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 #if INCLUDE_ALL_GCS
64 #include "gc/shenandoah/shenandoahConcurrentThread.hpp"
65 #include "gc/cms/concurrentMarkSweepThread.hpp"
66 #include "gc/g1/suspendibleThreadSet.hpp"
67 #endif // INCLUDE_ALL_GCS
68 #ifdef COMPILER1
69 #include "c1/c1_globals.hpp"
70 #endif
71
72 // --------------------------------------------------------------------------------------------------
73 // Implementation of Safepoint begin/end
74
75 WorkGang* SafepointSynchronize::_cleanup_workers = NULL;
76 SubTasksDone* SafepointSynchronize::_cleanup_subtasks = NULL;
77
78 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
79 volatile int SafepointSynchronize::_waiting_to_block = 0;
80 volatile int SafepointSynchronize::_safepoint_counter = 0;
81 int SafepointSynchronize::_current_jni_active_count = 0;
82 long SafepointSynchronize::_end_of_last_safepoint = 0;
83 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
84 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
85 static bool timeout_error_printed = false;
86
87 // Roll all threads forward to a safepoint and suspend them all
88 void SafepointSynchronize::begin() {
89 EventSafepointBegin begin_event;
90 Thread* myThread = Thread::current();
91 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
92
93 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
94 _safepoint_begin_time = os::javaTimeNanos();
95 _ts_of_current_safepoint = tty->time_stamp().seconds();
96 }
97
98 #if INCLUDE_ALL_GCS
99 if (UseConcMarkSweepGC) {
100 // In the future we should investigate whether CMS can use the
101 // more-general mechanism below. DLD (01/05).
102 ConcurrentMarkSweepThread::synchronize(false);
103 } else if (UseG1GC) {
104 SuspendibleThreadSet::synchronize();
105 }
106 #endif // INCLUDE_ALL_GCS
107
108 // By getting the Threads_lock, we assure that no threads are about to start or
109 // exit. It is released again in SafepointSynchronize::end().
110 Threads_lock->lock();
111
112 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
113
114 int nof_threads = Threads::number_of_threads();
115
116 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads);
117
118 RuntimeService::record_safepoint_begin();
119
120 MutexLocker mu(Safepoint_lock);
121
122 // Reset the count of active JNI critical threads
123 _current_jni_active_count = 0;
124
125 // Set number of threads to wait for, before we initiate the callbacks
126 _waiting_to_block = nof_threads;
127 TryingToBlock = 0 ;
128 int still_running = nof_threads;
129
130 // Save the starting time, so that it can be compared to see if this has taken
131 // too long to complete.
132 jlong safepoint_limit_time = 0;
133 timeout_error_printed = false;
134
135 // PrintSafepointStatisticsTimeout can be specified separately. When
136 // specified, PrintSafepointStatistics will be set to true in
137 // deferred_initialize_stat method. The initialization has to be done
138 // early enough to avoid any races. See bug 6880029 for details.
139 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
140 deferred_initialize_stat();
141 }
142
143 // Begin the process of bringing the system to a safepoint.
144 // Java threads can be in several different states and are
145 // stopped by different mechanisms:
146 //
147 // 1. Running interpreted
148 // The interpreter dispatch table is changed to force it to
149 // check for a safepoint condition between bytecodes.
150 // 2. Running in native code
151 // When returning from the native code, a Java thread must check
152 // the safepoint _state to see if we must block. If the
153 // VM thread sees a Java thread in native, it does
154 // not wait for this thread to block. The order of the memory
155 // writes and reads of both the safepoint state and the Java
156 // threads state is critical. In order to guarantee that the
157 // memory writes are serialized with respect to each other,
158 // the VM thread issues a memory barrier instruction
159 // (on MP systems). In order to avoid the overhead of issuing
160 // a memory barrier for each Java thread making native calls, each Java
161 // thread performs a write to a single memory page after changing
162 // the thread state. The VM thread performs a sequence of
163 // mprotect OS calls which forces all previous writes from all
164 // Java threads to be serialized. This is done in the
165 // os::serialize_thread_states() call. This has proven to be
166 // much more efficient than executing a membar instruction
167 // on every call to native code.
168 // 3. Running compiled Code
169 // Compiled code reads a global (Safepoint Polling) page that
170 // is set to fault if we are trying to get to a safepoint.
171 // 4. Blocked
172 // A thread which is blocked will not be allowed to return from the
173 // block condition until the safepoint operation is complete.
174 // 5. In VM or Transitioning between states
175 // If a Java thread is currently running in the VM or transitioning
176 // between states, the safepointing code will wait for the thread to
177 // block itself when it attempts transitions to a new state.
178 //
179 {
180 EventSafepointStateSynchronization sync_event;
181 int initial_running = 0;
182
183 _state = _synchronizing;
184 OrderAccess::fence();
185
186 // Flush all thread states to memory
187 if (!UseMembar) {
188 os::serialize_thread_states();
189 }
190
191 // Make interpreter safepoint aware
192 Interpreter::notice_safepoints();
193
194 if (DeferPollingPageLoopCount < 0) {
195 // Make polling safepoint aware
196 guarantee (PageArmed == 0, "invariant") ;
197 PageArmed = 1 ;
198 os::make_polling_page_unreadable();
199 }
200
201 // Consider using active_processor_count() ... but that call is expensive.
202 int ncpus = os::processor_count() ;
203
204 #ifdef ASSERT
205 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
206 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
207 // Clear the visited flag to ensure that the critical counts are collected properly.
208 cur->set_visited_for_critical_count(false);
209 }
210 #endif // ASSERT
211
212 if (SafepointTimeout)
213 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
214
215 // Iterate through all threads until it have been determined how to stop them all at a safepoint
216 unsigned int iterations = 0;
217 int steps = 0 ;
218 while(still_running > 0) {
219 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
220 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
221 ThreadSafepointState *cur_state = cur->safepoint_state();
222 if (cur_state->is_running()) {
223 cur_state->examine_state_of_thread();
224 if (!cur_state->is_running()) {
225 still_running--;
226 // consider adjusting steps downward:
227 // steps = 0
228 // steps -= NNN
229 // steps >>= 1
230 // steps = MIN(steps, 2000-100)
231 // if (iterations != 0) steps -= NNN
232 }
233 if (log_is_enabled(Trace, safepoint)) {
234 ResourceMark rm;
235 cur_state->print_on(Log(safepoint)::trace_stream());
236 }
237 }
238 }
239
240 if (iterations == 0) {
241 initial_running = still_running;
242 if (PrintSafepointStatistics) {
243 begin_statistics(nof_threads, still_running);
244 }
245 }
246
247 if (still_running > 0) {
248 // Check for if it takes to long
249 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
250 print_safepoint_timeout(_spinning_timeout);
251 }
252
253 // Spin to avoid context switching.
254 // There's a tension between allowing the mutators to run (and rendezvous)
255 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
256 // a mutator might otherwise use profitably to reach a safepoint. Excessive
257 // spinning by the VM thread on a saturated system can increase rendezvous latency.
258 // Blocking or yielding incur their own penalties in the form of context switching
259 // and the resultant loss of $ residency.
260 //
261 // Further complicating matters is that yield() does not work as naively expected
262 // on many platforms -- yield() does not guarantee that any other ready threads
263 // will run. As such we revert to naked_short_sleep() after some number of iterations.
264 // nakes_short_sleep() is implemented as a short unconditional sleep.
265 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
266 // can actually increase the time it takes the VM thread to detect that a system-wide
267 // stop-the-world safepoint has been reached. In a pathological scenario such as that
268 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
269 // In that case the mutators will be stalled waiting for the safepoint to complete and the
270 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
271 // will eventually wake up and detect that all mutators are safe, at which point
272 // we'll again make progress.
273 //
274 // Beware too that that the VMThread typically runs at elevated priority.
275 // Its default priority is higher than the default mutator priority.
276 // Obviously, this complicates spinning.
277 //
278 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
279 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
280 //
281 // See the comments in synchronizer.cpp for additional remarks on spinning.
282 //
283 // In the future we might:
284 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
285 // This is tricky as the path used by a thread exiting the JVM (say on
286 // on JNI call-out) simply stores into its state field. The burden
287 // is placed on the VM thread, which must poll (spin).
288 // 2. Find something useful to do while spinning. If the safepoint is GC-related
289 // we might aggressively scan the stacks of threads that are already safe.
290 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
291 // If all the mutators are ONPROC there's no reason to sleep or yield.
292 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
293 // 5. Check system saturation. If the system is not fully saturated then
294 // simply spin and avoid sleep/yield.
295 // 6. As still-running mutators rendezvous they could unpark the sleeping
296 // VMthread. This works well for still-running mutators that become
297 // safe. The VMthread must still poll for mutators that call-out.
298 // 7. Drive the policy on time-since-begin instead of iterations.
299 // 8. Consider making the spin duration a function of the # of CPUs:
300 // Spin = (((ncpus-1) * M) + K) + F(still_running)
301 // Alternately, instead of counting iterations of the outer loop
302 // we could count the # of threads visited in the inner loop, above.
303 // 9. On windows consider using the return value from SwitchThreadTo()
304 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
305
306 if (int(iterations) == DeferPollingPageLoopCount) {
307 guarantee (PageArmed == 0, "invariant") ;
308 PageArmed = 1 ;
309 os::make_polling_page_unreadable();
310 }
311
312 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
313 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
314 ++steps ;
315 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
316 SpinPause() ; // MP-Polite spin
317 } else
318 if (steps < DeferThrSuspendLoopCount) {
319 os::naked_yield() ;
320 } else {
321 os::naked_short_sleep(1);
322 }
323
324 iterations ++ ;
325 }
326 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
327 }
328 assert(still_running == 0, "sanity check");
329
330 if (PrintSafepointStatistics) {
331 update_statistics_on_spin_end();
332 }
333
334 if (sync_event.should_commit()) {
335 sync_event.set_safepointId(safepoint_counter());
336 sync_event.set_initialThreadCount(initial_running);
337 sync_event.set_runningThreadCount(_waiting_to_block);
338 sync_event.set_iterations(iterations);
339 sync_event.commit();
340 }
341 } //EventSafepointStateSync
342
343 // wait until all threads are stopped
344 {
345 EventSafepointWaitBlocked wait_blocked_event;
346 int initial_waiting_to_block = _waiting_to_block;
347
348 while (_waiting_to_block > 0) {
349 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
350 if (!SafepointTimeout || timeout_error_printed) {
351 Safepoint_lock->wait(true); // true, means with no safepoint checks
352 } else {
353 // Compute remaining time
354 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
355
356 // If there is no remaining time, then there is an error
357 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
358 print_safepoint_timeout(_blocking_timeout);
359 }
360 }
361 }
362 assert(_waiting_to_block == 0, "sanity check");
363
364 #ifndef PRODUCT
365 if (SafepointTimeout) {
366 jlong current_time = os::javaTimeNanos();
367 if (safepoint_limit_time < current_time) {
368 tty->print_cr("# SafepointSynchronize: Finished after "
369 INT64_FORMAT_W(6) " ms",
370 ((current_time - safepoint_limit_time) / MICROUNITS +
371 (jlong)SafepointTimeoutDelay));
372 }
373 }
374 #endif
375
376 assert((_safepoint_counter & 0x1) == 0, "must be even");
377 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
378 _safepoint_counter ++;
379
380 // Record state
381 _state = _synchronized;
382
383 OrderAccess::fence();
384
385 if (wait_blocked_event.should_commit()) {
386 wait_blocked_event.set_safepointId(safepoint_counter());
387 wait_blocked_event.set_runningThreadCount(initial_waiting_to_block);
388 wait_blocked_event.commit();
389 }
390 } // EventSafepointWaitBlocked
391
392 #ifdef ASSERT
393 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
394 // make sure all the threads were visited
395 assert(cur->was_visited_for_critical_count(), "missed a thread");
396 }
397 #endif // ASSERT
398
399 // Update the count of active JNI critical regions
400 GCLocker::set_jni_lock_count(_current_jni_active_count);
401
402 if (log_is_enabled(Debug, safepoint)) {
403 VM_Operation *op = VMThread::vm_operation();
404 log_debug(safepoint)("Entering safepoint region: %s",
405 (op != NULL) ? op->name() : "no vm operation");
406 }
407
408 RuntimeService::record_safepoint_synchronized();
409 if (PrintSafepointStatistics) {
410 update_statistics_on_sync_end(os::javaTimeNanos());
411 }
412
413 // Call stuff that needs to be run when a safepoint is just about to be completed
414 {
415 EventSafepointCleanup cleanup_event;
416 do_cleanup_tasks();
417 if (cleanup_event.should_commit()) {
418 cleanup_event.set_safepointId(safepoint_counter());
419 cleanup_event.commit();
420 }
421 }
422
423 if (PrintSafepointStatistics) {
424 // Record how much time spend on the above cleanup tasks
425 update_statistics_on_cleanup_end(os::javaTimeNanos());
426 }
427 if (begin_event.should_commit()) {
428 begin_event.set_safepointId(safepoint_counter());
429 begin_event.set_totalThreadCount(nof_threads);
430 begin_event.set_jniCriticalThreadCount(_current_jni_active_count);
431 begin_event.commit();
432 }
433 }
434
435 // Wake up all threads, so they are ready to resume execution after the safepoint
436 // operation has been carried out
437 void SafepointSynchronize::end() {
438 EventSafepointEnd event;
439 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id"
440
441 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
442 assert((_safepoint_counter & 0x1) == 1, "must be odd");
443 _safepoint_counter ++;
444 // memory fence isn't required here since an odd _safepoint_counter
445 // value can do no harm and a fence is issued below anyway.
446
447 DEBUG_ONLY(Thread* myThread = Thread::current();)
448 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
449
450 if (PrintSafepointStatistics) {
451 end_statistics(os::javaTimeNanos());
452 }
453
454 #ifdef ASSERT
455 // A pending_exception cannot be installed during a safepoint. The threads
456 // may install an async exception after they come back from a safepoint into
457 // pending_exception after they unblock. But that should happen later.
458 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
459 assert (!(cur->has_pending_exception() &&
460 cur->safepoint_state()->is_at_poll_safepoint()),
461 "safepoint installed a pending exception");
462 }
463 #endif // ASSERT
464
465 if (PageArmed) {
466 // Make polling safepoint aware
467 os::make_polling_page_readable();
468 PageArmed = 0 ;
469 }
470
471 // Remove safepoint check from interpreter
472 Interpreter::ignore_safepoints();
473
474 {
475 MutexLocker mu(Safepoint_lock);
476
477 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
478
479 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
480 // when they get restarted.
481 _state = _not_synchronized;
482 OrderAccess::fence();
483
484 log_debug(safepoint)("Leaving safepoint region");
485
486 // Start suspended threads
487 for(JavaThread *current = Threads::first(); current; current = current->next()) {
488 // A problem occurring on Solaris is when attempting to restart threads
489 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
490 // to the next one (since it has been running the longest). We then have
491 // to wait for a cpu to become available before we can continue restarting
492 // threads.
493 // FIXME: This causes the performance of the VM to degrade when active and with
494 // large numbers of threads. Apparently this is due to the synchronous nature
495 // of suspending threads.
496 //
497 // TODO-FIXME: the comments above are vestigial and no longer apply.
498 // Furthermore, using solaris' schedctl in this particular context confers no benefit
499 if (VMThreadHintNoPreempt) {
500 os::hint_no_preempt();
501 }
502 ThreadSafepointState* cur_state = current->safepoint_state();
503 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
504 cur_state->restart();
505 assert(cur_state->is_running(), "safepoint state has not been reset");
506 }
507
508 RuntimeService::record_safepoint_end();
509
510 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
511 // blocked in signal_thread_blocked
512 Threads_lock->unlock();
513
514 }
515 #if INCLUDE_ALL_GCS
516 // If there are any concurrent GC threads resume them.
517 if (UseConcMarkSweepGC) {
518 ConcurrentMarkSweepThread::desynchronize(false);
519 } else if (UseG1GC) {
520 SuspendibleThreadSet::desynchronize();
521 }
522 #endif // INCLUDE_ALL_GCS
523 // record this time so VMThread can keep track how much time has elapsed
524 // since last safepoint.
525 _end_of_last_safepoint = os::javaTimeMillis();
526
527 if (event.should_commit()) {
528 event.set_safepointId(safepoint_id);
529 event.commit();
530 }
531 }
532
533 bool SafepointSynchronize::is_cleanup_needed() {
534 // Need a safepoint if some inline cache buffers is non-empty
535 if (!InlineCacheBuffer::is_empty()) return true;
536 return false;
537 }
538
539 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) {
540 if (event.should_commit()) {
541 event.set_safepointId(SafepointSynchronize::safepoint_counter());
542 event.set_name(name);
543 event.commit();
544 }
545 }
546
547 // Various cleaning tasks that should be done periodically at safepoints
548 void SafepointSynchronize::do_cleanup_tasks() {
549 VM_Operation* op = VMThread::vm_operation();
550 // If op does both deflating and nmethod marking, we don't bother firing up
551 // the workers.
552 bool op_does_cleanup = op != NULL && op->marks_nmethods() && op->deflates_idle_monitors();
553 if (ParallelSafepointCleanup && ! op_does_cleanup) {
554 parallel_cleanup();
555 } else {
556 serial_cleanup();
557 }
558 }
559
560 void SafepointSynchronize::serial_cleanup() {
561 VM_Operation* op = VMThread::vm_operation();
562 {
563 const char* name = "deflating idle monitors";
564 EventSafepointCleanupTask event;
565 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
566 ObjectSynchronizer::deflate_idle_monitors(op == NULL || ! op->deflates_idle_monitors());
567 event_safepoint_cleanup_task_commit(event, name);
568 }
569
570 {
571 const char* name = "updating inline caches";
572 EventSafepointCleanupTask event;
573 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
574 InlineCacheBuffer::update_inline_caches();
575 event_safepoint_cleanup_task_commit(event, name);
576 }
577 {
578 const char* name = "compilation policy safepoint handler";
579 EventSafepointCleanupTask event;
580 TraceTime timer("compilation policy safepoint handler", TRACETIME_LOG(Info, safepoint, cleanup));
581 CompilationPolicy::policy()->do_safepoint_work();
582 event_safepoint_cleanup_task_commit(event, name);
583 }
584
585 if (op == NULL || ! op->marks_nmethods()) {
586 const char* name = "mark nmethods";
587 EventSafepointCleanupTask event;
588 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
589 NMethodSweeper::mark_active_nmethods();
590 event_safepoint_cleanup_task_commit(event, name);
591 }
592
593 if (SymbolTable::needs_rehashing()) {
594 double start = os::elapsedTime();
595 const char* name = "rehashing symbol table";
596 EventSafepointCleanupTask event;
597 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
598 SymbolTable::rehash_table();
599 event_safepoint_cleanup_task_commit(event, name);
600 double end = os::elapsedTime();
601 tty->print_cr("vmthread took: %f ms for symbol table rehash", (end - start) * 1000.0);
602 }
603
604 if (StringTable::needs_rehashing()) {
605 const char* name = "rehashing string table";
606 EventSafepointCleanupTask event;
607 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
608 StringTable::rehash_table();
609 event_safepoint_cleanup_task_commit(event, name);
610 }
611
612 {
613 // CMS delays purging the CLDG until the beginning of the next safepoint and to
614 // make sure concurrent sweep is done
615 const char* name = "purging class loader data graph";
616 EventSafepointCleanupTask event;
617 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
618 ClassLoaderDataGraph::purge_if_needed();
619 event_safepoint_cleanup_task_commit(event, name);
620 }
621 }
622
623 class ParallelSPCleanupThreadClosure : public ThreadClosure {
624 private:
625 bool _do_deflate_idle_monitors;
626 CodeBlobClosure* _nmethod_cl;
627
628 public:
629 ParallelSPCleanupThreadClosure() {
630 VM_Operation* op = VMThread::vm_operation();
631 _do_deflate_idle_monitors = op == NULL || ! op->deflates_idle_monitors();
632 if (op == NULL || ! op->marks_nmethods()) {
633 _nmethod_cl = NMethodSweeper::prepare_mark_active_nmethods();
634 } else {
635 _nmethod_cl = NULL;
636 }
637 }
638
639 void do_thread(Thread* thread) {
640 if (_do_deflate_idle_monitors) {
641 ObjectSynchronizer::deflate_idle_monitors_and_oops_do(thread, NULL);
642 }
643 if (_nmethod_cl != NULL && thread->is_Java_thread() &&
644 ! thread->is_Code_cache_sweeper_thread()) {
645 JavaThread* jt = (JavaThread*) thread;
646 jt->nmethods_do(_nmethod_cl);
647 }
648 }
649 };
650
651 class ParallelSPCleanupTask : public AbstractGangTask {
652 private:
653 SubTasksDone* _subtasks;
654 ParallelSPCleanupThreadClosure _cleanup_threads_cl;
655 public:
656 ParallelSPCleanupTask(SubTasksDone* subtasks) :
657 AbstractGangTask("Parallel Safepoint Cleanup"),
658 _cleanup_threads_cl(ParallelSPCleanupThreadClosure()),
659 _subtasks(subtasks) {}
660
661 void work(uint worker_id) {
662 // All threads deflate monitors and mark nmethods (if necessary).
663 Threads::parallel_java_threads_do(&_cleanup_threads_cl);
664
665 if (! _subtasks->is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
666 const char* name = "deflating idle monitors";
667 EventSafepointCleanupTask event;
668 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
669 ObjectSynchronizer::deflate_idle_monitors(false);
670 event_safepoint_cleanup_task_commit(event, name);
671 }
672
673 if (! _subtasks->is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
674 const char* name = "updating inline caches";
675 EventSafepointCleanupTask event;
676 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
677 InlineCacheBuffer::update_inline_caches();
678 event_safepoint_cleanup_task_commit(event, name);
679 }
680
681 if (! _subtasks->is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
682 const char* name = "compilation policy safepoint handler";
683 EventSafepointCleanupTask event;
684 TraceTime timer("compilation policy safepoint handler", TRACETIME_LOG(Info, safepoint, cleanup));
685 CompilationPolicy::policy()->do_safepoint_work();
686 event_safepoint_cleanup_task_commit(event, name);
687 }
688
689 if (! _subtasks->is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
690 if (SymbolTable::needs_rehashing()) {
691 const char* name = "rehashing symbol table";
692 EventSafepointCleanupTask event;
693 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
694 SymbolTable::rehash_table();
695 event_safepoint_cleanup_task_commit(event, name);
696 }
697 }
698
699 if (! _subtasks->is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
700 if (StringTable::needs_rehashing()) {
701 const char* name = "rehashing string table";
702 EventSafepointCleanupTask event;
703 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
704 StringTable::rehash_table();
705 event_safepoint_cleanup_task_commit(event, name);
706 }
707 }
708
709 if (! _subtasks->is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) {
710 // CMS delays purging the CLDG until the beginning of the next safepoint and to
711 // make sure concurrent sweep is done
712 const char* name = "purging class loader data graph";
713 EventSafepointCleanupTask event;
714 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
715 ClassLoaderDataGraph::purge_if_needed();
716 event_safepoint_cleanup_task_commit(event, name);
717 }
718 _subtasks->all_tasks_completed(ParallelSafepointCleanupThreads);
719 }
720 };
721
722 void SafepointSynchronize::parallel_cleanup() {
723 // Deferred init
724 if (_cleanup_workers == NULL) {
725 _cleanup_workers = new WorkGang("Parallel Safepoint Cleanup", ParallelSafepointCleanupThreads, false, false);
726 _cleanup_workers->initialize_workers();
727 _cleanup_subtasks = new SubTasksDone(SAFEPOINT_CLEANUP_NUM_TASKS);
728 }
729
730 StrongRootsScope srs(_cleanup_workers->active_workers());
731 ParallelSPCleanupTask cleanup_task(_cleanup_subtasks);
732 _cleanup_workers->run_task(&cleanup_task);
733 }
734
735 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
736 switch(state) {
737 case _thread_in_native:
738 // native threads are safe if they have no java stack or have walkable stack
739 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
740
741 // blocked threads should have already have walkable stack
742 case _thread_blocked:
743 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
744 return true;
745
746 default:
747 return false;
748 }
749 }
750
751
752 // See if the thread is running inside a lazy critical native and
753 // update the thread critical count if so. Also set a suspend flag to
754 // cause the native wrapper to return into the JVM to do the unlock
755 // once the native finishes.
756 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
757 if (state == _thread_in_native &&
758 thread->has_last_Java_frame() &&
759 thread->frame_anchor()->walkable()) {
760 // This thread might be in a critical native nmethod so look at
761 // the top of the stack and increment the critical count if it
762 // is.
763 frame wrapper_frame = thread->last_frame();
764 CodeBlob* stub_cb = wrapper_frame.cb();
765 if (stub_cb != NULL &&
766 stub_cb->is_nmethod() &&
767 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
768 // A thread could potentially be in a critical native across
769 // more than one safepoint, so only update the critical state on
770 // the first one. When it returns it will perform the unlock.
771 if (!thread->do_critical_native_unlock()) {
772 #ifdef ASSERT
773 if (!thread->in_critical()) {
774 GCLocker::increment_debug_jni_lock_count();
775 }
776 #endif
777 thread->enter_critical();
778 // Make sure the native wrapper calls back on return to
779 // perform the needed critical unlock.
780 thread->set_critical_native_unlock();
781 }
782 }
783 }
784 }
785
786
787
788 // -------------------------------------------------------------------------------------------------------
789 // Implementation of Safepoint callback point
790
791 void SafepointSynchronize::block(JavaThread *thread) {
792 assert(thread != NULL, "thread must be set");
793 assert(thread->is_Java_thread(), "not a Java thread");
794
795 // Threads shouldn't block if they are in the middle of printing, but...
796 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
797
798 // Only bail from the block() call if the thread is gone from the
799 // thread list; starting to exit should still block.
800 if (thread->is_terminated()) {
801 // block current thread if we come here from native code when VM is gone
802 thread->block_if_vm_exited();
803
804 // otherwise do nothing
805 return;
806 }
807
808 JavaThreadState state = thread->thread_state();
809 thread->frame_anchor()->make_walkable(thread);
810
811 // Check that we have a valid thread_state at this point
812 switch(state) {
813 case _thread_in_vm_trans:
814 case _thread_in_Java: // From compiled code
815
816 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
817 // we pretend we are still in the VM.
818 thread->set_thread_state(_thread_in_vm);
819
820 if (is_synchronizing()) {
821 Atomic::inc (&TryingToBlock) ;
822 }
823
824 // We will always be holding the Safepoint_lock when we are examine the state
825 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
826 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
827 Safepoint_lock->lock_without_safepoint_check();
828 if (is_synchronizing()) {
829 // Decrement the number of threads to wait for and signal vm thread
830 assert(_waiting_to_block > 0, "sanity check");
831 _waiting_to_block--;
832 thread->safepoint_state()->set_has_called_back(true);
833
834 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
835 if (thread->in_critical()) {
836 // Notice that this thread is in a critical section
837 increment_jni_active_count();
838 }
839
840 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
841 if (_waiting_to_block == 0) {
842 Safepoint_lock->notify_all();
843 }
844 }
845
846 // We transition the thread to state _thread_blocked here, but
847 // we can't do our usual check for external suspension and then
848 // self-suspend after the lock_without_safepoint_check() call
849 // below because we are often called during transitions while
850 // we hold different locks. That would leave us suspended while
851 // holding a resource which results in deadlocks.
852 thread->set_thread_state(_thread_blocked);
853 Safepoint_lock->unlock();
854
855 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
856 // the entire safepoint, the threads will all line up here during the safepoint.
857 Threads_lock->lock_without_safepoint_check();
858 // restore original state. This is important if the thread comes from compiled code, so it
859 // will continue to execute with the _thread_in_Java state.
860 thread->set_thread_state(state);
861 Threads_lock->unlock();
862 break;
863
864 case _thread_in_native_trans:
865 case _thread_blocked_trans:
866 case _thread_new_trans:
867 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
868 thread->print_thread_state();
869 fatal("Deadlock in safepoint code. "
870 "Should have called back to the VM before blocking.");
871 }
872
873 // We transition the thread to state _thread_blocked here, but
874 // we can't do our usual check for external suspension and then
875 // self-suspend after the lock_without_safepoint_check() call
876 // below because we are often called during transitions while
877 // we hold different locks. That would leave us suspended while
878 // holding a resource which results in deadlocks.
879 thread->set_thread_state(_thread_blocked);
880
881 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
882 // the safepoint code might still be waiting for it to block. We need to change the state here,
883 // so it can see that it is at a safepoint.
884
885 // Block until the safepoint operation is completed.
886 Threads_lock->lock_without_safepoint_check();
887
888 // Restore state
889 thread->set_thread_state(state);
890
891 Threads_lock->unlock();
892 break;
893
894 default:
895 fatal("Illegal threadstate encountered: %d", state);
896 }
897
898 // Check for pending. async. exceptions or suspends - except if the
899 // thread was blocked inside the VM. has_special_runtime_exit_condition()
900 // is called last since it grabs a lock and we only want to do that when
901 // we must.
902 //
903 // Note: we never deliver an async exception at a polling point as the
904 // compiler may not have an exception handler for it. The polling
905 // code will notice the async and deoptimize and the exception will
906 // be delivered. (Polling at a return point is ok though). Sure is
907 // a lot of bother for a deprecated feature...
908 //
909 // We don't deliver an async exception if the thread state is
910 // _thread_in_native_trans so JNI functions won't be called with
911 // a surprising pending exception. If the thread state is going back to java,
912 // async exception is checked in check_special_condition_for_native_trans().
913
914 if (state != _thread_blocked_trans &&
915 state != _thread_in_vm_trans &&
916 thread->has_special_runtime_exit_condition()) {
917 thread->handle_special_runtime_exit_condition(
918 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
919 }
920 }
921
922 // ------------------------------------------------------------------------------------------------------
923 // Exception handlers
924
925
926 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
927 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
928 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
929 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
930
931 if (ShowSafepointMsgs) {
932 tty->print("handle_polling_page_exception: ");
933 }
934
935 if (PrintSafepointStatistics) {
936 inc_page_trap_count();
937 }
938
939 ThreadSafepointState* state = thread->safepoint_state();
940
941 state->handle_polling_page_exception();
942 }
943
944
945 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
946 if (!timeout_error_printed) {
947 timeout_error_printed = true;
948 // Print out the thread info which didn't reach the safepoint for debugging
949 // purposes (useful when there are lots of threads in the debugger).
950 tty->cr();
951 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
952 if (reason == _spinning_timeout) {
953 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
954 } else if (reason == _blocking_timeout) {
955 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
956 }
957
958 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
959 ThreadSafepointState *cur_state;
960 ResourceMark rm;
961 for(JavaThread *cur_thread = Threads::first(); cur_thread;
962 cur_thread = cur_thread->next()) {
963 cur_state = cur_thread->safepoint_state();
964
965 if (cur_thread->thread_state() != _thread_blocked &&
966 ((reason == _spinning_timeout && cur_state->is_running()) ||
967 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
968 tty->print("# ");
969 cur_thread->print();
970 tty->cr();
971 }
972 }
973 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
974 }
975
976 // To debug the long safepoint, specify both DieOnSafepointTimeout &
977 // ShowMessageBoxOnError.
978 if (DieOnSafepointTimeout) {
979 VM_Operation *op = VMThread::vm_operation();
980 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
981 SafepointTimeoutDelay,
982 op != NULL ? op->name() : "no vm operation");
983 }
984 }
985
986
987 // -------------------------------------------------------------------------------------------------------
988 // Implementation of ThreadSafepointState
989
990 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
991 _thread = thread;
992 _type = _running;
993 _has_called_back = false;
994 _at_poll_safepoint = false;
995 }
996
997 void ThreadSafepointState::create(JavaThread *thread) {
998 ThreadSafepointState *state = new ThreadSafepointState(thread);
999 thread->set_safepoint_state(state);
1000 }
1001
1002 void ThreadSafepointState::destroy(JavaThread *thread) {
1003 if (thread->safepoint_state()) {
1004 delete(thread->safepoint_state());
1005 thread->set_safepoint_state(NULL);
1006 }
1007 }
1008
1009 void ThreadSafepointState::examine_state_of_thread() {
1010 assert(is_running(), "better be running or just have hit safepoint poll");
1011
1012 JavaThreadState state = _thread->thread_state();
1013
1014 // Save the state at the start of safepoint processing.
1015 _orig_thread_state = state;
1016
1017 // Check for a thread that is suspended. Note that thread resume tries
1018 // to grab the Threads_lock which we own here, so a thread cannot be
1019 // resumed during safepoint synchronization.
1020
1021 // We check to see if this thread is suspended without locking to
1022 // avoid deadlocking with a third thread that is waiting for this
1023 // thread to be suspended. The third thread can notice the safepoint
1024 // that we're trying to start at the beginning of its SR_lock->wait()
1025 // call. If that happens, then the third thread will block on the
1026 // safepoint while still holding the underlying SR_lock. We won't be
1027 // able to get the SR_lock and we'll deadlock.
1028 //
1029 // We don't need to grab the SR_lock here for two reasons:
1030 // 1) The suspend flags are both volatile and are set with an
1031 // Atomic::cmpxchg() call so we should see the suspended
1032 // state right away.
1033 // 2) We're being called from the safepoint polling loop; if
1034 // we don't see the suspended state on this iteration, then
1035 // we'll come around again.
1036 //
1037 bool is_suspended = _thread->is_ext_suspended();
1038 if (is_suspended) {
1039 roll_forward(_at_safepoint);
1040 return;
1041 }
1042
1043 // Some JavaThread states have an initial safepoint state of
1044 // running, but are actually at a safepoint. We will happily
1045 // agree and update the safepoint state here.
1046 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
1047 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
1048 roll_forward(_at_safepoint);
1049 return;
1050 }
1051
1052 if (state == _thread_in_vm) {
1053 roll_forward(_call_back);
1054 return;
1055 }
1056
1057 // All other thread states will continue to run until they
1058 // transition and self-block in state _blocked
1059 // Safepoint polling in compiled code causes the Java threads to do the same.
1060 // Note: new threads may require a malloc so they must be allowed to finish
1061
1062 assert(is_running(), "examine_state_of_thread on non-running thread");
1063 return;
1064 }
1065
1066 // Returns true is thread could not be rolled forward at present position.
1067 void ThreadSafepointState::roll_forward(suspend_type type) {
1068 _type = type;
1069
1070 switch(_type) {
1071 case _at_safepoint:
1072 SafepointSynchronize::signal_thread_at_safepoint();
1073 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
1074 if (_thread->in_critical()) {
1075 // Notice that this thread is in a critical section
1076 SafepointSynchronize::increment_jni_active_count();
1077 }
1078 break;
1079
1080 case _call_back:
1081 set_has_called_back(false);
1082 break;
1083
1084 case _running:
1085 default:
1086 ShouldNotReachHere();
1087 }
1088 }
1089
1090 void ThreadSafepointState::restart() {
1091 switch(type()) {
1092 case _at_safepoint:
1093 case _call_back:
1094 break;
1095
1096 case _running:
1097 default:
1098 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
1099 p2i(_thread), _type);
1100 _thread->print();
1101 ShouldNotReachHere();
1102 }
1103 _type = _running;
1104 set_has_called_back(false);
1105 }
1106
1107
1108 void ThreadSafepointState::print_on(outputStream *st) const {
1109 const char *s = NULL;
1110
1111 switch(_type) {
1112 case _running : s = "_running"; break;
1113 case _at_safepoint : s = "_at_safepoint"; break;
1114 case _call_back : s = "_call_back"; break;
1115 default:
1116 ShouldNotReachHere();
1117 }
1118
1119 st->print_cr("Thread: " INTPTR_FORMAT
1120 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1121 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
1122 _at_poll_safepoint);
1123
1124 _thread->print_thread_state_on(st);
1125 }
1126
1127 // ---------------------------------------------------------------------------------------------------------------------
1128
1129 // Block the thread at the safepoint poll or poll return.
1130 void ThreadSafepointState::handle_polling_page_exception() {
1131
1132 // Check state. block() will set thread state to thread_in_vm which will
1133 // cause the safepoint state _type to become _call_back.
1134 assert(type() == ThreadSafepointState::_running,
1135 "polling page exception on thread not running state");
1136
1137 // Step 1: Find the nmethod from the return address
1138 if (ShowSafepointMsgs && Verbose) {
1139 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
1140 }
1141 address real_return_addr = thread()->saved_exception_pc();
1142
1143 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1144 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1145 CompiledMethod* nm = (CompiledMethod*)cb;
1146
1147 // Find frame of caller
1148 frame stub_fr = thread()->last_frame();
1149 CodeBlob* stub_cb = stub_fr.cb();
1150 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1151 RegisterMap map(thread(), true);
1152 frame caller_fr = stub_fr.sender(&map);
1153
1154 // Should only be poll_return or poll
1155 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1156
1157 // This is a poll immediately before a return. The exception handling code
1158 // has already had the effect of causing the return to occur, so the execution
1159 // will continue immediately after the call. In addition, the oopmap at the
1160 // return point does not mark the return value as an oop (if it is), so
1161 // it needs a handle here to be updated.
1162 if( nm->is_at_poll_return(real_return_addr) ) {
1163 // See if return type is an oop.
1164 bool return_oop = nm->method()->is_returning_oop();
1165 Handle return_value;
1166 if (return_oop) {
1167 // The oop result has been saved on the stack together with all
1168 // the other registers. In order to preserve it over GCs we need
1169 // to keep it in a handle.
1170 oop result = caller_fr.saved_oop_result(&map);
1171 assert(result == NULL || result->is_oop(), "must be oop");
1172 return_value = Handle(thread(), result);
1173 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1174 }
1175
1176 // Block the thread
1177 SafepointSynchronize::block(thread());
1178
1179 // restore oop result, if any
1180 if (return_oop) {
1181 caller_fr.set_saved_oop_result(&map, return_value());
1182 }
1183 }
1184
1185 // This is a safepoint poll. Verify the return address and block.
1186 else {
1187 set_at_poll_safepoint(true);
1188
1189 // verify the blob built the "return address" correctly
1190 assert(real_return_addr == caller_fr.pc(), "must match");
1191
1192 // Block the thread
1193 SafepointSynchronize::block(thread());
1194 set_at_poll_safepoint(false);
1195
1196 // If we have a pending async exception deoptimize the frame
1197 // as otherwise we may never deliver it.
1198 if (thread()->has_async_condition()) {
1199 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1200 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1201 }
1202
1203 // If an exception has been installed we must check for a pending deoptimization
1204 // Deoptimize frame if exception has been thrown.
1205
1206 if (thread()->has_pending_exception() ) {
1207 RegisterMap map(thread(), true);
1208 frame caller_fr = stub_fr.sender(&map);
1209 if (caller_fr.is_deoptimized_frame()) {
1210 // The exception patch will destroy registers that are still
1211 // live and will be needed during deoptimization. Defer the
1212 // Async exception should have deferred the exception until the
1213 // next safepoint which will be detected when we get into
1214 // the interpreter so if we have an exception now things
1215 // are messed up.
1216
1217 fatal("Exception installed and deoptimization is pending");
1218 }
1219 }
1220 }
1221 }
1222
1223
1224 //
1225 // Statistics & Instrumentations
1226 //
1227 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1228 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1229 int SafepointSynchronize::_cur_stat_index = 0;
1230 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1231 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1232 jlong SafepointSynchronize::_max_sync_time = 0;
1233 jlong SafepointSynchronize::_max_vmop_time = 0;
1234 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1235
1236 static jlong cleanup_end_time = 0;
1237 static bool need_to_track_page_armed_status = false;
1238 static bool init_done = false;
1239
1240 // Helper method to print the header.
1241 static void print_header() {
1242 tty->print(" vmop "
1243 "[threads: total initially_running wait_to_block] ");
1244 tty->print("[time: spin block sync cleanup vmop] ");
1245
1246 // no page armed status printed out if it is always armed.
1247 if (need_to_track_page_armed_status) {
1248 tty->print("page_armed ");
1249 }
1250
1251 tty->print_cr("page_trap_count");
1252 }
1253
1254 void SafepointSynchronize::deferred_initialize_stat() {
1255 if (init_done) return;
1256
1257 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1258 // be printed right away, in which case, _safepoint_stats will regress to
1259 // a single element array. Otherwise, it is a circular ring buffer with default
1260 // size of PrintSafepointStatisticsCount.
1261 int stats_array_size;
1262 if (PrintSafepointStatisticsTimeout > 0) {
1263 stats_array_size = 1;
1264 PrintSafepointStatistics = true;
1265 } else {
1266 stats_array_size = PrintSafepointStatisticsCount;
1267 }
1268 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1269 * sizeof(SafepointStats), mtInternal);
1270 guarantee(_safepoint_stats != NULL,
1271 "not enough memory for safepoint instrumentation data");
1272
1273 if (DeferPollingPageLoopCount >= 0) {
1274 need_to_track_page_armed_status = true;
1275 }
1276 init_done = true;
1277 }
1278
1279 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1280 assert(init_done, "safepoint statistics array hasn't been initialized");
1281 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1282
1283 spstat->_time_stamp = _ts_of_current_safepoint;
1284
1285 VM_Operation *op = VMThread::vm_operation();
1286 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1287 if (op != NULL) {
1288 _safepoint_reasons[spstat->_vmop_type]++;
1289 }
1290
1291 spstat->_nof_total_threads = nof_threads;
1292 spstat->_nof_initial_running_threads = nof_running;
1293 spstat->_nof_threads_hit_page_trap = 0;
1294
1295 // Records the start time of spinning. The real time spent on spinning
1296 // will be adjusted when spin is done. Same trick is applied for time
1297 // spent on waiting for threads to block.
1298 if (nof_running != 0) {
1299 spstat->_time_to_spin = os::javaTimeNanos();
1300 } else {
1301 spstat->_time_to_spin = 0;
1302 }
1303 }
1304
1305 void SafepointSynchronize::update_statistics_on_spin_end() {
1306 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1307
1308 jlong cur_time = os::javaTimeNanos();
1309
1310 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1311 if (spstat->_nof_initial_running_threads != 0) {
1312 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1313 }
1314
1315 if (need_to_track_page_armed_status) {
1316 spstat->_page_armed = (PageArmed == 1);
1317 }
1318
1319 // Records the start time of waiting for to block. Updated when block is done.
1320 if (_waiting_to_block != 0) {
1321 spstat->_time_to_wait_to_block = cur_time;
1322 } else {
1323 spstat->_time_to_wait_to_block = 0;
1324 }
1325 }
1326
1327 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1328 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1329
1330 if (spstat->_nof_threads_wait_to_block != 0) {
1331 spstat->_time_to_wait_to_block = end_time -
1332 spstat->_time_to_wait_to_block;
1333 }
1334
1335 // Records the end time of sync which will be used to calculate the total
1336 // vm operation time. Again, the real time spending in syncing will be deducted
1337 // from the start of the sync time later when end_statistics is called.
1338 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1339 if (spstat->_time_to_sync > _max_sync_time) {
1340 _max_sync_time = spstat->_time_to_sync;
1341 }
1342
1343 spstat->_time_to_do_cleanups = end_time;
1344 }
1345
1346 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1347 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1348
1349 // Record how long spent in cleanup tasks.
1350 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1351
1352 cleanup_end_time = end_time;
1353 }
1354
1355 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1356 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1357
1358 // Update the vm operation time.
1359 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1360 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1361 _max_vmop_time = spstat->_time_to_exec_vmop;
1362 }
1363 // Only the sync time longer than the specified
1364 // PrintSafepointStatisticsTimeout will be printed out right away.
1365 // By default, it is -1 meaning all samples will be put into the list.
1366 if ( PrintSafepointStatisticsTimeout > 0) {
1367 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1368 print_statistics();
1369 }
1370 } else {
1371 // The safepoint statistics will be printed out when the _safepoin_stats
1372 // array fills up.
1373 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1374 print_statistics();
1375 _cur_stat_index = 0;
1376 } else {
1377 _cur_stat_index++;
1378 }
1379 }
1380 }
1381
1382 void SafepointSynchronize::print_statistics() {
1383 SafepointStats* sstats = _safepoint_stats;
1384
1385 for (int index = 0; index <= _cur_stat_index; index++) {
1386 if (index % 30 == 0) {
1387 print_header();
1388 }
1389 sstats = &_safepoint_stats[index];
1390 tty->print("%.3f: ", sstats->_time_stamp);
1391 tty->print("%-26s ["
1392 INT32_FORMAT_W(8) INT32_FORMAT_W(11) INT32_FORMAT_W(15)
1393 " ] ",
1394 sstats->_vmop_type == -1 ? "no vm operation" :
1395 VM_Operation::name(sstats->_vmop_type),
1396 sstats->_nof_total_threads,
1397 sstats->_nof_initial_running_threads,
1398 sstats->_nof_threads_wait_to_block);
1399 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1400 tty->print(" ["
1401 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1402 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1403 INT64_FORMAT_W(6) " ] ",
1404 sstats->_time_to_spin / MICROUNITS,
1405 sstats->_time_to_wait_to_block / MICROUNITS,
1406 sstats->_time_to_sync / MICROUNITS,
1407 sstats->_time_to_do_cleanups / MICROUNITS,
1408 sstats->_time_to_exec_vmop / MICROUNITS);
1409
1410 if (need_to_track_page_armed_status) {
1411 tty->print(INT32_FORMAT " ", sstats->_page_armed);
1412 }
1413 tty->print_cr(INT32_FORMAT " ", sstats->_nof_threads_hit_page_trap);
1414 }
1415 }
1416
1417 // This method will be called when VM exits. It will first call
1418 // print_statistics to print out the rest of the sampling. Then
1419 // it tries to summarize the sampling.
1420 void SafepointSynchronize::print_stat_on_exit() {
1421 if (_safepoint_stats == NULL) return;
1422
1423 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1424
1425 // During VM exit, end_statistics may not get called and in that
1426 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1427 // don't print it out.
1428 // Approximate the vm op time.
1429 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1430 os::javaTimeNanos() - cleanup_end_time;
1431
1432 if ( PrintSafepointStatisticsTimeout < 0 ||
1433 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1434 print_statistics();
1435 }
1436 tty->cr();
1437
1438 // Print out polling page sampling status.
1439 if (!need_to_track_page_armed_status) {
1440 tty->print_cr("Polling page always armed");
1441 } else {
1442 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
1443 DeferPollingPageLoopCount);
1444 }
1445
1446 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1447 if (_safepoint_reasons[index] != 0) {
1448 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1449 _safepoint_reasons[index]);
1450 }
1451 }
1452
1453 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1454 _coalesced_vmop_count);
1455 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1456 _max_sync_time / MICROUNITS);
1457 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1458 INT64_FORMAT_W(5) " ms",
1459 _max_vmop_time / MICROUNITS);
1460 }
1461
1462 // ------------------------------------------------------------------------------------------------
1463 // Non-product code
1464
1465 #ifndef PRODUCT
1466
1467 void SafepointSynchronize::print_state() {
1468 if (_state == _not_synchronized) {
1469 tty->print_cr("not synchronized");
1470 } else if (_state == _synchronizing || _state == _synchronized) {
1471 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1472 "synchronized");
1473
1474 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1475 cur->safepoint_state()->print();
1476 }
1477 }
1478 }
1479
1480 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1481 if (ShowSafepointMsgs) {
1482 va_list ap;
1483 va_start(ap, format);
1484 tty->vprint_cr(format, ap);
1485 va_end(ap);
1486 }
1487 }
1488
1489 #endif // !PRODUCT