1 /*
2 * Copyright (c) 1997, 2019, 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 "runtime/atomic.hpp"
48 #include "runtime/compilationPolicy.hpp"
49 #include "runtime/deoptimization.hpp"
50 #include "runtime/frame.inline.hpp"
51 #include "runtime/handles.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 static void post_safepoint_begin_event(EventSafepointBegin& event,
74 uint64_t safepoint_id,
75 int thread_count,
76 int critical_thread_count) {
77 if (event.should_commit()) {
78 event.set_safepointId(safepoint_id);
79 event.set_totalThreadCount(thread_count);
80 event.set_jniCriticalThreadCount(critical_thread_count);
81 event.commit();
82 }
83 }
84
85 static void post_safepoint_cleanup_event(EventSafepointCleanup& event, uint64_t safepoint_id) {
86 if (event.should_commit()) {
87 event.set_safepointId(safepoint_id);
88 event.commit();
89 }
90 }
91
92 static void post_safepoint_synchronize_event(EventSafepointStateSynchronization& event,
93 uint64_t safepoint_id,
94 int initial_number_of_threads,
95 int threads_waiting_to_block,
96 uint64_t iterations) {
97 if (event.should_commit()) {
98 event.set_safepointId(safepoint_id);
99 event.set_initialThreadCount(initial_number_of_threads);
100 event.set_runningThreadCount(threads_waiting_to_block);
101 event.set_iterations(iterations);
102 event.commit();
103 }
104 }
105
106 static void post_safepoint_cleanup_task_event(EventSafepointCleanupTask& event,
107 uint64_t safepoint_id,
108 const char* name) {
109 if (event.should_commit()) {
110 event.set_safepointId(safepoint_id);
111 event.set_name(name);
112 event.commit();
113 }
114 }
115
116 static void post_safepoint_end_event(EventSafepointEnd& event, uint64_t safepoint_id) {
117 if (event.should_commit()) {
118 event.set_safepointId(safepoint_id);
119 event.commit();
120 }
121 }
122
123 // --------------------------------------------------------------------------------------------------
124 // Implementation of Safepoint begin/end
125
126 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
127 int SafepointSynchronize::_waiting_to_block = 0;
128 volatile uint64_t SafepointSynchronize::_safepoint_counter = 0;
129 const uint64_t SafepointSynchronize::InactiveSafepointCounter = 0;
130 int SafepointSynchronize::_current_jni_active_count = 0;
131
132 WaitBarrier* SafepointSynchronize::_wait_barrier;
133
134 static volatile bool PageArmed = false; // safepoint polling page is RO|RW vs PROT_NONE
135 static bool timeout_error_printed = false;
136
137 // Statistic related
138 static jlong _safepoint_begin_time = 0;
139 static volatile int _nof_threads_hit_polling_page = 0;
140
141 void SafepointSynchronize::init(Thread* vmthread) {
142 // WaitBarrier should never be destroyed since we will have
143 // threads waiting on it while exiting.
144 _wait_barrier = new WaitBarrier(vmthread);
145 SafepointTracing::init();
146 }
147
148 void SafepointSynchronize::increment_jni_active_count() {
149 assert(Thread::current()->is_VM_thread(), "Only VM thread may increment");
150 ++_current_jni_active_count;
151 }
152
153 void SafepointSynchronize::decrement_waiting_to_block() {
154 assert(_waiting_to_block > 0, "sanity check");
155 assert(Thread::current()->is_VM_thread(), "Only VM thread may decrement");
156 --_waiting_to_block;
157 }
158
159 static bool thread_not_running(ThreadSafepointState *cur_state) {
160 if (!cur_state->is_running()) {
161 return true;
162 }
163 cur_state->examine_state_of_thread(SafepointSynchronize::safepoint_counter());
164 if (!cur_state->is_running()) {
165 return true;
166 }
167 LogTarget(Trace, safepoint) lt;
168 if (lt.is_enabled()) {
169 ResourceMark rm;
170 LogStream ls(lt);
171 cur_state->print_on(&ls);
172 }
173 return false;
174 }
175
176 #ifdef ASSERT
177 static void assert_list_is_valid(const ThreadSafepointState* tss_head, int still_running) {
178 int a = 0;
179 const ThreadSafepointState *tmp_tss = tss_head;
180 while (tmp_tss != NULL) {
181 ++a;
182 assert(tmp_tss->is_running(), "Illegal initial state");
183 tmp_tss = tmp_tss->get_next();
184 }
185 assert(a == still_running, "Must be the same");
186 }
187 #endif // ASSERT
188
189 static void back_off(int iteration) {
190 // iteration will be 1 the first time we enter this spin back-off.
191 // naked_short_nanosleep takes tenths of micros which means that
192 // number of nanoseconds is irrelevant if it's below that. We do
193 // 20 1 ns sleeps with a total cost of ~1 ms, then we do 1 ms sleeps.
194 jlong sleep_ns = 1;
195 if (iteration > 20) {
196 sleep_ns = NANOUNITS / MILLIUNITS; // 1 ms
197 }
198 os::naked_short_nanosleep(sleep_ns);
199 }
200
201 int SafepointSynchronize::synchronize_threads(jlong safepoint_limit_time, int nof_threads, int* initial_running)
202 {
203 JavaThreadIteratorWithHandle jtiwh;
204
205 #ifdef ASSERT
206 for (; JavaThread *cur = jtiwh.next(); ) {
207 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
208 }
209 jtiwh.rewind();
210 #endif // ASSERT
211
212 // Iterate through all threads until it has been determined how to stop them all at a safepoint.
213 int still_running = nof_threads;
214 ThreadSafepointState *tss_head = NULL;
215 ThreadSafepointState **p_prev = &tss_head;
216 for (; JavaThread *cur = jtiwh.next(); ) {
217 ThreadSafepointState *cur_tss = cur->safepoint_state();
218 assert(cur_tss->get_next() == NULL, "Must be NULL");
219 if (thread_not_running(cur_tss)) {
220 --still_running;
221 } else {
222 *p_prev = cur_tss;
223 p_prev = cur_tss->next_ptr();
224 }
225 }
226 *p_prev = NULL;
227
228 DEBUG_ONLY(assert_list_is_valid(tss_head, still_running);)
229
230 *initial_running = still_running;
231
232 int iterations = 1; // The first iteration is above.
233
234 while (still_running > 0) {
235 // Check if this has taken too long:
236 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
237 print_safepoint_timeout();
238 }
239 if (int(iterations) == -1) { // overflow - something is wrong.
240 // We can only overflow here when we are using global
241 // polling pages. We keep this guarantee in its original
242 // form so that searches of the bug database for this
243 // failure mode find the right bugs.
244 guarantee (!PageArmed, "invariant");
245 }
246
247 p_prev = &tss_head;
248 ThreadSafepointState *cur_tss = tss_head;
249 while (cur_tss != NULL) {
250 assert(cur_tss->is_running(), "Illegal initial state");
251 if (thread_not_running(cur_tss)) {
252 --still_running;
253 *p_prev = NULL;
254 ThreadSafepointState *tmp = cur_tss;
255 cur_tss = cur_tss->get_next();
256 tmp->set_next(NULL);
257 } else {
258 *p_prev = cur_tss;
259 p_prev = cur_tss->next_ptr();
260 cur_tss = cur_tss->get_next();
261 }
262 }
263
264 DEBUG_ONLY(assert_list_is_valid(tss_head, still_running);)
265
266 if (still_running > 0) {
267 back_off(iterations);
268 }
269
270 iterations++;
271 }
272
273 assert(tss_head == NULL, "Must be empty");
274
275 return iterations;
276 }
277
278 void SafepointSynchronize::arm_safepoint() {
279 // Begin the process of bringing the system to a safepoint.
280 // Java threads can be in several different states and are
281 // stopped by different mechanisms:
282 //
283 // 1. Running interpreted
284 // When executing branching/returning byte codes interpreter
285 // checks if the poll is armed, if so blocks in SS::block().
286 // When using global polling the interpreter dispatch table
287 // is changed to force it to check for a safepoint condition
288 // between bytecodes.
289 // 2. Running in native code
290 // When returning from the native code, a Java thread must check
291 // the safepoint _state to see if we must block. If the
292 // VM thread sees a Java thread in native, it does
293 // not wait for this thread to block. The order of the memory
294 // writes and reads of both the safepoint state and the Java
295 // threads state is critical. In order to guarantee that the
296 // memory writes are serialized with respect to each other,
297 // the VM thread issues a memory barrier instruction.
298 // 3. Running compiled Code
299 // Compiled code reads the local polling page that
300 // is set to fault if we are trying to get to a safepoint.
301 // 4. Blocked
302 // A thread which is blocked will not be allowed to return from the
303 // block condition until the safepoint operation is complete.
304 // 5. In VM or Transitioning between states
305 // If a Java thread is currently running in the VM or transitioning
306 // between states, the safepointing code will poll the thread state
307 // until the thread blocks itself when it attempts transitions to a
308 // new state or locking a safepoint checked monitor.
309
310 // We must never miss a thread with correct safepoint id, so we must make sure we arm
311 // the wait barrier for the next safepoint id/counter.
312 // Arming must be done after resetting _current_jni_active_count, _waiting_to_block.
313 _wait_barrier->arm(static_cast<int>(_safepoint_counter + 1));
314
315 assert((_safepoint_counter & 0x1) == 0, "must be even");
316 // The store to _safepoint_counter must happen after any stores in arming.
317 OrderAccess::release_store(&_safepoint_counter, _safepoint_counter + 1);
318
319 // We are synchronizing
320 OrderAccess::storestore(); // Ordered with _safepoint_counter
321 _state = _synchronizing;
322
323 if (SafepointMechanism::uses_thread_local_poll()) {
324 // Arming the per thread poll while having _state != _not_synchronized means safepointing
325 log_trace(safepoint)("Setting thread local yield flag for threads");
326 OrderAccess::storestore(); // storestore, global state -> local state
327 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
328 // Make sure the threads start polling, it is time to yield.
329 SafepointMechanism::arm_local_poll(cur);
330 }
331 }
332 OrderAccess::fence(); // storestore|storeload, global state -> local state
333
334 if (SafepointMechanism::uses_global_page_poll()) {
335 // Make interpreter safepoint aware
336 Interpreter::notice_safepoints();
337
338 // Make polling safepoint aware
339 guarantee (!PageArmed, "invariant") ;
340 PageArmed = true;
341 os::make_polling_page_unreadable();
342 }
343 }
344
345 // Roll all threads forward to a safepoint and suspend them all
346 void SafepointSynchronize::begin() {
347 assert(Thread::current()->is_VM_thread(), "Only VM thread may execute a safepoint");
348
349 EventSafepointBegin begin_event;
350 SafepointTracing::begin(VMThread::vm_op_type());
351
352 Universe::heap()->safepoint_synchronize_begin();
353
354 // By getting the Threads_lock, we assure that no threads are about to start or
355 // exit. It is released again in SafepointSynchronize::end().
356 Threads_lock->lock();
357
358 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
359
360 int nof_threads = Threads::number_of_threads();
361
362 _nof_threads_hit_polling_page = 0;
363
364 log_debug(safepoint)("Safepoint synchronization initiated using %s wait barrier. (%d threads)", _wait_barrier->description(), nof_threads);
365
366 // Reset the count of active JNI critical threads
367 _current_jni_active_count = 0;
368
369 // Set number of threads to wait for
370 _waiting_to_block = nof_threads;
371
372 jlong safepoint_limit_time = 0;
373 if (SafepointTimeout) {
374 // Set the limit time, so that it can be compared to see if this has taken
375 // too long to complete.
376 safepoint_limit_time = SafepointTracing::start_of_safepoint() + (jlong)SafepointTimeoutDelay * (NANOUNITS / MILLIUNITS);
377 timeout_error_printed = false;
378 }
379
380 EventSafepointStateSynchronization sync_event;
381 int initial_running = 0;
382
383 // Arms the safepoint, _current_jni_active_count and _waiting_to_block must be set before.
384 arm_safepoint();
385
386 // Will spin until all threads are safe.
387 int iterations = synchronize_threads(safepoint_limit_time, nof_threads, &initial_running);
388 assert(_waiting_to_block == 0, "No thread should be running");
389
390 #ifndef PRODUCT
391 if (safepoint_limit_time != 0) {
392 jlong current_time = os::javaTimeNanos();
393 if (safepoint_limit_time < current_time) {
394 log_warning(safepoint)("# SafepointSynchronize: Finished after "
395 INT64_FORMAT_W(6) " ms",
396 (int64_t)(current_time - SafepointTracing::start_of_safepoint()) / (NANOUNITS / MILLIUNITS));
397 }
398 }
399 #endif
400
401 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
402
403 // Record state
404 _state = _synchronized;
405
406 OrderAccess::fence();
407
408 #ifdef ASSERT
409 // Make sure all the threads were visited.
410 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
411 assert(cur->was_visited_for_critical_count(_safepoint_counter), "missed a thread");
412 }
413 #endif // ASSERT
414
415 // Update the count of active JNI critical regions
416 GCLocker::set_jni_lock_count(_current_jni_active_count);
417
418 post_safepoint_synchronize_event(sync_event,
419 _safepoint_counter,
420 initial_running,
421 _waiting_to_block, iterations);
422
423 SafepointTracing::synchronized(nof_threads, initial_running, _nof_threads_hit_polling_page);
424
425 // We do the safepoint cleanup first since a GC related safepoint
426 // needs cleanup to be completed before running the GC op.
427 EventSafepointCleanup cleanup_event;
428 do_cleanup_tasks();
429 post_safepoint_cleanup_event(cleanup_event, _safepoint_counter);
430
431 post_safepoint_begin_event(begin_event, _safepoint_counter, nof_threads, _current_jni_active_count);
432 SafepointTracing::cleanup();
433 }
434
435 void SafepointSynchronize::disarm_safepoint() {
436 uint64_t safepoint_id = _safepoint_counter;
437 {
438 JavaThreadIteratorWithHandle jtiwh;
439 #ifdef ASSERT
440 // A pending_exception cannot be installed during a safepoint. The threads
441 // may install an async exception after they come back from a safepoint into
442 // pending_exception after they unblock. But that should happen later.
443 for (; JavaThread *cur = jtiwh.next(); ) {
444 assert (!(cur->has_pending_exception() &&
445 cur->safepoint_state()->is_at_poll_safepoint()),
446 "safepoint installed a pending exception");
447 }
448 #endif // ASSERT
449
450 if (SafepointMechanism::uses_global_page_poll()) {
451 guarantee (PageArmed, "invariant");
452 // Make polling safepoint aware
453 os::make_polling_page_readable();
454 PageArmed = false;
455 // Remove safepoint check from interpreter
456 Interpreter::ignore_safepoints();
457 }
458
459 OrderAccess::fence(); // keep read and write of _state from floating up
460 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
461
462 // Change state first to _not_synchronized.
463 // No threads should see _synchronized when running.
464 _state = _not_synchronized;
465
466 // Set the next dormant (even) safepoint id.
467 assert((_safepoint_counter & 0x1) == 1, "must be odd");
468 OrderAccess::release_store(&_safepoint_counter, _safepoint_counter + 1);
469
470 OrderAccess::fence(); // Keep the local state from floating up.
471
472 jtiwh.rewind();
473 for (; JavaThread *current = jtiwh.next(); ) {
474 // Clear the visited flag to ensure that the critical counts are collected properly.
475 DEBUG_ONLY(current->reset_visited_for_critical_count(safepoint_id);)
476 ThreadSafepointState* cur_state = current->safepoint_state();
477 assert(!cur_state->is_running(), "Thread not suspended at safepoint");
478 cur_state->restart(); // TSS _running
479 assert(cur_state->is_running(), "safepoint state has not been reset");
480 SafepointMechanism::disarm_local_poll(current);
481 }
482 } // ~JavaThreadIteratorWithHandle
483
484 // Release threads lock, so threads can be created/destroyed again.
485 Threads_lock->unlock();
486
487 // Wake threads after local state is correctly set.
488 _wait_barrier->disarm();
489 }
490
491 // Wake up all threads, so they are ready to resume execution after the safepoint
492 // operation has been carried out
493 void SafepointSynchronize::end() {
494 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
495 EventSafepointEnd event;
496 uint64_t safepoint_id = _safepoint_counter;
497 assert(Thread::current()->is_VM_thread(), "Only VM thread can execute a safepoint");
498
499 disarm_safepoint();
500
501 Universe::heap()->safepoint_synchronize_end();
502
503 SafepointTracing::end();
504
505 post_safepoint_end_event(event, safepoint_id);
506 }
507
508 bool SafepointSynchronize::is_cleanup_needed() {
509 // Need a safepoint if there are many monitors to deflate.
510 if (ObjectSynchronizer::is_cleanup_needed()) return true;
511 // Need a safepoint if some inline cache buffers is non-empty
512 if (!InlineCacheBuffer::is_empty()) return true;
513 return false;
514 }
515
516 class ParallelSPCleanupThreadClosure : public ThreadClosure {
517 private:
518 CodeBlobClosure* _nmethod_cl;
519 DeflateMonitorCounters* _counters;
520
521 public:
522 ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) :
523 _nmethod_cl(UseCodeAging ? NMethodSweeper::prepare_reset_hotness_counters() : NULL),
524 _counters(counters) {}
525
526 void do_thread(Thread* thread) {
527 ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters);
528 if (_nmethod_cl != NULL && thread->is_Java_thread() &&
529 ! thread->is_Code_cache_sweeper_thread()) {
530 JavaThread* jt = (JavaThread*) thread;
531 jt->nmethods_do(_nmethod_cl);
532 }
533 }
534 };
535
536 class ParallelSPCleanupTask : public AbstractGangTask {
537 private:
538 SubTasksDone _subtasks;
539 ParallelSPCleanupThreadClosure _cleanup_threads_cl;
540 uint _num_workers;
541 DeflateMonitorCounters* _counters;
542 public:
543 ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
544 AbstractGangTask("Parallel Safepoint Cleanup"),
545 _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)),
546 _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
547 _num_workers(num_workers),
548 _counters(counters) {}
549
550 void work(uint worker_id) {
551 uint64_t safepoint_id = SafepointSynchronize::safepoint_counter();
552 // All threads deflate monitors and mark nmethods (if necessary).
553 Threads::possibly_parallel_threads_do(true, &_cleanup_threads_cl);
554
555 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
556 const char* name = "deflating global idle monitors";
557 EventSafepointCleanupTask event;
558 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
559 // AsyncDeflateIdleMonitors only uses DeflateMonitorCounters
560 // when a special cleanup has been requested.
561 // Note: This logging output will include global idle monitor
562 // elapsed times, but not global idle monitor deflation count.
563 ObjectSynchronizer::do_safepoint_work(!AsyncDeflateIdleMonitors ? _counters : NULL);
564
565 post_safepoint_cleanup_task_event(event, safepoint_id, name);
566 }
567
568 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
569 const char* name = "updating inline caches";
570 EventSafepointCleanupTask event;
571 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
572 InlineCacheBuffer::update_inline_caches();
573
574 post_safepoint_cleanup_task_event(event, safepoint_id, name);
575 }
576
577 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
578 const char* name = "compilation policy safepoint handler";
579 EventSafepointCleanupTask event;
580 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
581 CompilationPolicy::policy()->do_safepoint_work();
582
583 post_safepoint_cleanup_task_event(event, safepoint_id, name);
584 }
585
586 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
587 if (SymbolTable::needs_rehashing()) {
588 const char* name = "rehashing symbol table";
589 EventSafepointCleanupTask event;
590 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
591 SymbolTable::rehash_table();
592
593 post_safepoint_cleanup_task_event(event, safepoint_id, name);
594 }
595 }
596
597 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
598 if (StringTable::needs_rehashing()) {
599 const char* name = "rehashing string table";
600 EventSafepointCleanupTask event;
601 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
602 StringTable::rehash_table();
603
604 post_safepoint_cleanup_task_event(event, safepoint_id, name);
605 }
606 }
607
608 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) {
609 // CMS delays purging the CLDG until the beginning of the next safepoint and to
610 // make sure concurrent sweep is done
611 const char* name = "purging class loader data graph";
612 EventSafepointCleanupTask event;
613 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
614 ClassLoaderDataGraph::purge_if_needed();
615
616 post_safepoint_cleanup_task_event(event, safepoint_id, name);
617 }
618
619 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_SYSTEM_DICTIONARY_RESIZE)) {
620 const char* name = "resizing system dictionaries";
621 EventSafepointCleanupTask event;
622 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
623 ClassLoaderDataGraph::resize_if_needed();
624
625 post_safepoint_cleanup_task_event(event, safepoint_id, name);
626 }
627
628 _subtasks.all_tasks_completed(_num_workers);
629 }
630 };
631
632 // Various cleaning tasks that should be done periodically at safepoints.
633 void SafepointSynchronize::do_cleanup_tasks() {
634
635 TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup));
636
637 // Prepare for monitor deflation.
638 DeflateMonitorCounters deflate_counters;
639 ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
640
641 CollectedHeap* heap = Universe::heap();
642 assert(heap != NULL, "heap not initialized yet?");
643 WorkGang* cleanup_workers = heap->get_safepoint_workers();
644 if (cleanup_workers != NULL) {
645 // Parallel cleanup using GC provided thread pool.
646 uint num_cleanup_workers = cleanup_workers->active_workers();
647 ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
648 StrongRootsScope srs(num_cleanup_workers);
649 cleanup_workers->run_task(&cleanup);
650 } else {
651 // Serial cleanup using VMThread.
652 ParallelSPCleanupTask cleanup(1, &deflate_counters);
653 StrongRootsScope srs(1);
654 cleanup.work(0);
655 }
656
657 // Needs to be done single threaded by the VMThread. This walks
658 // the thread stacks looking for references to metadata before
659 // deciding to remove it from the metaspaces.
660 if (ClassLoaderDataGraph::should_clean_metaspaces_and_reset()) {
661 const char* name = "cleanup live ClassLoaderData metaspaces";
662 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
663 ClassLoaderDataGraph::walk_metadata_and_clean_metaspaces();
664 }
665
666 // Finish monitor deflation.
667 ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
668
669 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
670 }
671
672 // Methods for determining if a JavaThread is safepoint safe.
673
674 // False means unsafe with undetermined state.
675 // True means a determined state, but it may be an unsafe state.
676 // If called from a non-safepoint context safepoint_count MUST be InactiveSafepointCounter.
677 bool SafepointSynchronize::try_stable_load_state(JavaThreadState *state, JavaThread *thread, uint64_t safepoint_count) {
678 assert((safepoint_count != InactiveSafepointCounter &&
679 Thread::current() == (Thread*)VMThread::vm_thread() &&
680 SafepointSynchronize::_state != _not_synchronized)
681 || safepoint_count == InactiveSafepointCounter, "Invalid check");
682
683 // To handle the thread_blocked state on the backedge of the WaitBarrier from
684 // previous safepoint and reading the reset value (0/InactiveSafepointCounter) we
685 // re-read state after we read thread safepoint id. The JavaThread changes its
686 // thread state from thread_blocked before resetting safepoint id to 0.
687 // This guarantees the second read will be from an updated thread state. It can
688 // either be different state making this an unsafe state or it can see blocked
689 // again. When we see blocked twice with a 0 safepoint id, either:
690 // - It is normally blocked, e.g. on Mutex, TBIVM.
691 // - It was in SS:block(), looped around to SS:block() and is blocked on the WaitBarrier.
692 // - It was in SS:block() but now on a Mutex.
693 // All of these cases are safe.
694
695 *state = thread->thread_state();
696 OrderAccess::loadload();
697 uint64_t sid = thread->safepoint_state()->get_safepoint_id(); // Load acquire
698 if (sid != InactiveSafepointCounter && sid != safepoint_count) {
699 // In an old safepoint, state not relevant.
700 return false;
701 }
702 return *state == thread->thread_state();
703 }
704
705 static bool safepoint_safe_with(JavaThread *thread, JavaThreadState state) {
706 switch(state) {
707 case _thread_in_native:
708 // native threads are safe if they have no java stack or have walkable stack
709 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
710
711 case _thread_blocked:
712 // On wait_barrier or blocked.
713 // Blocked threads should already have walkable stack.
714 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
715 return true;
716
717 default:
718 return false;
719 }
720 }
721
722 bool SafepointSynchronize::handshake_safe(JavaThread *thread) {
723 // The polls must be armed otherwise the safe state can change to unsafe at any time.
724 assert(SafepointMechanism::should_block(thread), "Must be armed");
725 // This function must be called with the Threads_lock held so an externally
726 // suspended thread cannot be resumed thus it is safe.
727 assert(Threads_lock->owned_by_self() && Thread::current()->is_VM_thread(),
728 "Must hold Threads_lock and be VMThread");
729 if (thread->is_ext_suspended() || thread->is_terminated()) {
730 return true;
731 }
732 JavaThreadState stable_state;
733 if (try_stable_load_state(&stable_state, thread, InactiveSafepointCounter)) {
734 return safepoint_safe_with(thread, stable_state);
735 }
736 return false;
737 }
738
739 // See if the thread is running inside a lazy critical native and
740 // update the thread critical count if so. Also set a suspend flag to
741 // cause the native wrapper to return into the JVM to do the unlock
742 // once the native finishes.
743 static void check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
744 if (state == _thread_in_native &&
745 thread->has_last_Java_frame() &&
746 thread->frame_anchor()->walkable()) {
747 // This thread might be in a critical native nmethod so look at
748 // the top of the stack and increment the critical count if it
749 // is.
750 frame wrapper_frame = thread->last_frame();
751 CodeBlob* stub_cb = wrapper_frame.cb();
752 if (stub_cb != NULL &&
753 stub_cb->is_nmethod() &&
754 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
755 // A thread could potentially be in a critical native across
756 // more than one safepoint, so only update the critical state on
757 // the first one. When it returns it will perform the unlock.
758 if (!thread->do_critical_native_unlock()) {
759 #ifdef ASSERT
760 if (!thread->in_critical()) {
761 GCLocker::increment_debug_jni_lock_count();
762 }
763 #endif
764 thread->enter_critical();
765 // Make sure the native wrapper calls back on return to
766 // perform the needed critical unlock.
767 thread->set_critical_native_unlock();
768 }
769 }
770 }
771 }
772
773 // -------------------------------------------------------------------------------------------------------
774 // Implementation of Safepoint blocking point
775
776 void SafepointSynchronize::block(JavaThread *thread) {
777 assert(thread != NULL, "thread must be set");
778 assert(thread->is_Java_thread(), "not a Java thread");
779
780 // Threads shouldn't block if they are in the middle of printing, but...
781 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
782
783 // Only bail from the block() call if the thread is gone from the
784 // thread list; starting to exit should still block.
785 if (thread->is_terminated()) {
786 // block current thread if we come here from native code when VM is gone
787 thread->block_if_vm_exited();
788
789 // otherwise do nothing
790 return;
791 }
792
793 JavaThreadState state = thread->thread_state();
794 thread->frame_anchor()->make_walkable(thread);
795
796 uint64_t safepoint_id = SafepointSynchronize::safepoint_counter();
797 // Check that we have a valid thread_state at this point
798 switch(state) {
799 case _thread_in_vm_trans:
800 case _thread_in_Java: // From compiled code
801 case _thread_in_native_trans:
802 case _thread_blocked_trans:
803 case _thread_new_trans:
804
805 // We have no idea where the VMThread is, it might even be at next safepoint.
806 // So we can miss this poll, but stop at next.
807
808 // Load dependent store, it must not pass loading of safepoint_id.
809 thread->safepoint_state()->set_safepoint_id(safepoint_id); // Release store
810
811 // This part we can skip if we notice we miss or are in a future safepoint.
812 OrderAccess::storestore();
813 thread->set_thread_state(_thread_blocked);
814
815 OrderAccess::fence(); // Load in wait barrier should not float up
816 _wait_barrier->wait(static_cast<int>(safepoint_id));
817 assert(_state != _synchronized, "Can't be");
818
819 // If barrier is disarmed stop store from floating above loads in barrier.
820 OrderAccess::loadstore();
821 thread->set_thread_state(state);
822
823 // Then we reset the safepoint id to inactive.
824 thread->safepoint_state()->reset_safepoint_id(); // Release store
825
826 OrderAccess::fence();
827
828 break;
829
830 default:
831 fatal("Illegal threadstate encountered: %d", state);
832 }
833 guarantee(thread->safepoint_state()->get_safepoint_id() == InactiveSafepointCounter,
834 "The safepoint id should be set only in block path");
835
836 // Check for pending. async. exceptions or suspends - except if the
837 // thread was blocked inside the VM. has_special_runtime_exit_condition()
838 // is called last since it grabs a lock and we only want to do that when
839 // we must.
840 //
841 // Note: we never deliver an async exception at a polling point as the
842 // compiler may not have an exception handler for it. The polling
843 // code will notice the async and deoptimize and the exception will
844 // be delivered. (Polling at a return point is ok though). Sure is
845 // a lot of bother for a deprecated feature...
846 //
847 // We don't deliver an async exception if the thread state is
848 // _thread_in_native_trans so JNI functions won't be called with
849 // a surprising pending exception. If the thread state is going back to java,
850 // async exception is checked in check_special_condition_for_native_trans().
851
852 if (state != _thread_blocked_trans &&
853 state != _thread_in_vm_trans &&
854 thread->has_special_runtime_exit_condition()) {
855 thread->handle_special_runtime_exit_condition(
856 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
857 }
858 }
859
860 // ------------------------------------------------------------------------------------------------------
861 // Exception handlers
862
863
864 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
865 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
866 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
867 if (!ThreadLocalHandshakes) {
868 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
869 }
870
871 if (log_is_enabled(Info, safepoint, stats)) {
872 Atomic::inc(&_nof_threads_hit_polling_page);
873 }
874
875 ThreadSafepointState* state = thread->safepoint_state();
876
877 state->handle_polling_page_exception();
878 }
879
880
881 void SafepointSynchronize::print_safepoint_timeout() {
882 if (!timeout_error_printed) {
883 timeout_error_printed = true;
884 // Print out the thread info which didn't reach the safepoint for debugging
885 // purposes (useful when there are lots of threads in the debugger).
886 LogTarget(Warning, safepoint) lt;
887 if (lt.is_enabled()) {
888 ResourceMark rm;
889 LogStream ls(lt);
890
891 ls.cr();
892 ls.print_cr("# SafepointSynchronize::begin: Timeout detected:");
893 ls.print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
894 ls.print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
895 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) {
896 if (cur_thread->safepoint_state()->is_running()) {
897 ls.print("# ");
898 cur_thread->print_on(&ls);
899 ls.cr();
900 }
901 }
902 ls.print_cr("# SafepointSynchronize::begin: (End of list)");
903 }
904 }
905
906 // To debug the long safepoint, specify both AbortVMOnSafepointTimeout &
907 // ShowMessageBoxOnError.
908 if (AbortVMOnSafepointTimeout) {
909 // Send the blocking thread a signal to terminate and write an error file.
910 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) {
911 if (cur_thread->safepoint_state()->is_running()) {
912 if (!os::signal_thread(cur_thread, SIGILL, "blocking a safepoint")) {
913 break; // Could not send signal. Report fatal error.
914 }
915 // Give cur_thread a chance to report the error and terminate the VM.
916 os::sleep(Thread::current(), 3000, false);
917 }
918 }
919 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
920 SafepointTimeoutDelay, VMThread::vm_operation()->name());
921 }
922 }
923
924 // -------------------------------------------------------------------------------------------------------
925 // Implementation of ThreadSafepointState
926
927 ThreadSafepointState::ThreadSafepointState(JavaThread *thread)
928 : _at_poll_safepoint(false), _thread(thread), _safepoint_safe(false),
929 _safepoint_id(SafepointSynchronize::InactiveSafepointCounter),
930 _orig_thread_state(_thread_uninitialized), _next(NULL) {
931 }
932
933 void ThreadSafepointState::create(JavaThread *thread) {
934 ThreadSafepointState *state = new ThreadSafepointState(thread);
935 thread->set_safepoint_state(state);
936 }
937
938 void ThreadSafepointState::destroy(JavaThread *thread) {
939 if (thread->safepoint_state()) {
940 delete(thread->safepoint_state());
941 thread->set_safepoint_state(NULL);
942 }
943 }
944
945 uint64_t ThreadSafepointState::get_safepoint_id() const {
946 return OrderAccess::load_acquire(&_safepoint_id);
947 }
948
949 void ThreadSafepointState::reset_safepoint_id() {
950 OrderAccess::release_store(&_safepoint_id, SafepointSynchronize::InactiveSafepointCounter);
951 }
952
953 void ThreadSafepointState::set_safepoint_id(uint64_t safepoint_id) {
954 OrderAccess::release_store(&_safepoint_id, safepoint_id);
955 }
956
957 void ThreadSafepointState::examine_state_of_thread(uint64_t safepoint_count) {
958 assert(is_running(), "better be running or just have hit safepoint poll");
959
960 JavaThreadState stable_state;
961 if (!SafepointSynchronize::try_stable_load_state(&stable_state, _thread, safepoint_count)) {
962 // We could not get stable state of the JavaThread.
963 // Consider it running and just return.
964 return;
965 }
966
967 // Save the state at the start of safepoint processing.
968 _orig_thread_state = stable_state;
969
970 // Check for a thread that is suspended. Note that thread resume tries
971 // to grab the Threads_lock which we own here, so a thread cannot be
972 // resumed during safepoint synchronization.
973
974 // We check to see if this thread is suspended without locking to
975 // avoid deadlocking with a third thread that is waiting for this
976 // thread to be suspended. The third thread can notice the safepoint
977 // that we're trying to start at the beginning of its SR_lock->wait()
978 // call. If that happens, then the third thread will block on the
979 // safepoint while still holding the underlying SR_lock. We won't be
980 // able to get the SR_lock and we'll deadlock.
981 //
982 // We don't need to grab the SR_lock here for two reasons:
983 // 1) The suspend flags are both volatile and are set with an
984 // Atomic::cmpxchg() call so we should see the suspended
985 // state right away.
986 // 2) We're being called from the safepoint polling loop; if
987 // we don't see the suspended state on this iteration, then
988 // we'll come around again.
989 //
990 bool is_suspended = _thread->is_ext_suspended();
991 if (is_suspended) {
992 account_safe_thread();
993 return;
994 }
995
996 if (safepoint_safe_with(_thread, stable_state)) {
997 check_for_lazy_critical_native(_thread, stable_state);
998 account_safe_thread();
999 return;
1000 }
1001
1002 // All other thread states will continue to run until they
1003 // transition and self-block in state _blocked
1004 // Safepoint polling in compiled code causes the Java threads to do the same.
1005 // Note: new threads may require a malloc so they must be allowed to finish
1006
1007 assert(is_running(), "examine_state_of_thread on non-running thread");
1008 return;
1009 }
1010
1011 void ThreadSafepointState::account_safe_thread() {
1012 SafepointSynchronize::decrement_waiting_to_block();
1013 if (_thread->in_critical()) {
1014 // Notice that this thread is in a critical section
1015 SafepointSynchronize::increment_jni_active_count();
1016 }
1017 DEBUG_ONLY(_thread->set_visited_for_critical_count(SafepointSynchronize::safepoint_counter());)
1018 assert(!_safepoint_safe, "Must be unsafe before safe");
1019 _safepoint_safe = true;
1020 }
1021
1022 void ThreadSafepointState::restart() {
1023 assert(_safepoint_safe, "Must be safe before unsafe");
1024 _safepoint_safe = false;
1025 }
1026
1027 void ThreadSafepointState::print_on(outputStream *st) const {
1028 const char *s = _safepoint_safe ? "_at_safepoint" : "_running";
1029
1030 st->print_cr("Thread: " INTPTR_FORMAT
1031 " [0x%2x] State: %s _at_poll_safepoint %d",
1032 p2i(_thread), _thread->osthread()->thread_id(), s, _at_poll_safepoint);
1033
1034 _thread->print_thread_state_on(st);
1035 }
1036
1037 // ---------------------------------------------------------------------------------------------------------------------
1038
1039 // Block the thread at poll or poll return for safepoint/handshake.
1040 void ThreadSafepointState::handle_polling_page_exception() {
1041
1042 // If we're using a global poll, then the thread should not be
1043 // marked as safepoint safe yet.
1044 assert(!SafepointMechanism::uses_global_page_poll() || !_safepoint_safe,
1045 "polling page exception on thread safepoint safe");
1046
1047 // Step 1: Find the nmethod from the return address
1048 address real_return_addr = thread()->saved_exception_pc();
1049
1050 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1051 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1052 CompiledMethod* nm = (CompiledMethod*)cb;
1053
1054 // Find frame of caller
1055 frame stub_fr = thread()->last_frame();
1056 CodeBlob* stub_cb = stub_fr.cb();
1057 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1058 RegisterMap map(thread(), true);
1059 frame caller_fr = stub_fr.sender(&map);
1060
1061 // Should only be poll_return or poll
1062 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1063
1064 // This is a poll immediately before a return. The exception handling code
1065 // has already had the effect of causing the return to occur, so the execution
1066 // will continue immediately after the call. In addition, the oopmap at the
1067 // return point does not mark the return value as an oop (if it is), so
1068 // it needs a handle here to be updated.
1069 if( nm->is_at_poll_return(real_return_addr) ) {
1070 // See if return type is an oop.
1071 bool return_oop = nm->method()->is_returning_oop();
1072 Handle return_value;
1073 if (return_oop) {
1074 // The oop result has been saved on the stack together with all
1075 // the other registers. In order to preserve it over GCs we need
1076 // to keep it in a handle.
1077 oop result = caller_fr.saved_oop_result(&map);
1078 assert(oopDesc::is_oop_or_null(result), "must be oop");
1079 return_value = Handle(thread(), result);
1080 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1081 }
1082
1083 // Block the thread
1084 SafepointMechanism::block_if_requested(thread());
1085
1086 // restore oop result, if any
1087 if (return_oop) {
1088 caller_fr.set_saved_oop_result(&map, return_value());
1089 }
1090 }
1091
1092 // This is a safepoint poll. Verify the return address and block.
1093 else {
1094 set_at_poll_safepoint(true);
1095
1096 // verify the blob built the "return address" correctly
1097 assert(real_return_addr == caller_fr.pc(), "must match");
1098
1099 // Block the thread
1100 SafepointMechanism::block_if_requested(thread());
1101 set_at_poll_safepoint(false);
1102
1103 // If we have a pending async exception deoptimize the frame
1104 // as otherwise we may never deliver it.
1105 if (thread()->has_async_condition()) {
1106 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1107 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1108 }
1109
1110 // If an exception has been installed we must check for a pending deoptimization
1111 // Deoptimize frame if exception has been thrown.
1112
1113 if (thread()->has_pending_exception() ) {
1114 RegisterMap map(thread(), true);
1115 frame caller_fr = stub_fr.sender(&map);
1116 if (caller_fr.is_deoptimized_frame()) {
1117 // The exception patch will destroy registers that are still
1118 // live and will be needed during deoptimization. Defer the
1119 // Async exception should have deferred the exception until the
1120 // next safepoint which will be detected when we get into
1121 // the interpreter so if we have an exception now things
1122 // are messed up.
1123
1124 fatal("Exception installed and deoptimization is pending");
1125 }
1126 }
1127 }
1128 }
1129
1130
1131 // -------------------------------------------------------------------------------------------------------
1132 // Implementation of SafepointTracing
1133
1134 jlong SafepointTracing::_last_safepoint_begin_time_ns = 0;
1135 jlong SafepointTracing::_last_safepoint_sync_time_ns = 0;
1136 jlong SafepointTracing::_last_safepoint_cleanup_time_ns = 0;
1137 jlong SafepointTracing::_last_safepoint_end_time_ns = 0;
1138 jlong SafepointTracing::_last_safepoint_end_time_epoch_ms = 0;
1139 jlong SafepointTracing::_last_app_time_ns = 0;
1140 int SafepointTracing::_nof_threads = 0;
1141 int SafepointTracing::_nof_running = 0;
1142 int SafepointTracing::_page_trap = 0;
1143 VM_Operation::VMOp_Type SafepointTracing::_current_type;
1144 jlong SafepointTracing::_max_sync_time = 0;
1145 jlong SafepointTracing::_max_vmop_time = 0;
1146 uint64_t SafepointTracing::_op_count[VM_Operation::VMOp_Terminating] = {0};
1147
1148 void SafepointTracing::init() {
1149 // Application start
1150 _last_safepoint_end_time_ns = os::javaTimeNanos();
1151 // amount of time since epoch
1152 _last_safepoint_end_time_epoch_ms = os::javaTimeMillis();
1153 }
1154
1155 // Helper method to print the header.
1156 static void print_header(outputStream* st) {
1157 // The number of spaces is significant here, and should match the format
1158 // specifiers in print_statistics().
1159
1160 st->print("VM Operation "
1161 "[ threads: total initial_running ]"
1162 "[ time: sync cleanup vmop total ]");
1163
1164 st->print_cr(" page_trap_count");
1165 }
1166
1167 // This prints a nice table. To get the statistics to not shift due to the logging uptime
1168 // decorator, use the option as: -Xlog:safepoint+stats:[outputfile]:none
1169 void SafepointTracing::statistics_log() {
1170 LogTarget(Info, safepoint, stats) lt;
1171 assert (lt.is_enabled(), "should only be called when printing statistics is enabled");
1172 LogStream ls(lt);
1173
1174 static int _cur_stat_index = 0;
1175
1176 // Print header every 30 entries
1177 if ((_cur_stat_index % 30) == 0) {
1178 print_header(&ls);
1179 _cur_stat_index = 1; // wrap
1180 } else {
1181 _cur_stat_index++;
1182 }
1183
1184 ls.print("%-28s [ "
1185 INT32_FORMAT_W(8) " " INT32_FORMAT_W(8) " "
1186 "]",
1187 VM_Operation::name(_current_type),
1188 _nof_threads,
1189 _nof_running);
1190 ls.print("[ "
1191 INT64_FORMAT_W(10) " " INT64_FORMAT_W(10) " "
1192 INT64_FORMAT_W(10) " " INT64_FORMAT_W(10) " ]",
1193 (int64_t)(_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns),
1194 (int64_t)(_last_safepoint_cleanup_time_ns - _last_safepoint_sync_time_ns),
1195 (int64_t)(_last_safepoint_end_time_ns - _last_safepoint_cleanup_time_ns),
1196 (int64_t)(_last_safepoint_end_time_ns - _last_safepoint_begin_time_ns));
1197
1198 ls.print_cr(INT32_FORMAT_W(16), _page_trap);
1199 }
1200
1201 // This method will be called when VM exits. This tries to summarize the sampling.
1202 // Current thread may already be deleted, so don't use ResourceMark.
1203 void SafepointTracing::statistics_exit_log() {
1204 if (!log_is_enabled(Info, safepoint, stats)) {
1205 return;
1206 }
1207 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1208 if (_op_count[index] != 0) {
1209 log_info(safepoint, stats)("%-28s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1210 _op_count[index]);
1211 }
1212 }
1213
1214 log_info(safepoint, stats)("VM operations coalesced during safepoint " INT64_FORMAT,
1215 VMThread::get_coalesced_count());
1216 log_info(safepoint, stats)("Maximum sync time " INT64_FORMAT" ns",
1217 (int64_t)(_max_sync_time));
1218 log_info(safepoint, stats)("Maximum vm operation time (except for Exit VM operation) "
1219 INT64_FORMAT " ns",
1220 (int64_t)(_max_vmop_time));
1221 }
1222
1223 void SafepointTracing::begin(VM_Operation::VMOp_Type type) {
1224 _op_count[type]++;
1225 _current_type = type;
1226
1227 // update the time stamp to begin recording safepoint time
1228 _last_safepoint_begin_time_ns = os::javaTimeNanos();
1229 _last_safepoint_sync_time_ns = 0;
1230 _last_safepoint_cleanup_time_ns = 0;
1231
1232 _last_app_time_ns = _last_safepoint_begin_time_ns - _last_safepoint_end_time_ns;
1233 _last_safepoint_end_time_ns = 0;
1234
1235 RuntimeService::record_safepoint_begin(_last_app_time_ns);
1236 }
1237
1238 void SafepointTracing::synchronized(int nof_threads, int nof_running, int traps) {
1239 _last_safepoint_sync_time_ns = os::javaTimeNanos();
1240 _nof_threads = nof_threads;
1241 _nof_running = nof_running;
1242 _page_trap = traps;
1243 RuntimeService::record_safepoint_synchronized(_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns);
1244 }
1245
1246 void SafepointTracing::cleanup() {
1247 _last_safepoint_cleanup_time_ns = os::javaTimeNanos();
1248 }
1249
1250 void SafepointTracing::end() {
1251 _last_safepoint_end_time_ns = os::javaTimeNanos();
1252 // amount of time since epoch
1253 _last_safepoint_end_time_epoch_ms = os::javaTimeMillis();
1254
1255 if (_max_sync_time < (_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns)) {
1256 _max_sync_time = _last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns;
1257 }
1258 if (_max_vmop_time < (_last_safepoint_end_time_ns - _last_safepoint_sync_time_ns)) {
1259 _max_vmop_time = _last_safepoint_end_time_ns - _last_safepoint_sync_time_ns;
1260 }
1261 if (log_is_enabled(Info, safepoint, stats)) {
1262 statistics_log();
1263 }
1264
1265 log_info(safepoint)(
1266 "Safepoint \"%s\", "
1267 "Time since last: " JLONG_FORMAT " ns, "
1268 "Reaching safepoint: " JLONG_FORMAT " ns, "
1269 "At safepoint: " JLONG_FORMAT " ns, "
1270 "Total: " JLONG_FORMAT " ns",
1271 VM_Operation::name(_current_type),
1272 _last_app_time_ns,
1273 _last_safepoint_cleanup_time_ns - _last_safepoint_begin_time_ns,
1274 _last_safepoint_end_time_ns - _last_safepoint_cleanup_time_ns,
1275 _last_safepoint_end_time_ns - _last_safepoint_begin_time_ns
1276 );
1277
1278 RuntimeService::record_safepoint_end(_last_safepoint_end_time_ns - _last_safepoint_cleanup_time_ns);
1279 }