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/dictionary.hpp"
28 #include "classfile/stringTable.hpp"
29 #include "classfile/symbolTable.hpp"
30 #include "classfile/systemDictionary.hpp"
31 #include "code/codeCache.hpp"
32 #include "code/icBuffer.hpp"
33 #include "code/nmethod.hpp"
34 #include "code/pcDesc.hpp"
35 #include "code/scopeDesc.hpp"
36 #include "gc/shared/collectedHeap.hpp"
37 #include "gc/shared/gcLocker.hpp"
38 #include "gc/shared/oopStorage.hpp"
39 #include "gc/shared/strongRootsScope.hpp"
40 #include "gc/shared/workgroup.hpp"
41 #include "interpreter/interpreter.hpp"
42 #include "jfr/jfrEvents.hpp"
43 #include "logging/log.hpp"
44 #include "logging/logStream.hpp"
45 #include "memory/resourceArea.hpp"
46 #include "memory/universe.hpp"
47 #include "oops/oop.inline.hpp"
48 #include "oops/symbol.hpp"
49 #include "runtime/atomic.hpp"
50 #include "runtime/compilationPolicy.hpp"
51 #include "runtime/deoptimization.hpp"
52 #include "runtime/frame.inline.hpp"
53 #include "runtime/handles.inline.hpp"
54 #include "runtime/interfaceSupport.inline.hpp"
55 #include "runtime/mutexLocker.hpp"
56 #include "runtime/orderAccess.hpp"
57 #include "runtime/osThread.hpp"
58 #include "runtime/safepoint.hpp"
59 #include "runtime/safepointMechanism.inline.hpp"
60 #include "runtime/signature.hpp"
61 #include "runtime/stubCodeGenerator.hpp"
62 #include "runtime/stubRoutines.hpp"
63 #include "runtime/sweeper.hpp"
64 #include "runtime/synchronizer.hpp"
65 #include "runtime/thread.inline.hpp"
66 #include "runtime/threadSMR.hpp"
67 #include "runtime/timerTrace.hpp"
68 #include "services/runtimeService.hpp"
69 #include "utilities/events.hpp"
70 #include "utilities/macros.hpp"
71
72 static void post_safepoint_begin_event(EventSafepointBegin& event,
73 uint64_t safepoint_id,
74 int thread_count,
75 int critical_thread_count) {
76 if (event.should_commit()) {
77 event.set_safepointId(safepoint_id);
78 event.set_totalThreadCount(thread_count);
79 event.set_jniCriticalThreadCount(critical_thread_count);
80 event.commit();
81 }
82 }
83
84 static void post_safepoint_cleanup_event(EventSafepointCleanup& event, uint64_t safepoint_id) {
85 if (event.should_commit()) {
86 event.set_safepointId(safepoint_id);
87 event.commit();
88 }
89 }
90
91 static void post_safepoint_synchronize_event(EventSafepointStateSynchronization& event,
92 uint64_t safepoint_id,
93 int initial_number_of_threads,
94 int threads_waiting_to_block,
95 uint64_t iterations) {
96 if (event.should_commit()) {
97 event.set_safepointId(safepoint_id);
98 event.set_initialThreadCount(initial_number_of_threads);
99 event.set_runningThreadCount(threads_waiting_to_block);
100 event.set_iterations(iterations);
101 event.commit();
102 }
103 }
104
105 static void post_safepoint_cleanup_task_event(EventSafepointCleanupTask& event,
106 uint64_t safepoint_id,
107 const char* name) {
108 if (event.should_commit()) {
109 event.set_safepointId(safepoint_id);
110 event.set_name(name);
111 event.commit();
112 }
113 }
114
115 static void post_safepoint_end_event(EventSafepointEnd& event, uint64_t safepoint_id) {
116 if (event.should_commit()) {
117 event.set_safepointId(safepoint_id);
118 event.commit();
119 }
120 }
121
122 // SafepointCheck
123 SafepointStateTracker::SafepointStateTracker(uint64_t safepoint_id, bool at_safepoint)
124 : _safepoint_id(safepoint_id), _at_safepoint(at_safepoint) {}
125
126 bool SafepointStateTracker::safepoint_state_changed() {
127 return _safepoint_id != SafepointSynchronize::safepoint_id() ||
128 _at_safepoint != SafepointSynchronize::is_at_safepoint();
129 }
130
131 // --------------------------------------------------------------------------------------------------
132 // Implementation of Safepoint begin/end
133
134 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
135 int SafepointSynchronize::_waiting_to_block = 0;
136 volatile uint64_t SafepointSynchronize::_safepoint_counter = 0;
137 uint64_t SafepointSynchronize::_safepoint_id = 0;
138 const uint64_t SafepointSynchronize::InactiveSafepointCounter = 0;
139 int SafepointSynchronize::_current_jni_active_count = 0;
140
141 WaitBarrier* SafepointSynchronize::_wait_barrier;
142
143 static volatile bool PageArmed = false; // safepoint polling page is RO|RW vs PROT_NONE
144 static bool timeout_error_printed = false;
145
146 // Statistic related
147 static jlong _safepoint_begin_time = 0;
148 static volatile int _nof_threads_hit_polling_page = 0;
149
150 void SafepointSynchronize::init(Thread* vmthread) {
151 // WaitBarrier should never be destroyed since we will have
152 // threads waiting on it while exiting.
153 _wait_barrier = new WaitBarrier(vmthread);
154 SafepointTracing::init();
155 }
156
157 void SafepointSynchronize::increment_jni_active_count() {
158 assert(Thread::current()->is_VM_thread(), "Only VM thread may increment");
159 ++_current_jni_active_count;
160 }
161
162 void SafepointSynchronize::decrement_waiting_to_block() {
163 assert(_waiting_to_block > 0, "sanity check");
164 assert(Thread::current()->is_VM_thread(), "Only VM thread may decrement");
165 --_waiting_to_block;
166 }
167
168 bool SafepointSynchronize::thread_not_running(ThreadSafepointState *cur_state) {
169 if (!cur_state->is_running()) {
170 return true;
171 }
172 cur_state->examine_state_of_thread(SafepointSynchronize::safepoint_counter());
173 if (!cur_state->is_running()) {
174 return true;
175 }
176 LogTarget(Trace, safepoint) lt;
177 if (lt.is_enabled()) {
178 ResourceMark rm;
179 LogStream ls(lt);
180 cur_state->print_on(&ls);
181 }
182 return false;
183 }
184
185 #ifdef ASSERT
186 static void assert_list_is_valid(const ThreadSafepointState* tss_head, int still_running) {
187 int a = 0;
188 const ThreadSafepointState *tmp_tss = tss_head;
189 while (tmp_tss != NULL) {
190 ++a;
191 assert(tmp_tss->is_running(), "Illegal initial state");
192 tmp_tss = tmp_tss->get_next();
193 }
194 assert(a == still_running, "Must be the same");
195 }
196 #endif // ASSERT
197
198 static void back_off(int64_t start_time) {
199 // We start with fine-grained nanosleeping until a millisecond has
200 // passed, at which point we resort to plain naked_short_sleep.
201 if (os::javaTimeNanos() - start_time < NANOSECS_PER_MILLISEC) {
202 os::naked_short_nanosleep(10 * (NANOUNITS / MICROUNITS));
203 } else {
204 os::naked_short_sleep(1);
205 }
206 }
207
208 int SafepointSynchronize::synchronize_threads(jlong safepoint_limit_time, int nof_threads, int* initial_running)
209 {
210 JavaThreadIteratorWithHandle jtiwh;
211
212 #ifdef ASSERT
213 for (; JavaThread *cur = jtiwh.next(); ) {
214 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
215 }
216 jtiwh.rewind();
217 #endif // ASSERT
218
219 // Iterate through all threads until it has been determined how to stop them all at a safepoint.
220 int still_running = nof_threads;
221 ThreadSafepointState *tss_head = NULL;
222 ThreadSafepointState **p_prev = &tss_head;
223 for (; JavaThread *cur = jtiwh.next(); ) {
224 ThreadSafepointState *cur_tss = cur->safepoint_state();
225 assert(cur_tss->get_next() == NULL, "Must be NULL");
226 if (thread_not_running(cur_tss)) {
227 --still_running;
228 } else {
229 *p_prev = cur_tss;
230 p_prev = cur_tss->next_ptr();
231 }
232 }
233 *p_prev = NULL;
234
235 DEBUG_ONLY(assert_list_is_valid(tss_head, still_running);)
236
237 *initial_running = still_running;
238
239 // If there is no thread still running, we are already done.
240 if (still_running <= 0) {
241 assert(tss_head == NULL, "Must be empty");
242 return 1;
243 }
244
245 int iterations = 1; // The first iteration is above.
246 int64_t start_time = os::javaTimeNanos();
247
248 do {
249 // Check if this has taken too long:
250 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
251 print_safepoint_timeout();
252 }
253 if (int(iterations) == -1) { // overflow - something is wrong.
254 // We can only overflow here when we are using global
255 // polling pages. We keep this guarantee in its original
256 // form so that searches of the bug database for this
257 // failure mode find the right bugs.
258 guarantee (!PageArmed, "invariant");
259 }
260
261 p_prev = &tss_head;
262 ThreadSafepointState *cur_tss = tss_head;
263 while (cur_tss != NULL) {
264 assert(cur_tss->is_running(), "Illegal initial state");
265 if (thread_not_running(cur_tss)) {
266 --still_running;
267 *p_prev = NULL;
268 ThreadSafepointState *tmp = cur_tss;
269 cur_tss = cur_tss->get_next();
270 tmp->set_next(NULL);
271 } else {
272 *p_prev = cur_tss;
273 p_prev = cur_tss->next_ptr();
274 cur_tss = cur_tss->get_next();
275 }
276 }
277
278 DEBUG_ONLY(assert_list_is_valid(tss_head, still_running);)
279
280 if (still_running > 0) {
281 back_off(start_time);
282 }
283
284 iterations++;
285 } while (still_running > 0);
286
287 assert(tss_head == NULL, "Must be empty");
288
289 return iterations;
290 }
291
292 void SafepointSynchronize::arm_safepoint() {
293 // Begin the process of bringing the system to a safepoint.
294 // Java threads can be in several different states and are
295 // stopped by different mechanisms:
296 //
297 // 1. Running interpreted
298 // When executing branching/returning byte codes interpreter
299 // checks if the poll is armed, if so blocks in SS::block().
300 // When using global polling the interpreter dispatch table
301 // is changed to force it to check for a safepoint condition
302 // between bytecodes.
303 // 2. Running in native code
304 // When returning from the native code, a Java thread must check
305 // the safepoint _state to see if we must block. If the
306 // VM thread sees a Java thread in native, it does
307 // not wait for this thread to block. The order of the memory
308 // writes and reads of both the safepoint state and the Java
309 // threads state is critical. In order to guarantee that the
310 // memory writes are serialized with respect to each other,
311 // the VM thread issues a memory barrier instruction.
312 // 3. Running compiled Code
313 // Compiled code reads the local polling page that
314 // is set to fault if we are trying to get to a safepoint.
315 // 4. Blocked
316 // A thread which is blocked will not be allowed to return from the
317 // block condition until the safepoint operation is complete.
318 // 5. In VM or Transitioning between states
319 // If a Java thread is currently running in the VM or transitioning
320 // between states, the safepointing code will poll the thread state
321 // until the thread blocks itself when it attempts transitions to a
322 // new state or locking a safepoint checked monitor.
323
324 // We must never miss a thread with correct safepoint id, so we must make sure we arm
325 // the wait barrier for the next safepoint id/counter.
326 // Arming must be done after resetting _current_jni_active_count, _waiting_to_block.
327 _wait_barrier->arm(static_cast<int>(_safepoint_counter + 1));
328
329 assert((_safepoint_counter & 0x1) == 0, "must be even");
330 // The store to _safepoint_counter must happen after any stores in arming.
331 OrderAccess::release_store(&_safepoint_counter, _safepoint_counter + 1);
332
333 // We are synchronizing
334 OrderAccess::storestore(); // Ordered with _safepoint_counter
335 _state = _synchronizing;
336
337 if (SafepointMechanism::uses_thread_local_poll()) {
338 // Arming the per thread poll while having _state != _not_synchronized means safepointing
339 log_trace(safepoint)("Setting thread local yield flag for threads");
340 OrderAccess::storestore(); // storestore, global state -> local state
341 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
342 // Make sure the threads start polling, it is time to yield.
343 SafepointMechanism::arm_local_poll(cur);
344 }
345 }
346 OrderAccess::fence(); // storestore|storeload, global state -> local state
347
348 if (SafepointMechanism::uses_global_page_poll()) {
349 // Make interpreter safepoint aware
350 Interpreter::notice_safepoints();
351
352 // Make polling safepoint aware
353 guarantee (!PageArmed, "invariant") ;
354 PageArmed = true;
355 os::make_polling_page_unreadable();
356 }
357 }
358
359 // Roll all threads forward to a safepoint and suspend them all
360 void SafepointSynchronize::begin() {
361 assert(Thread::current()->is_VM_thread(), "Only VM thread may execute a safepoint");
362
363 EventSafepointBegin begin_event;
364 SafepointTracing::begin(VMThread::vm_op_type());
365
366 Universe::heap()->safepoint_synchronize_begin();
367
368 // By getting the Threads_lock, we assure that no threads are about to start or
369 // exit. It is released again in SafepointSynchronize::end().
370 Threads_lock->lock();
371
372 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
373
374 int nof_threads = Threads::number_of_threads();
375
376 _nof_threads_hit_polling_page = 0;
377
378 log_debug(safepoint)("Safepoint synchronization initiated using %s wait barrier. (%d threads)", _wait_barrier->description(), nof_threads);
379
380 // Reset the count of active JNI critical threads
381 _current_jni_active_count = 0;
382
383 // Set number of threads to wait for
384 _waiting_to_block = nof_threads;
385
386 jlong safepoint_limit_time = 0;
387 if (SafepointTimeout) {
388 // Set the limit time, so that it can be compared to see if this has taken
389 // too long to complete.
390 safepoint_limit_time = SafepointTracing::start_of_safepoint() + (jlong)SafepointTimeoutDelay * (NANOUNITS / MILLIUNITS);
391 timeout_error_printed = false;
392 }
393
394 EventSafepointStateSynchronization sync_event;
395 int initial_running = 0;
396
397 // Arms the safepoint, _current_jni_active_count and _waiting_to_block must be set before.
398 arm_safepoint();
399
400 // Will spin until all threads are safe.
401 int iterations = synchronize_threads(safepoint_limit_time, nof_threads, &initial_running);
402 assert(_waiting_to_block == 0, "No thread should be running");
403
404 #ifndef PRODUCT
405 if (safepoint_limit_time != 0) {
406 jlong current_time = os::javaTimeNanos();
407 if (safepoint_limit_time < current_time) {
408 log_warning(safepoint)("# SafepointSynchronize: Finished after "
409 INT64_FORMAT_W(6) " ms",
410 (int64_t)(current_time - SafepointTracing::start_of_safepoint()) / (NANOUNITS / MILLIUNITS));
411 }
412 }
413 #endif
414
415 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
416
417 // Record state
418 _state = _synchronized;
419
420 OrderAccess::fence();
421
422 // Set the new id
423 ++_safepoint_id;
424
425 #ifdef ASSERT
426 // Make sure all the threads were visited.
427 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
428 assert(cur->was_visited_for_critical_count(_safepoint_counter), "missed a thread");
429 }
430 #endif // ASSERT
431
432 // Update the count of active JNI critical regions
433 GCLocker::set_jni_lock_count(_current_jni_active_count);
434
435 post_safepoint_synchronize_event(sync_event,
436 _safepoint_id,
437 initial_running,
438 _waiting_to_block, iterations);
439
440 SafepointTracing::synchronized(nof_threads, initial_running, _nof_threads_hit_polling_page);
441
442 // We do the safepoint cleanup first since a GC related safepoint
443 // needs cleanup to be completed before running the GC op.
444 EventSafepointCleanup cleanup_event;
445 do_cleanup_tasks();
446 post_safepoint_cleanup_event(cleanup_event, _safepoint_id);
447
448 post_safepoint_begin_event(begin_event, _safepoint_id, nof_threads, _current_jni_active_count);
449 SafepointTracing::cleanup();
450 }
451
452 void SafepointSynchronize::disarm_safepoint() {
453 uint64_t active_safepoint_counter = _safepoint_counter;
454 {
455 JavaThreadIteratorWithHandle jtiwh;
456 #ifdef ASSERT
457 // A pending_exception cannot be installed during a safepoint. The threads
458 // may install an async exception after they come back from a safepoint into
459 // pending_exception after they unblock. But that should happen later.
460 for (; JavaThread *cur = jtiwh.next(); ) {
461 assert (!(cur->has_pending_exception() &&
462 cur->safepoint_state()->is_at_poll_safepoint()),
463 "safepoint installed a pending exception");
464 }
465 #endif // ASSERT
466
467 if (SafepointMechanism::uses_global_page_poll()) {
468 guarantee (PageArmed, "invariant");
469 // Make polling safepoint aware
470 os::make_polling_page_readable();
471 PageArmed = false;
472 // Remove safepoint check from interpreter
473 Interpreter::ignore_safepoints();
474 }
475
476 OrderAccess::fence(); // keep read and write of _state from floating up
477 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
478
479 // Change state first to _not_synchronized.
480 // No threads should see _synchronized when running.
481 _state = _not_synchronized;
482
483 // Set the next dormant (even) safepoint id.
484 assert((_safepoint_counter & 0x1) == 1, "must be odd");
485 OrderAccess::release_store(&_safepoint_counter, _safepoint_counter + 1);
486
487 OrderAccess::fence(); // Keep the local state from floating up.
488
489 jtiwh.rewind();
490 for (; JavaThread *current = jtiwh.next(); ) {
491 // Clear the visited flag to ensure that the critical counts are collected properly.
492 DEBUG_ONLY(current->reset_visited_for_critical_count(active_safepoint_counter);)
493 ThreadSafepointState* cur_state = current->safepoint_state();
494 assert(!cur_state->is_running(), "Thread not suspended at safepoint");
495 cur_state->restart(); // TSS _running
496 assert(cur_state->is_running(), "safepoint state has not been reset");
497
498 SafepointMechanism::disarm_if_needed(current, false /* NO release */);
499 }
500 } // ~JavaThreadIteratorWithHandle
501
502 // Release threads lock, so threads can be created/destroyed again.
503 Threads_lock->unlock();
504
505 // Wake threads after local state is correctly set.
506 _wait_barrier->disarm();
507 }
508
509 // Wake up all threads, so they are ready to resume execution after the safepoint
510 // operation has been carried out
511 void SafepointSynchronize::end() {
512 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
513 EventSafepointEnd event;
514 assert(Thread::current()->is_VM_thread(), "Only VM thread can execute a safepoint");
515
516 disarm_safepoint();
517
518 Universe::heap()->safepoint_synchronize_end();
519
520 SafepointTracing::end();
521
522 post_safepoint_end_event(event, safepoint_id());
523 }
524
525 bool SafepointSynchronize::is_cleanup_needed() {
526 // Need a cleanup safepoint if there are too many monitors in use
527 // and the monitor deflation needs to be done at a safepoint.
528 if (ObjectSynchronizer::is_safepoint_deflation_needed()) return true;
529 // Need a safepoint if some inline cache buffers is non-empty
530 if (!InlineCacheBuffer::is_empty()) return true;
531 if (StringTable::needs_rehashing()) return true;
532 if (SymbolTable::needs_rehashing()) return true;
533 return false;
534 }
535
536 class ParallelSPCleanupThreadClosure : public ThreadClosure {
537 private:
538 CodeBlobClosure* _nmethod_cl;
539 DeflateMonitorCounters* _counters;
540
541 public:
542 ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) :
543 _nmethod_cl(UseCodeAging ? NMethodSweeper::prepare_reset_hotness_counters() : NULL),
544 _counters(counters) {}
545
546 void do_thread(Thread* thread) {
547 // deflate_thread_local_monitors() handles or requests deflation of
548 // this thread's idle monitors. If !AsyncDeflateIdleMonitors or if
549 // there is a special cleanup request, deflation is handled now.
550 // Otherwise, async deflation is requested via a flag.
551 ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters);
552 if (_nmethod_cl != NULL && thread->is_Java_thread() &&
553 ! thread->is_Code_cache_sweeper_thread()) {
554 JavaThread* jt = (JavaThread*) thread;
555 jt->nmethods_do(_nmethod_cl);
556 }
557 }
558 };
559
560 class ParallelSPCleanupTask : public AbstractGangTask {
561 private:
562 SubTasksDone _subtasks;
563 ParallelSPCleanupThreadClosure _cleanup_threads_cl;
564 uint _num_workers;
565 DeflateMonitorCounters* _counters;
566 public:
567 ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
568 AbstractGangTask("Parallel Safepoint Cleanup"),
569 _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)),
570 _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
571 _num_workers(num_workers),
572 _counters(counters) {}
573
574 void work(uint worker_id) {
575 uint64_t safepoint_id = SafepointSynchronize::safepoint_id();
576 // All threads deflate monitors and mark nmethods (if necessary).
577 Threads::possibly_parallel_threads_do(true, &_cleanup_threads_cl);
578
579 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
580 const char* name = "deflating global idle monitors";
581 EventSafepointCleanupTask event;
582 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
583 // AsyncDeflateIdleMonitors only uses DeflateMonitorCounters
584 // when a special cleanup has been requested.
585 // Note: This logging output will include global idle monitor
586 // elapsed times, but not global idle monitor deflation count.
587 ObjectSynchronizer::do_safepoint_work(_counters);
588
589 post_safepoint_cleanup_task_event(event, safepoint_id, name);
590 }
591
592 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
593 const char* name = "updating inline caches";
594 EventSafepointCleanupTask event;
595 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
596 InlineCacheBuffer::update_inline_caches();
597
598 post_safepoint_cleanup_task_event(event, safepoint_id, name);
599 }
600
601 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
602 const char* name = "compilation policy safepoint handler";
603 EventSafepointCleanupTask event;
604 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
605 CompilationPolicy::policy()->do_safepoint_work();
606
607 post_safepoint_cleanup_task_event(event, safepoint_id, name);
608 }
609
610 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
611 if (SymbolTable::needs_rehashing()) {
612 const char* name = "rehashing symbol table";
613 EventSafepointCleanupTask event;
614 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
615 SymbolTable::rehash_table();
616
617 post_safepoint_cleanup_task_event(event, safepoint_id, name);
618 }
619 }
620
621 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
622 if (StringTable::needs_rehashing()) {
623 const char* name = "rehashing string table";
624 EventSafepointCleanupTask event;
625 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
626 StringTable::rehash_table();
627
628 post_safepoint_cleanup_task_event(event, safepoint_id, name);
629 }
630 }
631
632 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) {
633 if (ClassLoaderDataGraph::should_purge_and_reset()) {
634 // CMS delays purging the CLDG until the beginning of the next safepoint and to
635 // make sure concurrent sweep is done
636 const char* name = "purging class loader data graph";
637 EventSafepointCleanupTask event;
638 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
639 ClassLoaderDataGraph::purge();
640
641 post_safepoint_cleanup_task_event(event, safepoint_id, name);
642 }
643 }
644
645 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_SYSTEM_DICTIONARY_RESIZE)) {
646 if (Dictionary::does_any_dictionary_needs_resizing()) {
647 const char* name = "resizing system dictionaries";
648 EventSafepointCleanupTask event;
649 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
650 ClassLoaderDataGraph::resize_dictionaries();
651
652 post_safepoint_cleanup_task_event(event, safepoint_id, name);
653 }
654 }
655
656 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_REQUEST_OOPSTORAGE_CLEANUP)) {
657 // Don't bother reporting event or time for this very short operation.
658 // To have any utility we'd also want to report whether needed.
659 OopStorage::trigger_cleanup_if_needed();
660 }
661
662 _subtasks.all_tasks_completed(_num_workers);
663 }
664 };
665
666 // Various cleaning tasks that should be done periodically at safepoints.
667 void SafepointSynchronize::do_cleanup_tasks() {
668
669 TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup));
670
671 // Prepare for monitor deflation.
672 DeflateMonitorCounters deflate_counters;
673 ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
674
675 CollectedHeap* heap = Universe::heap();
676 assert(heap != NULL, "heap not initialized yet?");
677 WorkGang* cleanup_workers = heap->get_safepoint_workers();
678 if (cleanup_workers != NULL) {
679 // Parallel cleanup using GC provided thread pool.
680 uint num_cleanup_workers = cleanup_workers->active_workers();
681 ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
682 StrongRootsScope srs(num_cleanup_workers);
683 cleanup_workers->run_task(&cleanup);
684 } else {
685 // Serial cleanup using VMThread.
686 ParallelSPCleanupTask cleanup(1, &deflate_counters);
687 StrongRootsScope srs(1);
688 cleanup.work(0);
689 }
690
691 // Needs to be done single threaded by the VMThread. This walks
692 // the thread stacks looking for references to metadata before
693 // deciding to remove it from the metaspaces.
694 if (ClassLoaderDataGraph::should_clean_metaspaces_and_reset()) {
695 const char* name = "cleanup live ClassLoaderData metaspaces";
696 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
697 ClassLoaderDataGraph::walk_metadata_and_clean_metaspaces();
698 }
699
700 // Finish monitor deflation.
701 ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
702
703 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
704 }
705
706 // Methods for determining if a JavaThread is safepoint safe.
707
708 // False means unsafe with undetermined state.
709 // True means a determined state, but it may be an unsafe state.
710 // If called from a non-safepoint context safepoint_count MUST be InactiveSafepointCounter.
711 bool SafepointSynchronize::try_stable_load_state(JavaThreadState *state, JavaThread *thread, uint64_t safepoint_count) {
712 assert((safepoint_count != InactiveSafepointCounter &&
713 Thread::current() == (Thread*)VMThread::vm_thread() &&
714 SafepointSynchronize::_state != _not_synchronized)
715 || safepoint_count == InactiveSafepointCounter, "Invalid check");
716
717 // To handle the thread_blocked state on the backedge of the WaitBarrier from
718 // previous safepoint and reading the reset value (0/InactiveSafepointCounter) we
719 // re-read state after we read thread safepoint id. The JavaThread changes its
720 // thread state from thread_blocked before resetting safepoint id to 0.
721 // This guarantees the second read will be from an updated thread state. It can
722 // either be different state making this an unsafe state or it can see blocked
723 // again. When we see blocked twice with a 0 safepoint id, either:
724 // - It is normally blocked, e.g. on Mutex, TBIVM.
725 // - It was in SS:block(), looped around to SS:block() and is blocked on the WaitBarrier.
726 // - It was in SS:block() but now on a Mutex.
727 // All of these cases are safe.
728
729 *state = thread->thread_state();
730 OrderAccess::loadload();
731 uint64_t sid = thread->safepoint_state()->get_safepoint_id(); // Load acquire
732 if (sid != InactiveSafepointCounter && sid != safepoint_count) {
733 // In an old safepoint, state not relevant.
734 return false;
735 }
736 return *state == thread->thread_state();
737 }
738
739 static bool safepoint_safe_with(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 case _thread_blocked:
746 // On wait_barrier or blocked.
747 // Blocked threads should already have walkable stack.
748 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
749 return true;
750
751 default:
752 return false;
753 }
754 }
755
756 bool SafepointSynchronize::handshake_safe(JavaThread *thread) {
757 // This function must be called with the Threads_lock held so an externally
758 // suspended thread cannot be resumed thus it is safe.
759 assert(Threads_lock->owned_by_self() && Thread::current()->is_VM_thread(),
760 "Must hold Threads_lock and be VMThread");
761 if (thread->is_ext_suspended() || thread->is_terminated()) {
762 return true;
763 }
764 JavaThreadState stable_state;
765 if (try_stable_load_state(&stable_state, thread, InactiveSafepointCounter)) {
766 return safepoint_safe_with(thread, stable_state);
767 }
768 return false;
769 }
770
771 // See if the thread is running inside a lazy critical native and
772 // update the thread critical count if so. Also set a suspend flag to
773 // cause the native wrapper to return into the JVM to do the unlock
774 // once the native finishes.
775 static void check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
776 if (state == _thread_in_native &&
777 thread->has_last_Java_frame() &&
778 thread->frame_anchor()->walkable()) {
779 // This thread might be in a critical native nmethod so look at
780 // the top of the stack and increment the critical count if it
781 // is.
782 frame wrapper_frame = thread->last_frame();
783 CodeBlob* stub_cb = wrapper_frame.cb();
784 if (stub_cb != NULL &&
785 stub_cb->is_nmethod() &&
786 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
787 // A thread could potentially be in a critical native across
788 // more than one safepoint, so only update the critical state on
789 // the first one. When it returns it will perform the unlock.
790 if (!thread->do_critical_native_unlock()) {
791 #ifdef ASSERT
792 if (!thread->in_critical()) {
793 GCLocker::increment_debug_jni_lock_count();
794 }
795 #endif
796 thread->enter_critical();
797 // Make sure the native wrapper calls back on return to
798 // perform the needed critical unlock.
799 thread->set_critical_native_unlock();
800 }
801 }
802 }
803 }
804
805 // -------------------------------------------------------------------------------------------------------
806 // Implementation of Safepoint blocking point
807
808 void SafepointSynchronize::block(JavaThread *thread) {
809 assert(thread != NULL, "thread must be set");
810 assert(thread->is_Java_thread(), "not a Java thread");
811
812 // Threads shouldn't block if they are in the middle of printing, but...
813 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
814
815 // Only bail from the block() call if the thread is gone from the
816 // thread list; starting to exit should still block.
817 if (thread->is_terminated()) {
818 // block current thread if we come here from native code when VM is gone
819 thread->block_if_vm_exited();
820
821 // otherwise do nothing
822 return;
823 }
824
825 JavaThreadState state = thread->thread_state();
826 thread->frame_anchor()->make_walkable(thread);
827
828 uint64_t safepoint_id = SafepointSynchronize::safepoint_counter();
829 // Check that we have a valid thread_state at this point
830 switch(state) {
831 case _thread_in_vm_trans:
832 case _thread_in_Java: // From compiled code
833 case _thread_in_native_trans:
834 case _thread_blocked_trans:
835 case _thread_new_trans:
836
837 // We have no idea where the VMThread is, it might even be at next safepoint.
838 // So we can miss this poll, but stop at next.
839
840 // Load dependent store, it must not pass loading of safepoint_id.
841 thread->safepoint_state()->set_safepoint_id(safepoint_id); // Release store
842
843 // This part we can skip if we notice we miss or are in a future safepoint.
844 OrderAccess::storestore();
845 // Load in wait barrier should not float up
846 thread->set_thread_state_fence(_thread_blocked);
847
848 _wait_barrier->wait(static_cast<int>(safepoint_id));
849 assert(_state != _synchronized, "Can't be");
850
851 // If barrier is disarmed stop store from floating above loads in barrier.
852 OrderAccess::loadstore();
853 thread->set_thread_state(state);
854
855 // Then we reset the safepoint id to inactive.
856 thread->safepoint_state()->reset_safepoint_id(); // Release store
857
858 OrderAccess::fence();
859
860 break;
861
862 default:
863 fatal("Illegal threadstate encountered: %d", state);
864 }
865 guarantee(thread->safepoint_state()->get_safepoint_id() == InactiveSafepointCounter,
866 "The safepoint id should be set only in block path");
867
868 // Check for pending. async. exceptions or suspends - except if the
869 // thread was blocked inside the VM. has_special_runtime_exit_condition()
870 // is called last since it grabs a lock and we only want to do that when
871 // we must.
872 //
873 // Note: we never deliver an async exception at a polling point as the
874 // compiler may not have an exception handler for it. The polling
875 // code will notice the async and deoptimize and the exception will
876 // be delivered. (Polling at a return point is ok though). Sure is
877 // a lot of bother for a deprecated feature...
878 //
879 // We don't deliver an async exception if the thread state is
880 // _thread_in_native_trans so JNI functions won't be called with
881 // a surprising pending exception. If the thread state is going back to java,
882 // async exception is checked in check_special_condition_for_native_trans().
883
884 if (state != _thread_blocked_trans &&
885 state != _thread_in_vm_trans &&
886 thread->has_special_runtime_exit_condition()) {
887 thread->handle_special_runtime_exit_condition(
888 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
889 }
890
891 // cross_modify_fence is done by SafepointMechanism::block_if_requested_slow
892 // which is the only caller here.
893 }
894
895 // ------------------------------------------------------------------------------------------------------
896 // Exception handlers
897
898
899 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
900 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
901 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
902 if (!ThreadLocalHandshakes) {
903 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
904 }
905
906 if (log_is_enabled(Info, safepoint, stats)) {
907 Atomic::inc(&_nof_threads_hit_polling_page);
908 }
909
910 ThreadSafepointState* state = thread->safepoint_state();
911
912 state->handle_polling_page_exception();
913 }
914
915
916 void SafepointSynchronize::print_safepoint_timeout() {
917 if (!timeout_error_printed) {
918 timeout_error_printed = true;
919 // Print out the thread info which didn't reach the safepoint for debugging
920 // purposes (useful when there are lots of threads in the debugger).
921 LogTarget(Warning, safepoint) lt;
922 if (lt.is_enabled()) {
923 ResourceMark rm;
924 LogStream ls(lt);
925
926 ls.cr();
927 ls.print_cr("# SafepointSynchronize::begin: Timeout detected:");
928 ls.print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
929 ls.print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
930 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) {
931 if (cur_thread->safepoint_state()->is_running()) {
932 ls.print("# ");
933 cur_thread->print_on(&ls);
934 ls.cr();
935 }
936 }
937 ls.print_cr("# SafepointSynchronize::begin: (End of list)");
938 }
939 }
940
941 // To debug the long safepoint, specify both AbortVMOnSafepointTimeout &
942 // ShowMessageBoxOnError.
943 if (AbortVMOnSafepointTimeout) {
944 // Send the blocking thread a signal to terminate and write an error file.
945 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) {
946 if (cur_thread->safepoint_state()->is_running()) {
947 if (!os::signal_thread(cur_thread, SIGILL, "blocking a safepoint")) {
948 break; // Could not send signal. Report fatal error.
949 }
950 // Give cur_thread a chance to report the error and terminate the VM.
951 os::sleep(Thread::current(), 3000, false);
952 }
953 }
954 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
955 SafepointTimeoutDelay, VMThread::vm_operation()->name());
956 }
957 }
958
959 // -------------------------------------------------------------------------------------------------------
960 // Implementation of ThreadSafepointState
961
962 ThreadSafepointState::ThreadSafepointState(JavaThread *thread)
963 : _at_poll_safepoint(false), _thread(thread), _safepoint_safe(false),
964 _safepoint_id(SafepointSynchronize::InactiveSafepointCounter), _next(NULL) {
965 }
966
967 void ThreadSafepointState::create(JavaThread *thread) {
968 ThreadSafepointState *state = new ThreadSafepointState(thread);
969 thread->set_safepoint_state(state);
970 }
971
972 void ThreadSafepointState::destroy(JavaThread *thread) {
973 if (thread->safepoint_state()) {
974 delete(thread->safepoint_state());
975 thread->set_safepoint_state(NULL);
976 }
977 }
978
979 uint64_t ThreadSafepointState::get_safepoint_id() const {
980 return OrderAccess::load_acquire(&_safepoint_id);
981 }
982
983 void ThreadSafepointState::reset_safepoint_id() {
984 OrderAccess::release_store(&_safepoint_id, SafepointSynchronize::InactiveSafepointCounter);
985 }
986
987 void ThreadSafepointState::set_safepoint_id(uint64_t safepoint_id) {
988 OrderAccess::release_store(&_safepoint_id, safepoint_id);
989 }
990
991 void ThreadSafepointState::examine_state_of_thread(uint64_t safepoint_count) {
992 assert(is_running(), "better be running or just have hit safepoint poll");
993
994 JavaThreadState stable_state;
995 if (!SafepointSynchronize::try_stable_load_state(&stable_state, _thread, safepoint_count)) {
996 // We could not get stable state of the JavaThread.
997 // Consider it running and just return.
998 return;
999 }
1000
1001 // Check for a thread that is suspended. Note that thread resume tries
1002 // to grab the Threads_lock which we own here, so a thread cannot be
1003 // resumed during safepoint synchronization.
1004
1005 // We check to see if this thread is suspended without locking to
1006 // avoid deadlocking with a third thread that is waiting for this
1007 // thread to be suspended. The third thread can notice the safepoint
1008 // that we're trying to start at the beginning of its SR_lock->wait()
1009 // call. If that happens, then the third thread will block on the
1010 // safepoint while still holding the underlying SR_lock. We won't be
1011 // able to get the SR_lock and we'll deadlock.
1012 //
1013 // We don't need to grab the SR_lock here for two reasons:
1014 // 1) The suspend flags are both volatile and are set with an
1015 // Atomic::cmpxchg() call so we should see the suspended
1016 // state right away.
1017 // 2) We're being called from the safepoint polling loop; if
1018 // we don't see the suspended state on this iteration, then
1019 // we'll come around again.
1020 //
1021 bool is_suspended = _thread->is_ext_suspended();
1022 if (is_suspended) {
1023 account_safe_thread();
1024 return;
1025 }
1026
1027 if (safepoint_safe_with(_thread, stable_state)) {
1028 check_for_lazy_critical_native(_thread, stable_state);
1029 account_safe_thread();
1030 return;
1031 }
1032
1033 // All other thread states will continue to run until they
1034 // transition and self-block in state _blocked
1035 // Safepoint polling in compiled code causes the Java threads to do the same.
1036 // Note: new threads may require a malloc so they must be allowed to finish
1037
1038 assert(is_running(), "examine_state_of_thread on non-running thread");
1039 return;
1040 }
1041
1042 void ThreadSafepointState::account_safe_thread() {
1043 SafepointSynchronize::decrement_waiting_to_block();
1044 if (_thread->in_critical()) {
1045 // Notice that this thread is in a critical section
1046 SafepointSynchronize::increment_jni_active_count();
1047 }
1048 DEBUG_ONLY(_thread->set_visited_for_critical_count(SafepointSynchronize::safepoint_counter());)
1049 assert(!_safepoint_safe, "Must be unsafe before safe");
1050 _safepoint_safe = true;
1051 }
1052
1053 void ThreadSafepointState::restart() {
1054 assert(_safepoint_safe, "Must be safe before unsafe");
1055 _safepoint_safe = false;
1056 }
1057
1058 void ThreadSafepointState::print_on(outputStream *st) const {
1059 const char *s = _safepoint_safe ? "_at_safepoint" : "_running";
1060
1061 st->print_cr("Thread: " INTPTR_FORMAT
1062 " [0x%2x] State: %s _at_poll_safepoint %d",
1063 p2i(_thread), _thread->osthread()->thread_id(), s, _at_poll_safepoint);
1064
1065 _thread->print_thread_state_on(st);
1066 }
1067
1068 // ---------------------------------------------------------------------------------------------------------------------
1069
1070 // Block the thread at poll or poll return for safepoint/handshake.
1071 void ThreadSafepointState::handle_polling_page_exception() {
1072
1073 // If we're using a global poll, then the thread should not be
1074 // marked as safepoint safe yet.
1075 assert(!SafepointMechanism::uses_global_page_poll() || !_safepoint_safe,
1076 "polling page exception on thread safepoint safe");
1077
1078 // Step 1: Find the nmethod from the return address
1079 address real_return_addr = thread()->saved_exception_pc();
1080
1081 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1082 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1083 CompiledMethod* nm = (CompiledMethod*)cb;
1084
1085 // Find frame of caller
1086 frame stub_fr = thread()->last_frame();
1087 CodeBlob* stub_cb = stub_fr.cb();
1088 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1089 RegisterMap map(thread(), true);
1090 frame caller_fr = stub_fr.sender(&map);
1091
1092 // Should only be poll_return or poll
1093 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1094
1095 // This is a poll immediately before a return. The exception handling code
1096 // has already had the effect of causing the return to occur, so the execution
1097 // will continue immediately after the call. In addition, the oopmap at the
1098 // return point does not mark the return value as an oop (if it is), so
1099 // it needs a handle here to be updated.
1100 if( nm->is_at_poll_return(real_return_addr) ) {
1101 // See if return type is an oop.
1102 bool return_oop = nm->method()->is_returning_oop();
1103 Handle return_value;
1104 if (return_oop) {
1105 // The oop result has been saved on the stack together with all
1106 // the other registers. In order to preserve it over GCs we need
1107 // to keep it in a handle.
1108 oop result = caller_fr.saved_oop_result(&map);
1109 assert(oopDesc::is_oop_or_null(result), "must be oop");
1110 return_value = Handle(thread(), result);
1111 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1112 }
1113
1114 // Block the thread
1115 SafepointMechanism::block_if_requested(thread());
1116
1117 // restore oop result, if any
1118 if (return_oop) {
1119 caller_fr.set_saved_oop_result(&map, return_value());
1120 }
1121 }
1122
1123 // This is a safepoint poll. Verify the return address and block.
1124 else {
1125 set_at_poll_safepoint(true);
1126
1127 // verify the blob built the "return address" correctly
1128 assert(real_return_addr == caller_fr.pc(), "must match");
1129
1130 // Block the thread
1131 SafepointMechanism::block_if_requested(thread());
1132 set_at_poll_safepoint(false);
1133
1134 // If we have a pending async exception deoptimize the frame
1135 // as otherwise we may never deliver it.
1136 if (thread()->has_async_condition()) {
1137 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1138 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1139 }
1140
1141 // If an exception has been installed we must check for a pending deoptimization
1142 // Deoptimize frame if exception has been thrown.
1143
1144 if (thread()->has_pending_exception() ) {
1145 RegisterMap map(thread(), true);
1146 frame caller_fr = stub_fr.sender(&map);
1147 if (caller_fr.is_deoptimized_frame()) {
1148 // The exception patch will destroy registers that are still
1149 // live and will be needed during deoptimization. Defer the
1150 // Async exception should have deferred the exception until the
1151 // next safepoint which will be detected when we get into
1152 // the interpreter so if we have an exception now things
1153 // are messed up.
1154
1155 fatal("Exception installed and deoptimization is pending");
1156 }
1157 }
1158 }
1159 }
1160
1161
1162 // -------------------------------------------------------------------------------------------------------
1163 // Implementation of SafepointTracing
1164
1165 jlong SafepointTracing::_last_safepoint_begin_time_ns = 0;
1166 jlong SafepointTracing::_last_safepoint_sync_time_ns = 0;
1167 jlong SafepointTracing::_last_safepoint_cleanup_time_ns = 0;
1168 jlong SafepointTracing::_last_safepoint_end_time_ns = 0;
1169 jlong SafepointTracing::_last_safepoint_end_time_epoch_ms = 0;
1170 jlong SafepointTracing::_last_app_time_ns = 0;
1171 int SafepointTracing::_nof_threads = 0;
1172 int SafepointTracing::_nof_running = 0;
1173 int SafepointTracing::_page_trap = 0;
1174 VM_Operation::VMOp_Type SafepointTracing::_current_type;
1175 jlong SafepointTracing::_max_sync_time = 0;
1176 jlong SafepointTracing::_max_vmop_time = 0;
1177 uint64_t SafepointTracing::_op_count[VM_Operation::VMOp_Terminating] = {0};
1178
1179 void SafepointTracing::init() {
1180 // Application start
1181 _last_safepoint_end_time_ns = os::javaTimeNanos();
1182 // amount of time since epoch
1183 _last_safepoint_end_time_epoch_ms = os::javaTimeMillis();
1184 }
1185
1186 // Helper method to print the header.
1187 static void print_header(outputStream* st) {
1188 // The number of spaces is significant here, and should match the format
1189 // specifiers in print_statistics().
1190
1191 st->print("VM Operation "
1192 "[ threads: total initial_running ]"
1193 "[ time: sync cleanup vmop total ]");
1194
1195 st->print_cr(" page_trap_count");
1196 }
1197
1198 // This prints a nice table. To get the statistics to not shift due to the logging uptime
1199 // decorator, use the option as: -Xlog:safepoint+stats:[outputfile]:none
1200 void SafepointTracing::statistics_log() {
1201 LogTarget(Info, safepoint, stats) lt;
1202 assert (lt.is_enabled(), "should only be called when printing statistics is enabled");
1203 LogStream ls(lt);
1204
1205 static int _cur_stat_index = 0;
1206
1207 // Print header every 30 entries
1208 if ((_cur_stat_index % 30) == 0) {
1209 print_header(&ls);
1210 _cur_stat_index = 1; // wrap
1211 } else {
1212 _cur_stat_index++;
1213 }
1214
1215 ls.print("%-28s [ "
1216 INT32_FORMAT_W(8) " " INT32_FORMAT_W(8) " "
1217 "]",
1218 VM_Operation::name(_current_type),
1219 _nof_threads,
1220 _nof_running);
1221 ls.print("[ "
1222 INT64_FORMAT_W(10) " " INT64_FORMAT_W(10) " "
1223 INT64_FORMAT_W(10) " " INT64_FORMAT_W(10) " ]",
1224 (int64_t)(_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns),
1225 (int64_t)(_last_safepoint_cleanup_time_ns - _last_safepoint_sync_time_ns),
1226 (int64_t)(_last_safepoint_end_time_ns - _last_safepoint_cleanup_time_ns),
1227 (int64_t)(_last_safepoint_end_time_ns - _last_safepoint_begin_time_ns));
1228
1229 ls.print_cr(INT32_FORMAT_W(16), _page_trap);
1230 }
1231
1232 // This method will be called when VM exits. This tries to summarize the sampling.
1233 // Current thread may already be deleted, so don't use ResourceMark.
1234 void SafepointTracing::statistics_exit_log() {
1235 if (!log_is_enabled(Info, safepoint, stats)) {
1236 return;
1237 }
1238 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1239 if (_op_count[index] != 0) {
1240 log_info(safepoint, stats)("%-28s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1241 _op_count[index]);
1242 }
1243 }
1244
1245 log_info(safepoint, stats)("VM operations coalesced during safepoint " INT64_FORMAT,
1246 VMThread::get_coalesced_count());
1247 log_info(safepoint, stats)("Maximum sync time " INT64_FORMAT" ns",
1248 (int64_t)(_max_sync_time));
1249 log_info(safepoint, stats)("Maximum vm operation time (except for Exit VM operation) "
1250 INT64_FORMAT " ns",
1251 (int64_t)(_max_vmop_time));
1252 }
1253
1254 void SafepointTracing::begin(VM_Operation::VMOp_Type type) {
1255 _op_count[type]++;
1256 _current_type = type;
1257
1258 // update the time stamp to begin recording safepoint time
1259 _last_safepoint_begin_time_ns = os::javaTimeNanos();
1260 _last_safepoint_sync_time_ns = 0;
1261 _last_safepoint_cleanup_time_ns = 0;
1262
1263 _last_app_time_ns = _last_safepoint_begin_time_ns - _last_safepoint_end_time_ns;
1264 _last_safepoint_end_time_ns = 0;
1265
1266 RuntimeService::record_safepoint_begin(_last_app_time_ns);
1267 }
1268
1269 void SafepointTracing::synchronized(int nof_threads, int nof_running, int traps) {
1270 _last_safepoint_sync_time_ns = os::javaTimeNanos();
1271 _nof_threads = nof_threads;
1272 _nof_running = nof_running;
1273 _page_trap = traps;
1274 RuntimeService::record_safepoint_synchronized(_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns);
1275 }
1276
1277 void SafepointTracing::cleanup() {
1278 _last_safepoint_cleanup_time_ns = os::javaTimeNanos();
1279 }
1280
1281 void SafepointTracing::end() {
1282 _last_safepoint_end_time_ns = os::javaTimeNanos();
1283 // amount of time since epoch
1284 _last_safepoint_end_time_epoch_ms = os::javaTimeMillis();
1285
1286 if (_max_sync_time < (_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns)) {
1287 _max_sync_time = _last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns;
1288 }
1289 if (_max_vmop_time < (_last_safepoint_end_time_ns - _last_safepoint_sync_time_ns)) {
1290 _max_vmop_time = _last_safepoint_end_time_ns - _last_safepoint_sync_time_ns;
1291 }
1292 if (log_is_enabled(Info, safepoint, stats)) {
1293 statistics_log();
1294 }
1295
1296 log_info(safepoint)(
1297 "Safepoint \"%s\", "
1298 "Time since last: " JLONG_FORMAT " ns, "
1299 "Reaching safepoint: " JLONG_FORMAT " ns, "
1300 "At safepoint: " JLONG_FORMAT " ns, "
1301 "Total: " JLONG_FORMAT " ns",
1302 VM_Operation::name(_current_type),
1303 _last_app_time_ns,
1304 _last_safepoint_cleanup_time_ns - _last_safepoint_begin_time_ns,
1305 _last_safepoint_end_time_ns - _last_safepoint_cleanup_time_ns,
1306 _last_safepoint_end_time_ns - _last_safepoint_begin_time_ns
1307 );
1308
1309 RuntimeService::record_safepoint_end(_last_safepoint_end_time_ns - _last_safepoint_cleanup_time_ns);
1310 }