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