1 /*
2 * Copyright (c) 1997, 2018, 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/classLoaderDataGraph.inline.hpp"
27 #include "classfile/stringTable.hpp"
28 #include "classfile/symbolTable.hpp"
29 #include "classfile/systemDictionary.hpp"
30 #include "code/codeCache.hpp"
31 #include "code/icBuffer.hpp"
32 #include "code/nmethod.hpp"
33 #include "code/pcDesc.hpp"
34 #include "code/scopeDesc.hpp"
35 #include "gc/shared/collectedHeap.hpp"
36 #include "gc/shared/gcLocker.hpp"
37 #include "gc/shared/strongRootsScope.hpp"
38 #include "gc/shared/workgroup.hpp"
39 #include "interpreter/interpreter.hpp"
40 #include "jfr/jfrEvents.hpp"
41 #include "logging/log.hpp"
42 #include "logging/logStream.hpp"
43 #include "memory/resourceArea.hpp"
44 #include "memory/universe.hpp"
45 #include "oops/oop.inline.hpp"
46 #include "oops/symbol.hpp"
47 #include "oops/valueKlass.hpp"
48 #include "runtime/atomic.hpp"
49 #include "runtime/compilationPolicy.hpp"
50 #include "runtime/deoptimization.hpp"
51 #include "runtime/frame.inline.hpp"
52 #include "runtime/interfaceSupport.inline.hpp"
53 #include "runtime/mutexLocker.hpp"
54 #include "runtime/orderAccess.hpp"
55 #include "runtime/osThread.hpp"
56 #include "runtime/safepoint.hpp"
57 #include "runtime/safepointMechanism.inline.hpp"
58 #include "runtime/signature.hpp"
59 #include "runtime/stubCodeGenerator.hpp"
60 #include "runtime/stubRoutines.hpp"
61 #include "runtime/sweeper.hpp"
62 #include "runtime/synchronizer.hpp"
63 #include "runtime/thread.inline.hpp"
64 #include "runtime/threadSMR.hpp"
65 #include "runtime/timerTrace.hpp"
66 #include "services/runtimeService.hpp"
67 #include "utilities/events.hpp"
68 #include "utilities/macros.hpp"
69 #ifdef COMPILER1
70 #include "c1/c1_globals.hpp"
71 #endif
72
73 template <typename E>
74 static void set_current_safepoint_id(E* event, int adjustment = 0) {
75 assert(event != NULL, "invariant");
76 event->set_safepointId(SafepointSynchronize::safepoint_counter() + adjustment);
77 }
78
79 static void post_safepoint_begin_event(EventSafepointBegin* event,
80 int thread_count,
81 int critical_thread_count) {
82 assert(event != NULL, "invariant");
83 assert(event->should_commit(), "invariant");
84 set_current_safepoint_id(event);
85 event->set_totalThreadCount(thread_count);
86 event->set_jniCriticalThreadCount(critical_thread_count);
87 event->commit();
88 }
89
90 static void post_safepoint_cleanup_event(EventSafepointCleanup* event) {
91 assert(event != NULL, "invariant");
92 assert(event->should_commit(), "invariant");
93 set_current_safepoint_id(event);
94 event->commit();
95 }
96
97 static void post_safepoint_synchronize_event(EventSafepointStateSynchronization* event,
98 int initial_number_of_threads,
99 int threads_waiting_to_block,
100 unsigned int iterations) {
101 assert(event != NULL, "invariant");
102 if (event->should_commit()) {
103 // Group this event together with the ones committed after the counter is increased
104 set_current_safepoint_id(event, 1);
105 event->set_initialThreadCount(initial_number_of_threads);
106 event->set_runningThreadCount(threads_waiting_to_block);
107 event->set_iterations(iterations);
108 event->commit();
109 }
110 }
111
112 static void post_safepoint_wait_blocked_event(EventSafepointWaitBlocked* event,
113 int initial_threads_waiting_to_block) {
114 assert(event != NULL, "invariant");
115 assert(event->should_commit(), "invariant");
116 set_current_safepoint_id(event);
117 event->set_runningThreadCount(initial_threads_waiting_to_block);
118 event->commit();
119 }
120
121 static void post_safepoint_cleanup_task_event(EventSafepointCleanupTask* event,
122 const char* name) {
123 assert(event != NULL, "invariant");
124 if (event->should_commit()) {
125 set_current_safepoint_id(event);
126 event->set_name(name);
127 event->commit();
128 }
129 }
130
131 static void post_safepoint_end_event(EventSafepointEnd* event) {
132 assert(event != NULL, "invariant");
133 if (event->should_commit()) {
134 // Group this event together with the ones committed before the counter increased
135 set_current_safepoint_id(event, -1);
136 event->commit();
137 }
138 }
139
140 // --------------------------------------------------------------------------------------------------
141 // Implementation of Safepoint begin/end
142
143 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
144 volatile int SafepointSynchronize::_waiting_to_block = 0;
145 volatile uint64_t SafepointSynchronize::_safepoint_counter = 0;
146 int SafepointSynchronize::_current_jni_active_count = 0;
147 long SafepointSynchronize::_end_of_last_safepoint = 0;
148 int SafepointSynchronize::_defer_thr_suspend_loop_count = 4000;
149 static const int safepoint_spin_before_yield = 2000;
150 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
151 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
152 static bool timeout_error_printed = false;
153
154
155 // Statistic related statics
156 julong SafepointSynchronize::_coalesced_vmop_count = 0;
157 static jlong _safepoint_begin_time = 0;
158 static float _ts_of_current_safepoint = 0.0f;
159 static volatile int _nof_threads_hit_polling_page = 0;
160
161 // Roll all threads forward to a safepoint and suspend them all
162 void SafepointSynchronize::begin() {
163 EventSafepointBegin begin_event;
164 Thread* myThread = Thread::current();
165 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
166
167 if (log_is_enabled(Debug, safepoint, stats)) {
168 _safepoint_begin_time = os::javaTimeNanos();
169 _ts_of_current_safepoint = tty->time_stamp().seconds();
170 _nof_threads_hit_polling_page = 0;
171 }
172
173 Universe::heap()->safepoint_synchronize_begin();
174
175 // By getting the Threads_lock, we assure that no threads are about to start or
176 // exit. It is released again in SafepointSynchronize::end().
177 Threads_lock->lock();
178
179 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
180
181 int nof_threads = Threads::number_of_threads();
182
183 log_debug(safepoint)("Safepoint synchronization initiated. (%d threads)", nof_threads);
184
185 RuntimeService::record_safepoint_begin();
186
187 MutexLocker mu(Safepoint_lock);
188
189 // Reset the count of active JNI critical threads
190 _current_jni_active_count = 0;
191
192 // Set number of threads to wait for, before we initiate the callbacks
193 _waiting_to_block = nof_threads;
194 TryingToBlock = 0 ;
195 int still_running = nof_threads;
196
197 // Save the starting time, so that it can be compared to see if this has taken
198 // too long to complete.
199 jlong safepoint_limit_time = 0;
200 timeout_error_printed = false;
201
202 // Begin the process of bringing the system to a safepoint.
203 // Java threads can be in several different states and are
204 // stopped by different mechanisms:
205 //
206 // 1. Running interpreted
207 // The interpreter dispatch table is changed to force it to
208 // check for a safepoint condition between bytecodes.
209 // 2. Running in native code
210 // When returning from the native code, a Java thread must check
211 // the safepoint _state to see if we must block. If the
212 // VM thread sees a Java thread in native, it does
213 // not wait for this thread to block. The order of the memory
214 // writes and reads of both the safepoint state and the Java
215 // threads state is critical. In order to guarantee that the
216 // memory writes are serialized with respect to each other,
217 // the VM thread issues a memory barrier instruction.
218 // 3. Running compiled Code
219 // Compiled code reads a global (Safepoint Polling) page that
220 // is set to fault if we are trying to get to a safepoint.
221 // 4. Blocked
222 // A thread which is blocked will not be allowed to return from the
223 // block condition until the safepoint operation is complete.
224 // 5. In VM or Transitioning between states
225 // If a Java thread is currently running in the VM or transitioning
226 // between states, the safepointing code will wait for the thread to
227 // block itself when it attempts transitions to a new state.
228 //
229 {
230 EventSafepointStateSynchronization sync_event;
231 int initial_running = 0;
232
233 _state = _synchronizing;
234
235 if (SafepointMechanism::uses_thread_local_poll()) {
236 // Arming the per thread poll while having _state != _not_synchronized means safepointing
237 log_trace(safepoint)("Setting thread local yield flag for threads");
238 OrderAccess::storestore(); // storestore, global state -> local state
239 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
240 // Make sure the threads start polling, it is time to yield.
241 SafepointMechanism::arm_local_poll(cur);
242 }
243 }
244 OrderAccess::fence(); // storestore|storeload, global state -> local state
245
246 if (SafepointMechanism::uses_global_page_poll()) {
247 // Make interpreter safepoint aware
248 Interpreter::notice_safepoints();
249
250 // Make polling safepoint aware
251 guarantee (PageArmed == 0, "invariant") ;
252 PageArmed = 1 ;
253 os::make_polling_page_unreadable();
254 }
255
256 // Consider using active_processor_count() ... but that call is expensive.
257 int ncpus = os::processor_count() ;
258 unsigned int iterations = 0;
259
260 {
261 JavaThreadIteratorWithHandle jtiwh;
262 #ifdef ASSERT
263 for (; JavaThread *cur = jtiwh.next(); ) {
264 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
265 // Clear the visited flag to ensure that the critical counts are collected properly.
266 cur->set_visited_for_critical_count(false);
267 }
268 #endif // ASSERT
269
270 if (SafepointTimeout)
271 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
272
273 // Iterate through all threads until it have been determined how to stop them all at a safepoint
274 int steps = 0 ;
275 while(still_running > 0) {
276 jtiwh.rewind();
277 for (; JavaThread *cur = jtiwh.next(); ) {
278 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
279 ThreadSafepointState *cur_state = cur->safepoint_state();
280 if (cur_state->is_running()) {
281 cur_state->examine_state_of_thread();
282 if (!cur_state->is_running()) {
283 still_running--;
284 // consider adjusting steps downward:
285 // steps = 0
286 // steps -= NNN
287 // steps >>= 1
288 // steps = MIN(steps, 2000-100)
289 // if (iterations != 0) steps -= NNN
290 }
291 LogTarget(Trace, safepoint) lt;
292 if (lt.is_enabled()) {
293 ResourceMark rm;
294 LogStream ls(lt);
295 cur_state->print_on(&ls);
296 }
297 }
298 }
299
300 if (iterations == 0) {
301 initial_running = still_running;
302 if (log_is_enabled(Debug, safepoint, stats)) {
303 begin_statistics(nof_threads, still_running);
304 }
305 }
306
307 if (still_running > 0) {
308 // Check for if it takes to long
309 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
310 print_safepoint_timeout(_spinning_timeout);
311 }
312
313 // Spin to avoid context switching.
314 // There's a tension between allowing the mutators to run (and rendezvous)
315 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
316 // a mutator might otherwise use profitably to reach a safepoint. Excessive
317 // spinning by the VM thread on a saturated system can increase rendezvous latency.
318 // Blocking or yielding incur their own penalties in the form of context switching
319 // and the resultant loss of $ residency.
320 //
321 // Further complicating matters is that yield() does not work as naively expected
322 // on many platforms -- yield() does not guarantee that any other ready threads
323 // will run. As such we revert to naked_short_sleep() after some number of iterations.
324 // nakes_short_sleep() is implemented as a short unconditional sleep.
325 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
326 // can actually increase the time it takes the VM thread to detect that a system-wide
327 // stop-the-world safepoint has been reached. In a pathological scenario such as that
328 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
329 // In that case the mutators will be stalled waiting for the safepoint to complete and the
330 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
331 // will eventually wake up and detect that all mutators are safe, at which point
332 // we'll again make progress.
333 //
334 // Beware too that that the VMThread typically runs at elevated priority.
335 // Its default priority is higher than the default mutator priority.
336 // Obviously, this complicates spinning.
337 //
338 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
339 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
340 //
341 // See the comments in synchronizer.cpp for additional remarks on spinning.
342 //
343 // In the future we might:
344 // -- Modify the safepoint scheme to avoid potentially unbounded spinning.
345 // This is tricky as the path used by a thread exiting the JVM (say on
346 // on JNI call-out) simply stores into its state field. The burden
347 // is placed on the VM thread, which must poll (spin).
348 // -- Find something useful to do while spinning. If the safepoint is GC-related
349 // we might aggressively scan the stacks of threads that are already safe.
350 // -- YieldTo() any still-running mutators that are ready but OFFPROC.
351 // -- Check system saturation. If the system is not fully saturated then
352 // simply spin and avoid sleep/yield.
353 // -- As still-running mutators rendezvous they could unpark the sleeping
354 // VMthread. This works well for still-running mutators that become
355 // safe. The VMthread must still poll for mutators that call-out.
356 // -- Drive the policy on time-since-begin instead of iterations.
357 // -- Consider making the spin duration a function of the # of CPUs:
358 // Spin = (((ncpus-1) * M) + K) + F(still_running)
359 // Alternately, instead of counting iterations of the outer loop
360 // we could count the # of threads visited in the inner loop, above.
361 // -- On windows consider using the return value from SwitchThreadTo()
362 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
363
364 if (int(iterations) == -1) { // overflow - something is wrong.
365 // We can only overflow here when we are using global
366 // polling pages. We keep this guarantee in its original
367 // form so that searches of the bug database for this
368 // failure mode find the right bugs.
369 guarantee (PageArmed == 0, "invariant");
370 }
371
372 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
373 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
374 ++steps ;
375 if (ncpus > 1 && steps < safepoint_spin_before_yield) {
376 SpinPause() ; // MP-Polite spin
377 } else
378 if (steps < _defer_thr_suspend_loop_count) {
379 os::naked_yield() ;
380 } else {
381 os::naked_short_sleep(1);
382 }
383
384 iterations ++ ;
385 }
386 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
387 }
388 } // ThreadsListHandle destroyed here.
389 assert(still_running == 0, "sanity check");
390
391 if (log_is_enabled(Debug, safepoint, stats)) {
392 update_statistics_on_spin_end();
393 }
394 if (sync_event.should_commit()) {
395 post_safepoint_synchronize_event(&sync_event, initial_running, _waiting_to_block, iterations);
396 }
397 }
398
399 // wait until all threads are stopped
400 {
401 EventSafepointWaitBlocked wait_blocked_event;
402 int initial_waiting_to_block = _waiting_to_block;
403
404 while (_waiting_to_block > 0) {
405 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
406 if (!SafepointTimeout || timeout_error_printed) {
407 Safepoint_lock->wait(true); // true, means with no safepoint checks
408 } else {
409 // Compute remaining time
410 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
411
412 // If there is no remaining time, then there is an error
413 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
414 print_safepoint_timeout(_blocking_timeout);
415 }
416 }
417 }
418 assert(_waiting_to_block == 0, "sanity check");
419
420 #ifndef PRODUCT
421 if (SafepointTimeout) {
422 jlong current_time = os::javaTimeNanos();
423 if (safepoint_limit_time < current_time) {
424 log_warning(safepoint)("# SafepointSynchronize: Finished after "
425 INT64_FORMAT_W(6) " ms",
426 (int64_t)((current_time - safepoint_limit_time) / MICROUNITS +
427 (jlong)SafepointTimeoutDelay));
428 }
429 }
430 #endif
431
432 assert((_safepoint_counter & 0x1) == 0, "must be even");
433 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
434 _safepoint_counter ++;
435
436 // Record state
437 _state = _synchronized;
438
439 OrderAccess::fence();
440 if (wait_blocked_event.should_commit()) {
441 post_safepoint_wait_blocked_event(&wait_blocked_event, initial_waiting_to_block);
442 }
443 }
444
445 #ifdef ASSERT
446 // Make sure all the threads were visited.
447 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
448 assert(cur->was_visited_for_critical_count(), "missed a thread");
449 }
450 #endif // ASSERT
451
452 // Update the count of active JNI critical regions
453 GCLocker::set_jni_lock_count(_current_jni_active_count);
454
455 log_info(safepoint)("Entering safepoint region: %s", VMThread::vm_safepoint_description());
456
457 RuntimeService::record_safepoint_synchronized();
458 if (log_is_enabled(Debug, safepoint, stats)) {
459 update_statistics_on_sync_end(os::javaTimeNanos());
460 }
461
462 // Call stuff that needs to be run when a safepoint is just about to be completed
463 {
464 EventSafepointCleanup cleanup_event;
465 do_cleanup_tasks();
466 if (cleanup_event.should_commit()) {
467 post_safepoint_cleanup_event(&cleanup_event);
468 }
469 }
470
471 if (log_is_enabled(Debug, safepoint, stats)) {
472 // Record how much time spend on the above cleanup tasks
473 update_statistics_on_cleanup_end(os::javaTimeNanos());
474 }
475
476 if (begin_event.should_commit()) {
477 post_safepoint_begin_event(&begin_event, nof_threads, _current_jni_active_count);
478 }
479 }
480
481 // Wake up all threads, so they are ready to resume execution after the safepoint
482 // operation has been carried out
483 void SafepointSynchronize::end() {
484 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
485 assert((_safepoint_counter & 0x1) == 1, "must be odd");
486 EventSafepointEnd event;
487 _safepoint_counter ++;
488 // memory fence isn't required here since an odd _safepoint_counter
489 // value can do no harm and a fence is issued below anyway.
490
491 DEBUG_ONLY(Thread* myThread = Thread::current();)
492 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
493
494 if (log_is_enabled(Debug, safepoint, stats)) {
495 end_statistics(os::javaTimeNanos());
496 }
497
498 {
499 JavaThreadIteratorWithHandle jtiwh;
500 #ifdef ASSERT
501 // A pending_exception cannot be installed during a safepoint. The threads
502 // may install an async exception after they come back from a safepoint into
503 // pending_exception after they unblock. But that should happen later.
504 for (; JavaThread *cur = jtiwh.next(); ) {
505 assert (!(cur->has_pending_exception() &&
506 cur->safepoint_state()->is_at_poll_safepoint()),
507 "safepoint installed a pending exception");
508 }
509 #endif // ASSERT
510
511 if (PageArmed) {
512 assert(SafepointMechanism::uses_global_page_poll(), "sanity");
513 // Make polling safepoint aware
514 os::make_polling_page_readable();
515 PageArmed = 0 ;
516 }
517
518 if (SafepointMechanism::uses_global_page_poll()) {
519 // Remove safepoint check from interpreter
520 Interpreter::ignore_safepoints();
521 }
522
523 {
524 MutexLocker mu(Safepoint_lock);
525
526 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
527
528 if (SafepointMechanism::uses_thread_local_poll()) {
529 _state = _not_synchronized;
530 OrderAccess::storestore(); // global state -> local state
531 jtiwh.rewind();
532 for (; JavaThread *current = jtiwh.next(); ) {
533 ThreadSafepointState* cur_state = current->safepoint_state();
534 cur_state->restart(); // TSS _running
535 SafepointMechanism::disarm_local_poll(current);
536 }
537 log_info(safepoint)("Leaving safepoint region");
538 } else {
539 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
540 // when they get restarted.
541 _state = _not_synchronized;
542 OrderAccess::fence();
543
544 log_info(safepoint)("Leaving safepoint region");
545
546 // Start suspended threads
547 jtiwh.rewind();
548 for (; JavaThread *current = jtiwh.next(); ) {
549 ThreadSafepointState* cur_state = current->safepoint_state();
550 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
551 cur_state->restart();
552 assert(cur_state->is_running(), "safepoint state has not been reset");
553 }
554 }
555
556 RuntimeService::record_safepoint_end();
557
558 // Release threads lock, so threads can be created/destroyed again.
559 // It will also release all threads blocked in signal_thread_blocked.
560 Threads_lock->unlock();
561 }
562 } // ThreadsListHandle destroyed here.
563
564 Universe::heap()->safepoint_synchronize_end();
565 // record this time so VMThread can keep track how much time has elapsed
566 // since last safepoint.
567 _end_of_last_safepoint = os::javaTimeMillis();
568 if (event.should_commit()) {
569 post_safepoint_end_event(&event);
570 }
571 }
572
573 bool SafepointSynchronize::is_cleanup_needed() {
574 // Need a safepoint if there are many monitors to deflate.
575 if (ObjectSynchronizer::is_cleanup_needed()) return true;
576 // Need a safepoint if some inline cache buffers is non-empty
577 if (!InlineCacheBuffer::is_empty()) return true;
578 return false;
579 }
580
581 class ParallelSPCleanupThreadClosure : public ThreadClosure {
582 private:
583 CodeBlobClosure* _nmethod_cl;
584 DeflateMonitorCounters* _counters;
585
586 public:
587 ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) :
588 _nmethod_cl(UseCodeAging ? NMethodSweeper::prepare_reset_hotness_counters() : NULL),
589 _counters(counters) {}
590
591 void do_thread(Thread* thread) {
592 ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters);
593 if (_nmethod_cl != NULL && thread->is_Java_thread() &&
594 ! thread->is_Code_cache_sweeper_thread()) {
595 JavaThread* jt = (JavaThread*) thread;
596 jt->nmethods_do(_nmethod_cl);
597 }
598 }
599 };
600
601 class ParallelSPCleanupTask : public AbstractGangTask {
602 private:
603 SubTasksDone _subtasks;
604 ParallelSPCleanupThreadClosure _cleanup_threads_cl;
605 uint _num_workers;
606 DeflateMonitorCounters* _counters;
607 public:
608 ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
609 AbstractGangTask("Parallel Safepoint Cleanup"),
610 _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)),
611 _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
612 _num_workers(num_workers),
613 _counters(counters) {}
614
615 void work(uint worker_id) {
616 // All threads deflate monitors and mark nmethods (if necessary).
617 Threads::possibly_parallel_threads_do(true, &_cleanup_threads_cl);
618
619 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
620 const char* name = "deflating global idle monitors";
621 EventSafepointCleanupTask event;
622 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
623 ObjectSynchronizer::deflate_idle_monitors(_counters);
624 if (event.should_commit()) {
625 post_safepoint_cleanup_task_event(&event, name);
626 }
627 }
628
629 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
630 const char* name = "updating inline caches";
631 EventSafepointCleanupTask event;
632 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
633 InlineCacheBuffer::update_inline_caches();
634 if (event.should_commit()) {
635 post_safepoint_cleanup_task_event(&event, name);
636 }
637 }
638
639 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
640 const char* name = "compilation policy safepoint handler";
641 EventSafepointCleanupTask event;
642 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
643 CompilationPolicy::policy()->do_safepoint_work();
644 if (event.should_commit()) {
645 post_safepoint_cleanup_task_event(&event, name);
646 }
647 }
648
649 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
650 if (SymbolTable::needs_rehashing()) {
651 const char* name = "rehashing symbol table";
652 EventSafepointCleanupTask event;
653 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
654 SymbolTable::rehash_table();
655 if (event.should_commit()) {
656 post_safepoint_cleanup_task_event(&event, name);
657 }
658 }
659 }
660
661 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
662 if (StringTable::needs_rehashing()) {
663 const char* name = "rehashing string table";
664 EventSafepointCleanupTask event;
665 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
666 StringTable::rehash_table();
667 if (event.should_commit()) {
668 post_safepoint_cleanup_task_event(&event, name);
669 }
670 }
671 }
672
673 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) {
674 // CMS delays purging the CLDG until the beginning of the next safepoint and to
675 // make sure concurrent sweep is done
676 const char* name = "purging class loader data graph";
677 EventSafepointCleanupTask event;
678 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
679 ClassLoaderDataGraph::purge_if_needed();
680 if (event.should_commit()) {
681 post_safepoint_cleanup_task_event(&event, name);
682 }
683 }
684
685 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_SYSTEM_DICTIONARY_RESIZE)) {
686 const char* name = "resizing system dictionaries";
687 EventSafepointCleanupTask event;
688 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
689 ClassLoaderDataGraph::resize_if_needed();
690 if (event.should_commit()) {
691 post_safepoint_cleanup_task_event(&event, name);
692 }
693 }
694
695 _subtasks.all_tasks_completed(_num_workers);
696 }
697 };
698
699 // Various cleaning tasks that should be done periodically at safepoints.
700 void SafepointSynchronize::do_cleanup_tasks() {
701
702 TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup));
703
704 // Prepare for monitor deflation.
705 DeflateMonitorCounters deflate_counters;
706 ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
707
708 CollectedHeap* heap = Universe::heap();
709 assert(heap != NULL, "heap not initialized yet?");
710 WorkGang* cleanup_workers = heap->get_safepoint_workers();
711 if (cleanup_workers != NULL) {
712 // Parallel cleanup using GC provided thread pool.
713 uint num_cleanup_workers = cleanup_workers->active_workers();
714 ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
715 StrongRootsScope srs(num_cleanup_workers);
716 cleanup_workers->run_task(&cleanup);
717 } else {
718 // Serial cleanup using VMThread.
719 ParallelSPCleanupTask cleanup(1, &deflate_counters);
720 StrongRootsScope srs(1);
721 cleanup.work(0);
722 }
723
724 // Needs to be done single threaded by the VMThread. This walks
725 // the thread stacks looking for references to metadata before
726 // deciding to remove it from the metaspaces.
727 if (ClassLoaderDataGraph::should_clean_metaspaces_and_reset()) {
728 const char* name = "cleanup live ClassLoaderData metaspaces";
729 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
730 ClassLoaderDataGraph::walk_metadata_and_clean_metaspaces();
731 }
732
733 // Finish monitor deflation.
734 ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
735
736 }
737
738
739 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
740 switch(state) {
741 case _thread_in_native:
742 // native threads are safe if they have no java stack or have walkable stack
743 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
744
745 // blocked threads should have already have walkable stack
746 case _thread_blocked:
747 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
748 return true;
749
750 default:
751 return false;
752 }
753 }
754
755
756 // See if the thread is running inside a lazy critical native and
757 // update the thread critical count if so. Also set a suspend flag to
758 // cause the native wrapper to return into the JVM to do the unlock
759 // once the native finishes.
760 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
761 if (state == _thread_in_native &&
762 thread->has_last_Java_frame() &&
763 thread->frame_anchor()->walkable()) {
764 // This thread might be in a critical native nmethod so look at
765 // the top of the stack and increment the critical count if it
766 // is.
767 frame wrapper_frame = thread->last_frame();
768 CodeBlob* stub_cb = wrapper_frame.cb();
769 if (stub_cb != NULL &&
770 stub_cb->is_nmethod() &&
771 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
772 // A thread could potentially be in a critical native across
773 // more than one safepoint, so only update the critical state on
774 // the first one. When it returns it will perform the unlock.
775 if (!thread->do_critical_native_unlock()) {
776 #ifdef ASSERT
777 if (!thread->in_critical()) {
778 GCLocker::increment_debug_jni_lock_count();
779 }
780 #endif
781 thread->enter_critical();
782 // Make sure the native wrapper calls back on return to
783 // perform the needed critical unlock.
784 thread->set_critical_native_unlock();
785 }
786 }
787 }
788 }
789
790
791
792 // -------------------------------------------------------------------------------------------------------
793 // Implementation of Safepoint callback point
794
795 void SafepointSynchronize::block(JavaThread *thread) {
796 assert(thread != NULL, "thread must be set");
797 assert(thread->is_Java_thread(), "not a Java thread");
798
799 // Threads shouldn't block if they are in the middle of printing, but...
800 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
801
802 // Only bail from the block() call if the thread is gone from the
803 // thread list; starting to exit should still block.
804 if (thread->is_terminated()) {
805 // block current thread if we come here from native code when VM is gone
806 thread->block_if_vm_exited();
807
808 // otherwise do nothing
809 return;
810 }
811
812 JavaThreadState state = thread->thread_state();
813 thread->frame_anchor()->make_walkable(thread);
814
815 // Check that we have a valid thread_state at this point
816 switch(state) {
817 case _thread_in_vm_trans:
818 case _thread_in_Java: // From compiled code
819
820 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
821 // we pretend we are still in the VM.
822 thread->set_thread_state(_thread_in_vm);
823
824 if (is_synchronizing()) {
825 Atomic::inc (&TryingToBlock) ;
826 }
827
828 // We will always be holding the Safepoint_lock when we are examine the state
829 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
830 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
831 Safepoint_lock->lock_without_safepoint_check();
832 if (is_synchronizing()) {
833 // Decrement the number of threads to wait for and signal vm thread
834 assert(_waiting_to_block > 0, "sanity check");
835 _waiting_to_block--;
836 thread->safepoint_state()->set_has_called_back(true);
837
838 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
839 if (thread->in_critical()) {
840 // Notice that this thread is in a critical section
841 increment_jni_active_count();
842 }
843
844 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
845 if (_waiting_to_block == 0) {
846 Safepoint_lock->notify_all();
847 }
848 }
849
850 // We transition the thread to state _thread_blocked here, but
851 // we can't do our usual check for external suspension and then
852 // self-suspend after the lock_without_safepoint_check() call
853 // below because we are often called during transitions while
854 // we hold different locks. That would leave us suspended while
855 // holding a resource which results in deadlocks.
856 thread->set_thread_state(_thread_blocked);
857 Safepoint_lock->unlock();
858
859 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
860 // the entire safepoint, the threads will all line up here during the safepoint.
861 Threads_lock->lock_without_safepoint_check();
862 // restore original state. This is important if the thread comes from compiled code, so it
863 // will continue to execute with the _thread_in_Java state.
864 thread->set_thread_state(state);
865 Threads_lock->unlock();
866 break;
867
868 case _thread_in_native_trans:
869 case _thread_blocked_trans:
870 case _thread_new_trans:
871 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
872 thread->print_thread_state();
873 fatal("Deadlock in safepoint code. "
874 "Should have called back to the VM before blocking.");
875 }
876
877 // We transition the thread to state _thread_blocked here, but
878 // we can't do our usual check for external suspension and then
879 // self-suspend after the lock_without_safepoint_check() call
880 // below because we are often called during transitions while
881 // we hold different locks. That would leave us suspended while
882 // holding a resource which results in deadlocks.
883 thread->set_thread_state(_thread_blocked);
884
885 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
886 // the safepoint code might still be waiting for it to block. We need to change the state here,
887 // so it can see that it is at a safepoint.
888
889 // Block until the safepoint operation is completed.
890 Threads_lock->lock_without_safepoint_check();
891
892 // Restore state
893 thread->set_thread_state(state);
894
895 Threads_lock->unlock();
896 break;
897
898 default:
899 fatal("Illegal threadstate encountered: %d", state);
900 }
901
902 // Check for pending. async. exceptions or suspends - except if the
903 // thread was blocked inside the VM. has_special_runtime_exit_condition()
904 // is called last since it grabs a lock and we only want to do that when
905 // we must.
906 //
907 // Note: we never deliver an async exception at a polling point as the
908 // compiler may not have an exception handler for it. The polling
909 // code will notice the async and deoptimize and the exception will
910 // be delivered. (Polling at a return point is ok though). Sure is
911 // a lot of bother for a deprecated feature...
912 //
913 // We don't deliver an async exception if the thread state is
914 // _thread_in_native_trans so JNI functions won't be called with
915 // a surprising pending exception. If the thread state is going back to java,
916 // async exception is checked in check_special_condition_for_native_trans().
917
918 if (state != _thread_blocked_trans &&
919 state != _thread_in_vm_trans &&
920 thread->has_special_runtime_exit_condition()) {
921 thread->handle_special_runtime_exit_condition(
922 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
923 }
924 }
925
926 // ------------------------------------------------------------------------------------------------------
927 // Exception handlers
928
929
930 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
931 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
932 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
933 if (!ThreadLocalHandshakes) {
934 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
935 }
936
937 if (log_is_enabled(Debug, safepoint, stats)) {
938 Atomic::inc(&_nof_threads_hit_polling_page);
939 }
940
941 ThreadSafepointState* state = thread->safepoint_state();
942
943 state->handle_polling_page_exception();
944 }
945
946
947 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
948 if (!timeout_error_printed) {
949 timeout_error_printed = true;
950 // Print out the thread info which didn't reach the safepoint for debugging
951 // purposes (useful when there are lots of threads in the debugger).
952 LogTarget(Warning, safepoint) lt;
953 if (lt.is_enabled()) {
954 ResourceMark rm;
955 LogStream ls(lt);
956
957 ls.cr();
958 ls.print_cr("# SafepointSynchronize::begin: Timeout detected:");
959 if (reason == _spinning_timeout) {
960 ls.print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
961 } else if (reason == _blocking_timeout) {
962 ls.print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
963 }
964
965 ls.print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
966 ThreadSafepointState *cur_state;
967 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) {
968 cur_state = cur_thread->safepoint_state();
969
970 if (cur_thread->thread_state() != _thread_blocked &&
971 ((reason == _spinning_timeout && cur_state->is_running()) ||
972 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
973 ls.print("# ");
974 cur_thread->print_on(&ls);
975 ls.cr();
976 }
977 }
978 ls.print_cr("# SafepointSynchronize::begin: (End of list)");
979 }
980 }
981
982 // To debug the long safepoint, specify both AbortVMOnSafepointTimeout &
983 // ShowMessageBoxOnError.
984 if (AbortVMOnSafepointTimeout) {
985 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
986 SafepointTimeoutDelay, VMThread::vm_safepoint_description());
987 }
988 }
989
990
991 // -------------------------------------------------------------------------------------------------------
992 // Implementation of ThreadSafepointState
993
994 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
995 _thread = thread;
996 _type = _running;
997 _has_called_back = false;
998 _at_poll_safepoint = false;
999 }
1000
1001 void ThreadSafepointState::create(JavaThread *thread) {
1002 ThreadSafepointState *state = new ThreadSafepointState(thread);
1003 thread->set_safepoint_state(state);
1004 }
1005
1006 void ThreadSafepointState::destroy(JavaThread *thread) {
1007 if (thread->safepoint_state()) {
1008 delete(thread->safepoint_state());
1009 thread->set_safepoint_state(NULL);
1010 }
1011 }
1012
1013 void ThreadSafepointState::examine_state_of_thread() {
1014 assert(is_running(), "better be running or just have hit safepoint poll");
1015
1016 JavaThreadState state = _thread->thread_state();
1017
1018 // Save the state at the start of safepoint processing.
1019 _orig_thread_state = state;
1020
1021 // Check for a thread that is suspended. Note that thread resume tries
1022 // to grab the Threads_lock which we own here, so a thread cannot be
1023 // resumed during safepoint synchronization.
1024
1025 // We check to see if this thread is suspended without locking to
1026 // avoid deadlocking with a third thread that is waiting for this
1027 // thread to be suspended. The third thread can notice the safepoint
1028 // that we're trying to start at the beginning of its SR_lock->wait()
1029 // call. If that happens, then the third thread will block on the
1030 // safepoint while still holding the underlying SR_lock. We won't be
1031 // able to get the SR_lock and we'll deadlock.
1032 //
1033 // We don't need to grab the SR_lock here for two reasons:
1034 // 1) The suspend flags are both volatile and are set with an
1035 // Atomic::cmpxchg() call so we should see the suspended
1036 // state right away.
1037 // 2) We're being called from the safepoint polling loop; if
1038 // we don't see the suspended state on this iteration, then
1039 // we'll come around again.
1040 //
1041 bool is_suspended = _thread->is_ext_suspended();
1042 if (is_suspended) {
1043 roll_forward(_at_safepoint);
1044 return;
1045 }
1046
1047 // Some JavaThread states have an initial safepoint state of
1048 // running, but are actually at a safepoint. We will happily
1049 // agree and update the safepoint state here.
1050 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
1051 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
1052 roll_forward(_at_safepoint);
1053 return;
1054 }
1055
1056 if (state == _thread_in_vm) {
1057 roll_forward(_call_back);
1058 return;
1059 }
1060
1061 // All other thread states will continue to run until they
1062 // transition and self-block in state _blocked
1063 // Safepoint polling in compiled code causes the Java threads to do the same.
1064 // Note: new threads may require a malloc so they must be allowed to finish
1065
1066 assert(is_running(), "examine_state_of_thread on non-running thread");
1067 return;
1068 }
1069
1070 // Returns true is thread could not be rolled forward at present position.
1071 void ThreadSafepointState::roll_forward(suspend_type type) {
1072 _type = type;
1073
1074 switch(_type) {
1075 case _at_safepoint:
1076 SafepointSynchronize::signal_thread_at_safepoint();
1077 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
1078 if (_thread->in_critical()) {
1079 // Notice that this thread is in a critical section
1080 SafepointSynchronize::increment_jni_active_count();
1081 }
1082 break;
1083
1084 case _call_back:
1085 set_has_called_back(false);
1086 break;
1087
1088 case _running:
1089 default:
1090 ShouldNotReachHere();
1091 }
1092 }
1093
1094 void ThreadSafepointState::restart() {
1095 switch(type()) {
1096 case _at_safepoint:
1097 case _call_back:
1098 break;
1099
1100 case _running:
1101 default:
1102 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
1103 p2i(_thread), _type);
1104 _thread->print();
1105 ShouldNotReachHere();
1106 }
1107 _type = _running;
1108 set_has_called_back(false);
1109 }
1110
1111
1112 void ThreadSafepointState::print_on(outputStream *st) const {
1113 const char *s = NULL;
1114
1115 switch(_type) {
1116 case _running : s = "_running"; break;
1117 case _at_safepoint : s = "_at_safepoint"; break;
1118 case _call_back : s = "_call_back"; break;
1119 default:
1120 ShouldNotReachHere();
1121 }
1122
1123 st->print_cr("Thread: " INTPTR_FORMAT
1124 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1125 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
1126 _at_poll_safepoint);
1127
1128 _thread->print_thread_state_on(st);
1129 }
1130
1131 // ---------------------------------------------------------------------------------------------------------------------
1132
1133 // Block the thread at poll or poll return for safepoint/handshake.
1134 void ThreadSafepointState::handle_polling_page_exception() {
1135
1136 // Check state. block() will set thread state to thread_in_vm which will
1137 // cause the safepoint state _type to become _call_back.
1138 suspend_type t = type();
1139 assert(!SafepointMechanism::uses_global_page_poll() || t == ThreadSafepointState::_running,
1140 "polling page exception on thread not running state: %u", uint(t));
1141
1142 // Step 1: Find the nmethod from the return address
1143 address real_return_addr = thread()->saved_exception_pc();
1144
1145 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1146 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1147 CompiledMethod* nm = (CompiledMethod*)cb;
1148
1149 // Find frame of caller
1150 frame stub_fr = thread()->last_frame();
1151 CodeBlob* stub_cb = stub_fr.cb();
1152 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1153 RegisterMap map(thread(), true);
1154 frame caller_fr = stub_fr.sender(&map);
1155
1156 // Should only be poll_return or poll
1157 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1158
1159 // This is a poll immediately before a return. The exception handling code
1160 // has already had the effect of causing the return to occur, so the execution
1161 // will continue immediately after the call. In addition, the oopmap at the
1162 // return point does not mark the return value as an oop (if it is), so
1163 // it needs a handle here to be updated.
1164 if( nm->is_at_poll_return(real_return_addr) ) {
1165 ResourceMark rm;
1166 // See if return type is an oop.
1167 Method* method = nm->method();
1168 bool return_oop = method->may_return_oop();
1169
1170 GrowableArray<Handle> return_values;
1171 ValueKlass* vk = NULL;
1172 if (method->is_returning_vt() && ValueTypeReturnedAsFields) {
1173 // Check if value type is returned as fields
1174 vk = ValueKlass::returned_value_klass(map);
1175 if (vk != NULL) {
1176 // We're at a safepoint at the return of a method that returns
1177 // multiple values. We must make sure we preserve the oop values
1178 // across the safepoint.
1179 assert(vk == method->returned_value_type(thread()), "bad value klass");
1180 vk->save_oop_fields(map, return_values);
1181 return_oop = false;
1182 }
1183 }
1184
1185 if (return_oop) {
1186 // The oop result has been saved on the stack together with all
1187 // the other registers. In order to preserve it over GCs we need
1188 // to keep it in a handle.
1189 oop result = caller_fr.saved_oop_result(&map);
1190 assert(oopDesc::is_oop_or_null(result), "must be oop");
1191 return_values.push(Handle(thread(), result));
1192 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1193 }
1194
1195 // Block the thread
1196 SafepointMechanism::block_if_requested(thread());
1197
1198 // restore oop result, if any
1199 if (return_oop) {
1200 assert(return_values.length() == 1, "only one return value");
1201 caller_fr.set_saved_oop_result(&map, return_values.pop()());
1202 } else if (vk != NULL) {
1203 vk->restore_oop_results(map, return_values);
1204 }
1205 }
1206
1207 // This is a safepoint poll. Verify the return address and block.
1208 else {
1209 set_at_poll_safepoint(true);
1210
1211 // verify the blob built the "return address" correctly
1212 assert(real_return_addr == caller_fr.pc(), "must match");
1213
1214 // Block the thread
1215 SafepointMechanism::block_if_requested(thread());
1216 set_at_poll_safepoint(false);
1217
1218 // If we have a pending async exception deoptimize the frame
1219 // as otherwise we may never deliver it.
1220 if (thread()->has_async_condition()) {
1221 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1222 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1223 }
1224
1225 // If an exception has been installed we must check for a pending deoptimization
1226 // Deoptimize frame if exception has been thrown.
1227
1228 if (thread()->has_pending_exception() ) {
1229 RegisterMap map(thread(), true);
1230 frame caller_fr = stub_fr.sender(&map);
1231 if (caller_fr.is_deoptimized_frame()) {
1232 // The exception patch will destroy registers that are still
1233 // live and will be needed during deoptimization. Defer the
1234 // Async exception should have deferred the exception until the
1235 // next safepoint which will be detected when we get into
1236 // the interpreter so if we have an exception now things
1237 // are messed up.
1238
1239 fatal("Exception installed and deoptimization is pending");
1240 }
1241 }
1242 }
1243 }
1244
1245
1246 //
1247 // Statistics & Instrumentations
1248 //
1249 struct SafepointStats {
1250 float _time_stamp; // record when the current safepoint occurs in seconds
1251 int _vmop_type; // tyep of VM operation triggers the safepoint
1252 int _nof_total_threads; // total number of Java threads
1253 int _nof_initial_running_threads; // total number of initially seen running threads
1254 int _nof_threads_wait_to_block; // total number of threads waiting for to block
1255 bool _page_armed; // true if polling page is armed, false otherwise
1256 int _nof_threads_hit_page_trap; // total number of threads hitting the page trap
1257 jlong _time_to_spin; // total time in millis spent in spinning
1258 jlong _time_to_wait_to_block; // total time in millis spent in waiting for to block
1259 jlong _time_to_do_cleanups; // total time in millis spent in performing cleanups
1260 jlong _time_to_sync; // total time in millis spent in getting to _synchronized
1261 jlong _time_to_exec_vmop; // total time in millis spent in vm operation itself
1262 };
1263
1264 static const int _statistics_header_count = 30;
1265 static int _cur_stat_index = 0;
1266 static SafepointStats safepoint_stats = {0}; // zero initialize
1267 static SafepointStats* spstat = &safepoint_stats;
1268
1269 static julong _safepoint_reasons[VM_Operation::VMOp_Terminating];
1270 static jlong _max_sync_time = 0;
1271 static jlong _max_vmop_time = 0;
1272
1273 static jlong cleanup_end_time = 0;
1274
1275 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1276
1277 spstat->_time_stamp = _ts_of_current_safepoint;
1278
1279 VM_Operation *op = VMThread::vm_operation();
1280 spstat->_vmop_type = op != NULL ? op->type() : VM_Operation::VMOp_None;
1281 _safepoint_reasons[spstat->_vmop_type]++;
1282
1283 spstat->_nof_total_threads = nof_threads;
1284 spstat->_nof_initial_running_threads = nof_running;
1285
1286 // Records the start time of spinning. The real time spent on spinning
1287 // will be adjusted when spin is done. Same trick is applied for time
1288 // spent on waiting for threads to block.
1289 if (nof_running != 0) {
1290 spstat->_time_to_spin = os::javaTimeNanos();
1291 } else {
1292 spstat->_time_to_spin = 0;
1293 }
1294 }
1295
1296 void SafepointSynchronize::update_statistics_on_spin_end() {
1297 jlong cur_time = os::javaTimeNanos();
1298
1299 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1300 if (spstat->_nof_initial_running_threads != 0) {
1301 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1302 }
1303
1304 // Records the start time of waiting for to block. Updated when block is done.
1305 if (_waiting_to_block != 0) {
1306 spstat->_time_to_wait_to_block = cur_time;
1307 } else {
1308 spstat->_time_to_wait_to_block = 0;
1309 }
1310 }
1311
1312 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1313
1314 if (spstat->_nof_threads_wait_to_block != 0) {
1315 spstat->_time_to_wait_to_block = end_time -
1316 spstat->_time_to_wait_to_block;
1317 }
1318
1319 // Records the end time of sync which will be used to calculate the total
1320 // vm operation time. Again, the real time spending in syncing will be deducted
1321 // from the start of the sync time later when end_statistics is called.
1322 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1323 if (spstat->_time_to_sync > _max_sync_time) {
1324 _max_sync_time = spstat->_time_to_sync;
1325 }
1326
1327 spstat->_time_to_do_cleanups = end_time;
1328 }
1329
1330 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1331
1332 // Record how long spent in cleanup tasks.
1333 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1334 cleanup_end_time = end_time;
1335 }
1336
1337 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1338
1339 // Update the vm operation time.
1340 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1341 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1342 _max_vmop_time = spstat->_time_to_exec_vmop;
1343 }
1344
1345 spstat->_nof_threads_hit_page_trap = _nof_threads_hit_polling_page;
1346
1347 print_statistics();
1348 }
1349
1350 // Helper method to print the header.
1351 static void print_header(outputStream* st) {
1352 // The number of spaces is significant here, and should match the format
1353 // specifiers in print_statistics().
1354
1355 st->print(" vmop "
1356 "[ threads: total initially_running wait_to_block ]"
1357 "[ time: spin block sync cleanup vmop ] ");
1358
1359 st->print_cr("page_trap_count");
1360 }
1361
1362 // This prints a nice table. To get the statistics to not shift due to the logging uptime
1363 // decorator, use the option as: -Xlog:safepoint+stats=debug:[outputfile]:none
1364 void SafepointSynchronize::print_statistics() {
1365 LogTarget(Debug, safepoint, stats) lt;
1366 assert (lt.is_enabled(), "should only be called when printing statistics is enabled");
1367 LogStream ls(lt);
1368
1369 // Print header every 30 entries
1370 if ((_cur_stat_index % _statistics_header_count) == 0) {
1371 print_header(&ls);
1372 _cur_stat_index = 1; // wrap
1373 } else {
1374 _cur_stat_index++;
1375 }
1376
1377 ls.print("%8.3f: ", spstat->_time_stamp);
1378 ls.print("%-28s [ "
1379 INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " "
1380 "]",
1381 VM_Operation::name(spstat->_vmop_type),
1382 spstat->_nof_total_threads,
1383 spstat->_nof_initial_running_threads,
1384 spstat->_nof_threads_wait_to_block);
1385 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1386 ls.print("[ "
1387 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1388 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1389 INT64_FORMAT_W(7) " ] ",
1390 (int64_t)(spstat->_time_to_spin / MICROUNITS),
1391 (int64_t)(spstat->_time_to_wait_to_block / MICROUNITS),
1392 (int64_t)(spstat->_time_to_sync / MICROUNITS),
1393 (int64_t)(spstat->_time_to_do_cleanups / MICROUNITS),
1394 (int64_t)(spstat->_time_to_exec_vmop / MICROUNITS));
1395
1396 ls.print_cr(INT32_FORMAT_W(15) " ", spstat->_nof_threads_hit_page_trap);
1397 }
1398
1399 // This method will be called when VM exits. This tries to summarize the sampling.
1400 // Current thread may already be deleted, so don't use ResourceMark.
1401 void SafepointSynchronize::print_stat_on_exit() {
1402
1403 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1404 if (_safepoint_reasons[index] != 0) {
1405 log_debug(safepoint, stats)("%-28s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1406 _safepoint_reasons[index]);
1407 }
1408 }
1409
1410 log_debug(safepoint, stats)("VM operations coalesced during safepoint " INT64_FORMAT,
1411 _coalesced_vmop_count);
1412 log_debug(safepoint, stats)("Maximum sync time " INT64_FORMAT" ms",
1413 (int64_t)(_max_sync_time / MICROUNITS));
1414 log_debug(safepoint, stats)("Maximum vm operation time (except for Exit VM operation) "
1415 INT64_FORMAT " ms",
1416 (int64_t)(_max_vmop_time / MICROUNITS));
1417 }