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