads visited in the inner loop, above.
289 // 9. On windows consider using the return value from SwitchThreadTo()
290 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
291
292 if (int(iterations) == DeferPollingPageLoopCount) {
293 guarantee (PageArmed == 0, "invariant") ;
294 PageArmed = 1 ;
295 os::make_polling_page_unreadable();
296 }
297
298 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
299 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
300 ++steps ;
301 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
302 SpinPause() ; // MP-Polite spin
303 } else
304 if (steps < DeferThrSuspendLoopCount) {
305 os::naked_yield() ;
306 } else {
307 os::naked_short_sleep(1);
308 }
309
310 iterations ++ ;
311 }
312 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
313 }
314 assert(still_running == 0, "sanity check");
315
316 if (PrintSafepointStatistics) {
317 update_statistics_on_spin_end();
318 }
319
320 // wait until all threads are stopped
321 while (_waiting_to_block > 0) {
322 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
323 if (!SafepointTimeout || timeout_error_printed) {
324 Safepoint_lock->wait(true); // true, means with no safepoint checks
325 } else {
326 // Compute remaining time
327 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
328
329 // If there is no remaining time, then there is an error
330 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
331 print_safepoint_timeout(_blocking_timeout);
332 }
333 }
334 }
335 assert(_waiting_to_block == 0, "sanity check");
336
337 #ifndef PRODUCT
338 if (SafepointTimeout) {
339 jlong current_time = os::javaTimeNanos();
340 if (safepoint_limit_time < current_time) {
341 tty->print_cr("# SafepointSynchronize: Finished after "
342 INT64_FORMAT_W(6) " ms",
343 ((current_time - safepoint_limit_time) / MICROUNITS +
344 (jlong)SafepointTimeoutDelay));
345 }
346 }
347 #endif
348
349 assert((_safepoint_counter & 0x1) == 0, "must be even");
350 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
351 _safepoint_counter ++;
352
353 // Record state
354 _state = _synchronized;
355
356 OrderAccess::fence();
357
358 #ifdef ASSERT
359 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
360 // make sure all the threads were visited
361 assert(cur->was_visited_for_critical_count(), "missed a thread");
362 }
363 #endif // ASSERT
364
365 // Update the count of active JNI critical regions
366 GC_locker::set_jni_lock_count(_current_jni_active_count);
367
368 if (log_is_enabled(Debug, safepoint)) {
369 VM_Operation *op = VMThread::vm_operation();
370 log_debug(safepoint)("Entering safepoint region: %s",
371 (op != NULL) ? op->name() : "no vm operation");
372 }
373
374 RuntimeService::record_safepoint_synchronized();
375 if (PrintSafepointStatistics) {
376 update_statistics_on_sync_end(os::javaTimeNanos());
377 }
378
379 // Call stuff that needs to be run when a safepoint is just about to be completed
380 do_cleanup_tasks();
381
382 if (PrintSafepointStatistics) {
383 // Record how much time spend on the above cleanup tasks
384 update_statistics_on_cleanup_end(os::javaTimeNanos());
385 }
386 }
387
388 // Wake up all threads, so they are ready to resume execution after the safepoint
389 // operation has been carried out
390 void SafepointSynchronize::end() {
391
392 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
393 assert((_safepoint_counter & 0x1) == 1, "must be odd");
394 _safepoint_counter ++;
395 // memory fence isn't required here since an odd _safepoint_counter
396 // value can do no harm and a fence is issued below anyway.
397
398 DEBUG_ONLY(Thread* myThread = Thread::current();)
399 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
400
401 if (PrintSafepointStatistics) {
402 end_statistics(os::javaTimeNanos());
403 }
404
405 #ifdef ASSERT
406 // A pending_exception cannot be installed during a safepoint. The threads
407 // may install an async exception after they come back from a safepoint into
408 // pending_exception after they unblock. But that should happen later.
409 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
410 assert (!(cur->has_pending_exception() &&
411 cur->safepoint_state()->is_at_poll_safepoint()),
412 "safepoint installed a pending exception");
413 }
414 #endif // ASSERT
415
416 if (PageArmed) {
417 // Make polling safepoint aware
418 os::make_polling_page_readable();
419 PageArmed = 0 ;
420 }
421
422 // Remove safepoint check from interpreter
423 Interpreter::ignore_safepoints();
424
425 {
426 MutexLocker mu(Safepoint_lock);
427
428 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
429
430 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
431 // when they get restarted.
432 _state = _not_synchronized;
433 OrderAccess::fence();
434
435 log_debug(safepoint)("Leaving safepoint region");
436
437 // Start suspended threads
438 for(JavaThread *current = Threads::first(); current; current = current->next()) {
439 // A problem occurring on Solaris is when attempting to restart threads
440 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
441 // to the next one (since it has been running the longest). We then have
442 // to wait for a cpu to become available before we can continue restarting
443 // threads.
444 // FIXME: This causes the performance of the VM to degrade when active and with
445 // large numbers of threads. Apparently this is due to the synchronous nature
446 // of suspending threads.
447 //
448 // TODO-FIXME: the comments above are vestigial and no longer apply.
449 // Furthermore, using solaris' schedctl in this particular context confers no benefit
450 if (VMThreadHintNoPreempt) {
451 os::hint_no_preempt();
452 }
453 ThreadSafepointState* cur_state = current->safepoint_state();
454 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
455 cur_state->restart();
456 assert(cur_state->is_running(), "safepoint state has not been reset");
457 }
458
459 RuntimeService::record_safepoint_end();
460
461 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
462 // blocked in signal_thread_blocked
463 Threads_lock->unlock();
464
465 }
466 #if INCLUDE_ALL_GCS
467 // If there are any concurrent GC threads resume them.
468 if (UseConcMarkSweepGC) {
469 ConcurrentMarkSweepThread::desynchronize(false);
470 } else if (UseG1GC) {
471 SuspendibleThreadSet::desynchronize();
472 }
473 #endif // INCLUDE_ALL_GCS
474 // record this time so VMThread can keep track how much time has elapsed
475 // since last safepoint.
476 _end_of_last_safepoint = os::javaTimeMillis();
477 }
478
479 bool SafepointSynchronize::is_cleanup_needed() {
480 // Need a safepoint if some inline cache buffers is non-empty
481 if (!InlineCacheBuffer::is_empty()) return true;
482 return false;
483 }
484
485
486
487 // Various cleaning tasks that should be done periodically at safepoints
488 void SafepointSynchronize::do_cleanup_tasks() {
489 {
490 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime);
491 ObjectSynchronizer::deflate_idle_monitors();
492 }
493
494 {
495 TraceTime t2("updating inline caches", TraceSafepointCleanupTime);
496 InlineCacheBuffer::update_inline_caches();
497 }
498 {
499 TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime);
500 CompilationPolicy::policy()->do_safepoint_work();
501 }
502
503 {
504 TraceTime t4("mark nmethods", TraceSafepointCleanupTime);
505 NMethodSweeper::mark_active_nmethods();
506 }
507
508 if (SymbolTable::needs_rehashing()) {
509 TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime);
510 SymbolTable::rehash_table();
511 }
512
513 if (StringTable::needs_rehashing()) {
514 TraceTime t6("rehashing string table", TraceSafepointCleanupTime);
515 StringTable::rehash_table();
516 }
517
518 // rotate log files?
519 if (UseGCLogFileRotation) {
520 gclog_or_tty->rotate_log(false);
521 }
522
523 {
524 // CMS delays purging the CLDG until the beginning of the next safepoint and to
525 // make sure concurrent sweep is done
526 TraceTime t7("purging class loader data graph", TraceSafepointCleanupTime);
527 ClassLoaderDataGraph::purge_if_needed();
528 }
529 }
530
531
532 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
533 switch(state) {
534 case _thread_in_native:
535 // native threads are safe if they have no java stack or have walkable stack
536 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
537
538 // blocked threads should have already have walkable stack
539 case _thread_blocked:
540 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
541 return true;
542
543 default:
544 return false;
545 }
546 }
547
548
549 // See if the thread is running inside a lazy critical native and
550 // update the thread critical count if so. Also set a suspend flag to
551 // cause the native wrapper to return into the JVM to do the unlock
552 // once the native finishes.
553 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
554 if (state == _thread_in_native &&
555 thread->has_last_Java_frame() &&
556 thread->frame_anchor()->walkable()) {
557 // This thread might be in a critical native nmethod so look at
558 // the top of the stack and increment the critical count if it
559 // is.
560 frame wrapper_frame = thread->last_frame();
561 CodeBlob* stub_cb = wrapper_frame.cb();
562 if (stub_cb != NULL &&
563 stub_cb->is_nmethod() &&
564 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
565 // A thread could potentially be in a critical native across
566 // more than one safepoint, so only update the critical state on
567 // the first one. When it returns it will perform the unlock.
568 if (!thread->do_critical_native_unlock()) {
569 #ifdef ASSERT
570 if (!thread->in_critical()) {
571 GC_locker::increment_debug_jni_lock_count();
572 }
573 #endif
574 thread->enter_critical();
575 // Make sure the native wrapper calls back on return to
576 // perform the needed critical unlock.
577 thread->set_critical_native_unlock();
578 }
579 }
580 }
581 }
582
583
584
585 // -------------------------------------------------------------------------------------------------------
586 // Implementation of Safepoint callback point
587
588 void SafepointSynchronize::block(JavaThread *thread) {
589 assert(thread != NULL, "thread must be set");
590 assert(thread->is_Java_thread(), "not a Java thread");
591
592 // Threads shouldn't block if they are in the middle of printing, but...
593 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
594
595 // Only bail from the block() call if the thread is gone from the
596 // thread list; starting to exit should still block.
597 if (thread->is_terminated()) {
598 // block current thread if we come here from native code when VM is gone
599 thread->block_if_vm_exited();
600
601 // otherwise do nothing
602 return;
603 }
604
605 JavaThreadState state = thread->thread_state();
606 thread->frame_anchor()->make_walkable(thread);
607
608 // Check that we have a valid thread_state at this point
609 switch(state) {
610 case _thread_in_vm_trans:
611 case _thread_in_Java: // From compiled code
612
613 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
614 // we pretend we are still in the VM.
615 thread->set_thread_state(_thread_in_vm);
616
617 if (is_synchronizing()) {
618 Atomic::inc (&TryingToBlock) ;
619 }
620
621 // We will always be holding the Safepoint_lock when we are examine the state
622 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
623 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
624 Safepoint_lock->lock_without_safepoint_check();
625 if (is_synchronizing()) {
626 // Decrement the number of threads to wait for and signal vm thread
627 assert(_waiting_to_block > 0, "sanity check");
628 _waiting_to_block--;
629 thread->safepoint_state()->set_has_called_back(true);
630
631 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
632 if (thread->in_critical()) {
633 // Notice that this thread is in a critical section
634 increment_jni_active_count();
635 }
636
637 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
638 if (_waiting_to_block == 0) {
639 Safepoint_lock->notify_all();
640 }
641 }
642
643 // We transition the thread to state _thread_blocked here, but
644 // we can't do our usual check for external suspension and then
645 // self-suspend after the lock_without_safepoint_check() call
646 // below because we are often called during transitions while
647 // we hold different locks. That would leave us suspended while
648 // holding a resource which results in deadlocks.
649 thread->set_thread_state(_thread_blocked);
650 Safepoint_lock->unlock();
651
652 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
653 // the entire safepoint, the threads will all line up here during the safepoint.
654 Threads_lock->lock_without_safepoint_check();
655 // restore original state. This is important if the thread comes from compiled code, so it
656 // will continue to execute with the _thread_in_Java state.
657 thread->set_thread_state(state);
658 Threads_lock->unlock();
659 break;
660
661 case _thread_in_native_trans:
662 case _thread_blocked_trans:
663 case _thread_new_trans:
664 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
665 thread->print_thread_state();
666 fatal("Deadlock in safepoint code. "
667 "Should have called back to the VM before blocking.");
668 }
669
670 // We transition the thread to state _thread_blocked here, but
671 // we can't do our usual check for external suspension and then
672 // self-suspend after the lock_without_safepoint_check() call
673 // below because we are often called during transitions while
674 // we hold different locks. That would leave us suspended while
675 // holding a resource which results in deadlocks.
676 thread->set_thread_state(_thread_blocked);
677
678 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
679 // the safepoint code might still be waiting for it to block. We need to change the state here,
680 // so it can see that it is at a safepoint.
681
682 // Block until the safepoint operation is completed.
683 Threads_lock->lock_without_safepoint_check();
684
685 // Restore state
686 thread->set_thread_state(state);
687
688 Threads_lock->unlock();
689 break;
690
691 default:
692 fatal("Illegal threadstate encountered: %d", state);
693 }
694
695 // Check for pending. async. exceptions or suspends - except if the
696 // thread was blocked inside the VM. has_special_runtime_exit_condition()
697 // is called last since it grabs a lock and we only want to do that when
698 // we must.
699 //
700 // Note: we never deliver an async exception at a polling point as the
701 // compiler may not have an exception handler for it. The polling
702 // code will notice the async and deoptimize and the exception will
703 // be delivered. (Polling at a return point is ok though). Sure is
704 // a lot of bother for a deprecated feature...
705 //
706 // We don't deliver an async exception if the thread state is
707 // _thread_in_native_trans so JNI functions won't be called with
708 // a surprising pending exception. If the thread state is going back to java,
709 // async exception is checked in check_special_condition_for_native_trans().
710
711 if (state != _thread_blocked_trans &&
712 state != _thread_in_vm_trans &&
713 thread->has_special_runtime_exit_condition()) {
714 thread->handle_special_runtime_exit_condition(
715 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
716 }
717 }
718
719 // ------------------------------------------------------------------------------------------------------
720 // Exception handlers
721
722
723 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
724 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
725 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
726 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
727
728 if (ShowSafepointMsgs) {
729 tty->print("handle_polling_page_exception: ");
730 }
731
732 if (PrintSafepointStatistics) {
733 inc_page_trap_count();
734 }
735
736 ThreadSafepointState* state = thread->safepoint_state();
737
738 state->handle_polling_page_exception();
739 }
740
741
742 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
743 if (!timeout_error_printed) {
744 timeout_error_printed = true;
745 // Print out the thread info which didn't reach the safepoint for debugging
746 // purposes (useful when there are lots of threads in the debugger).
747 tty->cr();
748 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
749 if (reason == _spinning_timeout) {
750 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
751 } else if (reason == _blocking_timeout) {
752 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
753 }
754
755 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
756 ThreadSafepointState *cur_state;
757 ResourceMark rm;
758 for(JavaThread *cur_thread = Threads::first(); cur_thread;
759 cur_thread = cur_thread->next()) {
760 cur_state = cur_thread->safepoint_state();
761
762 if (cur_thread->thread_state() != _thread_blocked &&
763 ((reason == _spinning_timeout && cur_state->is_running()) ||
764 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
765 tty->print("# ");
766 cur_thread->print();
767 tty->cr();
768 }
769 }
770 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
771 }
772
773 // To debug the long safepoint, specify both DieOnSafepointTimeout &
774 // ShowMessageBoxOnError.
775 if (DieOnSafepointTimeout) {
776 VM_Operation *op = VMThread::vm_operation();
777 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
778 SafepointTimeoutDelay,
779 op != NULL ? op->name() : "no vm operation");
780 }
781 }
782
783
784 // -------------------------------------------------------------------------------------------------------
785 // Implementation of ThreadSafepointState
786
787 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
788 _thread = thread;
789 _type = _running;
790 _has_called_back = false;
791 _at_poll_safepoint = false;
792 }
793
794 void ThreadSafepointState::create(JavaThread *thread) {
795 ThreadSafepointState *state = new ThreadSafepointState(thread);
796 thread->set_safepoint_state(state);
797 }
798
799 void ThreadSafepointState::destroy(JavaThread *thread) {
800 if (thread->safepoint_state()) {
801 delete(thread->safepoint_state());
802 thread->set_safepoint_state(NULL);
803 }
804 }
805
806 void ThreadSafepointState::examine_state_of_thread() {
807 assert(is_running(), "better be running or just have hit safepoint poll");
808
809 JavaThreadState state = _thread->thread_state();
810
811 // Save the state at the start of safepoint processing.
812 _orig_thread_state = state;
813
814 // Check for a thread that is suspended. Note that thread resume tries
815 // to grab the Threads_lock which we own here, so a thread cannot be
816 // resumed during safepoint synchronization.
817
818 // We check to see if this thread is suspended without locking to
819 // avoid deadlocking with a third thread that is waiting for this
820 // thread to be suspended. The third thread can notice the safepoint
821 // that we're trying to start at the beginning of its SR_lock->wait()
822 // call. If that happens, then the third thread will block on the
823 // safepoint while still holding the underlying SR_lock. We won't be
824 // able to get the SR_lock and we'll deadlock.
825 //
826 // We don't need to grab the SR_lock here for two reasons:
827 // 1) The suspend flags are both volatile and are set with an
828 // Atomic::cmpxchg() call so we should see the suspended
829 // state right away.
830 // 2) We're being called from the safepoint polling loop; if
831 // we don't see the suspended state on this iteration, then
832 // we'll come around again.
833 //
834 bool is_suspended = _thread->is_ext_suspended();
835 if (is_suspended) {
836 roll_forward(_at_safepoint);
837 return;
838 }
839
840 // Some JavaThread states have an initial safepoint state of
841 // running, but are actually at a safepoint. We will happily
842 // agree and update the safepoint state here.
843 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
844 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
845 roll_forward(_at_safepoint);
846 return;
847 }
848
849 if (state == _thread_in_vm) {
850 roll_forward(_call_back);
851 return;
852 }
853
854 // All other thread states will continue to run until they
855 // transition and self-block in state _blocked
856 // Safepoint polling in compiled code causes the Java threads to do the same.
857 // Note: new threads may require a malloc so they must be allowed to finish
858
859 assert(is_running(), "examine_state_of_thread on non-running thread");
860 return;
861 }
862
863 // Returns true is thread could not be rolled forward at present position.
864 void ThreadSafepointState::roll_forward(suspend_type type) {
865 _type = type;
866
867 switch(_type) {
868 case _at_safepoint:
869 SafepointSynchronize::signal_thread_at_safepoint();
870 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
871 if (_thread->in_critical()) {
872 // Notice that this thread is in a critical section
873 SafepointSynchronize::increment_jni_active_count();
874 }
875 break;
876
877 case _call_back:
878 set_has_called_back(false);
879 break;
880
881 case _running:
882 default:
883 ShouldNotReachHere();
884 }
885 }
886
887 void ThreadSafepointState::restart() {
888 switch(type()) {
889 case _at_safepoint:
890 case _call_back:
891 break;
892
893 case _running:
894 default:
895 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
896 p2i(_thread), _type);
897 _thread->print();
898 ShouldNotReachHere();
899 }
900 _type = _running;
901 set_has_called_back(false);
902 }
903
904
905 void ThreadSafepointState::print_on(outputStream *st) const {
906 const char *s = NULL;
907
908 switch(_type) {
909 case _running : s = "_running"; break;
910 case _at_safepoint : s = "_at_safepoint"; break;
911 case _call_back : s = "_call_back"; break;
912 default:
913 ShouldNotReachHere();
914 }
915
916 st->print_cr("Thread: " INTPTR_FORMAT
917 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
918 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
919 _at_poll_safepoint);
920
921 _thread->print_thread_state_on(st);
922 }
923
924 // ---------------------------------------------------------------------------------------------------------------------
925
926 // Block the thread at the safepoint poll or poll return.
927 void ThreadSafepointState::handle_polling_page_exception() {
928
929 // Check state. block() will set thread state to thread_in_vm which will
930 // cause the safepoint state _type to become _call_back.
931 assert(type() == ThreadSafepointState::_running,
932 "polling page exception on thread not running state");
933
934 // Step 1: Find the nmethod from the return address
935 if (ShowSafepointMsgs && Verbose) {
936 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
937 }
938 address real_return_addr = thread()->saved_exception_pc();
939
940 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
941 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
942 nmethod* nm = (nmethod*)cb;
943
944 // Find frame of caller
945 frame stub_fr = thread()->last_frame();
946 CodeBlob* stub_cb = stub_fr.cb();
947 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
948 RegisterMap map(thread(), true);
949 frame caller_fr = stub_fr.sender(&map);
950
951 // Should only be poll_return or poll
952 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
953
954 // This is a poll immediately before a return. The exception handling code
955 // has already had the effect of causing the return to occur, so the execution
956 // will continue immediately after the call. In addition, the oopmap at the
957 // return point does not mark the return value as an oop (if it is), so
958 // it needs a handle here to be updated.
959 if( nm->is_at_poll_return(real_return_addr) ) {
960 // See if return type is an oop.
961 bool return_oop = nm->method()->is_returning_oop();
962 Handle return_value;
963 if (return_oop) {
964 // The oop result has been saved on the stack together with all
965 // the other registers. In order to preserve it over GCs we need
966 // to keep it in a handle.
967 oop result = caller_fr.saved_oop_result(&map);
968 assert(result == NULL || result->is_oop(), "must be oop");
969 return_value = Handle(thread(), result);
970 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
971 }
972
973 // Block the thread
974 SafepointSynchronize::block(thread());
975
976 // restore oop result, if any
977 if (return_oop) {
978 caller_fr.set_saved_oop_result(&map, return_value());
979 }
980 }
981
982 // This is a safepoint poll. Verify the return address and block.
983 else {
984 set_at_poll_safepoint(true);
985
986 // verify the blob built the "return address" correctly
987 assert(real_return_addr == caller_fr.pc(), "must match");
988
989 // Block the thread
990 SafepointSynchronize::block(thread());
991 set_at_poll_safepoint(false);
992
993 // If we have a pending async exception deoptimize the frame
994 // as otherwise we may never deliver it.
995 if (thread()->has_async_condition()) {
996 ThreadInVMfromJavaNoAsyncException __tiv(thread());
997 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
998 }
999
1000 // If an exception has been installed we must check for a pending deoptimization
1001 // Deoptimize frame if exception has been thrown.
1002
1003 if (thread()->has_pending_exception() ) {
1004 RegisterMap map(thread(), true);
1005 frame caller_fr = stub_fr.sender(&map);
1006 if (caller_fr.is_deoptimized_frame()) {
1007 // The exception patch will destroy registers that are still
1008 // live and will be needed during deoptimization. Defer the
1009 // Async exception should have deferred the exception until the
1010 // next safepoint which will be detected when we get into
1011 // the interpreter so if we have an exception now things
1012 // are messed up.
1013
1014 fatal("Exception installed and deoptimization is pending");
1015 }
1016 }
1017 }
1018 }
1019
1020
1021 //
1022 // Statistics & Instrumentations
1023 //
1024 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1025 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1026 int SafepointSynchronize::_cur_stat_index = 0;
1027 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1028 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1029 jlong SafepointSynchronize::_max_sync_time = 0;
1030 jlong SafepointSynchronize::_max_vmop_time = 0;
1031 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1032
1033 static jlong cleanup_end_time = 0;
1034 static bool need_to_track_page_armed_status = false;
1035 static bool init_done = false;
1036
1037 // Helper method to print the header.
1038 static void print_header() {
1039 tty->print(" vmop "
1040 "[threads: total initially_running wait_to_block] ");
1041 tty->print("[time: spin block sync cleanup vmop] ");
1042
1043 // no page armed status printed out if it is always armed.
1044 if (need_to_track_page_armed_status) {
1045 tty->print("page_armed ");
1046 }
1047
1048 tty->print_cr("page_trap_count");
1049 }
1050
1051 void SafepointSynchronize::deferred_initialize_stat() {
1052 if (init_done) return;
1053
1054 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1055 // be printed right away, in which case, _safepoint_stats will regress to
1056 // a single element array. Otherwise, it is a circular ring buffer with default
1057 // size of PrintSafepointStatisticsCount.
1058 int stats_array_size;
1059 if (PrintSafepointStatisticsTimeout > 0) {
1060 stats_array_size = 1;
1061 PrintSafepointStatistics = true;
1062 } else {
1063 stats_array_size = PrintSafepointStatisticsCount;
1064 }
1065 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1066 * sizeof(SafepointStats), mtInternal);
1067 guarantee(_safepoint_stats != NULL,
1068 "not enough memory for safepoint instrumentation data");
1069
1070 if (DeferPollingPageLoopCount >= 0) {
1071 need_to_track_page_armed_status = true;
1072 }
1073 init_done = true;
1074 }
1075
1076 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1077 assert(init_done, "safepoint statistics array hasn't been initialized");
1078 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1079
1080 spstat->_time_stamp = _ts_of_current_safepoint;
1081
1082 VM_Operation *op = VMThread::vm_operation();
1083 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1084 if (op != NULL) {
1085 _safepoint_reasons[spstat->_vmop_type]++;
1086 }
1087
1088 spstat->_nof_total_threads = nof_threads;
1089 spstat->_nof_initial_running_threads = nof_running;
1090 spstat->_nof_threads_hit_page_trap = 0;
1091
1092 // Records the start time of spinning. The real time spent on spinning
1093 // will be adjusted when spin is done. Same trick is applied for time
1094 // spent on waiting for threads to block.
1095 if (nof_running != 0) {
1096 spstat->_time_to_spin = os::javaTimeNanos();
1097 } else {
1098 spstat->_time_to_spin = 0;
1099 }
1100 }
1101
1102 void SafepointSynchronize::update_statistics_on_spin_end() {
1103 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1104
1105 jlong cur_time = os::javaTimeNanos();
1106
1107 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1108 if (spstat->_nof_initial_running_threads != 0) {
1109 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1110 }
1111
1112 if (need_to_track_page_armed_status) {
1113 spstat->_page_armed = (PageArmed == 1);
1114 }
1115
1116 // Records the start time of waiting for to block. Updated when block is done.
1117 if (_waiting_to_block != 0) {
1118 spstat->_time_to_wait_to_block = cur_time;
1119 } else {
1120 spstat->_time_to_wait_to_block = 0;
1121 }
1122 }
1123
1124 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1125 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1126
1127 if (spstat->_nof_threads_wait_to_block != 0) {
1128 spstat->_time_to_wait_to_block = end_time -
1129 spstat->_time_to_wait_to_block;
1130 }
1131
1132 // Records the end time of sync which will be used to calculate the total
1133 // vm operation time. Again, the real time spending in syncing will be deducted
1134 // from the start of the sync time later when end_statistics is called.
1135 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1136 if (spstat->_time_to_sync > _max_sync_time) {
1137 _max_sync_time = spstat->_time_to_sync;
1138 }
1139
1140 spstat->_time_to_do_cleanups = end_time;
1141 }
1142
1143 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1144 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1145
1146 // Record how long spent in cleanup tasks.
1147 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1148
1149 cleanup_end_time = end_time;
1150 }
1151
1152 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1153 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1154
1155 // Update the vm operation time.
1156 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1157 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1158 _max_vmop_time = spstat->_time_to_exec_vmop;
1159 }
1160 // Only the sync time longer than the specified
1161 // PrintSafepointStatisticsTimeout will be printed out right away.
1162 // By default, it is -1 meaning all samples will be put into the list.
1163 if ( PrintSafepointStatisticsTimeout > 0) {
1164 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1165 print_statistics();
1166 }
1167 } else {
1168 // The safepoint statistics will be printed out when the _safepoin_stats
1169 // array fills up.
1170 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1171 print_statistics();
1172 _cur_stat_index = 0;
1173 } else {
1174 _cur_stat_index++;
1175 }
1176 }
1177 }
1178
1179 void SafepointSynchronize::print_statistics() {
1180 SafepointStats* sstats = _safepoint_stats;
1181
1182 for (int index = 0; index <= _cur_stat_index; index++) {
1183 if (index % 30 == 0) {
1184 print_header();
1185 }
1186 sstats = &_safepoint_stats[index];
1187 tty->print("%.3f: ", sstats->_time_stamp);
1188 tty->print("%-26s ["
1189 INT32_FORMAT_W(8) INT32_FORMAT_W(11) INT32_FORMAT_W(15)
1190 " ] ",
1191 sstats->_vmop_type == -1 ? "no vm operation" :
1192 VM_Operation::name(sstats->_vmop_type),
1193 sstats->_nof_total_threads,
1194 sstats->_nof_initial_running_threads,
1195 sstats->_nof_threads_wait_to_block);
1196 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1197 tty->print(" ["
1198 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1199 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1200 INT64_FORMAT_W(6) " ] ",
1201 sstats->_time_to_spin / MICROUNITS,
1202 sstats->_time_to_wait_to_block / MICROUNITS,
1203 sstats->_time_to_sync / MICROUNITS,
1204 sstats->_time_to_do_cleanups / MICROUNITS,
1205 sstats->_time_to_exec_vmop / MICROUNITS);
1206
1207 if (need_to_track_page_armed_status) {
1208 tty->print(INT32_FORMAT " ", sstats->_page_armed);
1209 }
1210 tty->print_cr(INT32_FORMAT " ", sstats->_nof_threads_hit_page_trap);
1211 }
1212 }
1213
1214 // This method will be called when VM exits. It will first call
1215 // print_statistics to print out the rest of the sampling. Then
1216 // it tries to summarize the sampling.
1217 void SafepointSynchronize::print_stat_on_exit() {
1218 if (_safepoint_stats == NULL) return;
1219
1220 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1221
1222 // During VM exit, end_statistics may not get called and in that
1223 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1224 // don't print it out.
1225 // Approximate the vm op time.
1226 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1227 os::javaTimeNanos() - cleanup_end_time;
1228
1229 if ( PrintSafepointStatisticsTimeout < 0 ||
1230 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1231 print_statistics();
1232 }
1233 tty->cr();
1234
1235 // Print out polling page sampling status.
1236 if (!need_to_track_page_armed_status) {
1237 tty->print_cr("Polling page always armed");
1238 } else {
1239 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
1240 DeferPollingPageLoopCount);
1241 }
1242
1243 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1244 if (_safepoint_reasons[index] != 0) {
1245 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1246 _safepoint_reasons[index]);
1247 }
1248 }
1249
1250 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1251 _coalesced_vmop_count);
1252 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1253 _max_sync_time / MICROUNITS);
1254 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1255 INT64_FORMAT_W(5) " ms",
1256 _max_vmop_time / MICROUNITS);
1257 }
1258
1259 // ------------------------------------------------------------------------------------------------
1260 // Non-product code
1261
1262 #ifndef PRODUCT
1263
1264 void SafepointSynchronize::print_state() {
1265 if (_state == _not_synchronized) {
1266 tty->print_cr("not synchronized");
1267 } else if (_state == _synchronizing || _state == _synchronized) {
1268 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1269 "synchronized");
1270
1271 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1272 cur->safepoint_state()->print();
1273 }
1274 }
1275 }
1276
1277 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1278 if (ShowSafepointMsgs) {
1279 va_list ap;
1280 va_start(ap, format);
1281 tty->vprint_cr(format, ap);
1282 va_end(ap);
1283 }
1284 }
1285
1286 #endif // !PRODUCT