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
481 SafepointMechanism::disarm_if_needed(current, false /* NO release */);
482 }
483 } // ~JavaThreadIteratorWithHandle
484
485 // Release threads lock, so threads can be created/destroyed again.
486 Threads_lock->unlock();
487
488 // Wake threads after local state is correctly set.
489 _wait_barrier->disarm();
490 }
491
492 // Wake up all threads, so they are ready to resume execution after the safepoint
493 // operation has been carried out
494 void SafepointSynchronize::end() {
495 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
496 EventSafepointEnd event;
497 uint64_t safepoint_id = _safepoint_counter;
498 assert(Thread::current()->is_VM_thread(), "Only VM thread can execute a safepoint");
499
500 disarm_safepoint();
501
502 Universe::heap()->safepoint_synchronize_end();
503
504 SafepointTracing::end();
505
506 post_safepoint_end_event(event, safepoint_id);
507 }
508
509 bool SafepointSynchronize::is_cleanup_needed() {
510 // Need a safepoint if there are many monitors to deflate.
511 if (ObjectSynchronizer::is_cleanup_needed()) return true;
512 // Need a safepoint if some inline cache buffers is non-empty
513 if (!InlineCacheBuffer::is_empty()) return true;
514 return false;
515 }
516
517 class ParallelSPCleanupThreadClosure : public ThreadClosure {
518 private:
519 CodeBlobClosure* _nmethod_cl;
520 DeflateMonitorCounters* _counters;
521
522 public:
523 ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) :
524 _nmethod_cl(UseCodeAging ? NMethodSweeper::prepare_reset_hotness_counters() : NULL),
525 _counters(counters) {}
526
527 void do_thread(Thread* thread) {
528 // deflate_thread_local_monitors() handles or requests deflation of
529 // this thread's idle monitors. If !AsyncDeflateIdleMonitors or if
530 // there is a special cleanup request, deflation is handled now.
531 // Otherwise, async deflation is requested via a flag.
532 ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters);
533 if (_nmethod_cl != NULL && thread->is_Java_thread() &&
534 ! thread->is_Code_cache_sweeper_thread()) {
535 JavaThread* jt = (JavaThread*) thread;
536 jt->nmethods_do(_nmethod_cl);
537 }
538 }
539 };
540
541 class ParallelSPCleanupTask : public AbstractGangTask {
542 private:
543 SubTasksDone _subtasks;
544 ParallelSPCleanupThreadClosure _cleanup_threads_cl;
545 uint _num_workers;
546 DeflateMonitorCounters* _counters;
547 public:
548 ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
549 AbstractGangTask("Parallel Safepoint Cleanup"),
550 _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)),
551 _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
552 _num_workers(num_workers),
553 _counters(counters) {}
554
555 void work(uint worker_id) {
556 uint64_t safepoint_id = SafepointSynchronize::safepoint_counter();
557 // All threads deflate monitors and mark nmethods (if necessary).
558 Threads::possibly_parallel_threads_do(true, &_cleanup_threads_cl);
559
560 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
561 const char* name = "deflating global idle monitors";
562 EventSafepointCleanupTask event;
563 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
564 // AsyncDeflateIdleMonitors only uses DeflateMonitorCounters
565 // when a special cleanup has been requested.
566 // Note: This logging output will include global idle monitor
567 // elapsed times, but not global idle monitor deflation count.
568 ObjectSynchronizer::do_safepoint_work(_counters);
569
570 post_safepoint_cleanup_task_event(event, safepoint_id, name);
571 }
572
573 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
574 const char* name = "updating inline caches";
575 EventSafepointCleanupTask event;
576 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
577 InlineCacheBuffer::update_inline_caches();
578
579 post_safepoint_cleanup_task_event(event, safepoint_id, name);
580 }
581
582 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
583 const char* name = "compilation policy safepoint handler";
584 EventSafepointCleanupTask event;
585 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
586 CompilationPolicy::policy()->do_safepoint_work();
587
588 post_safepoint_cleanup_task_event(event, safepoint_id, name);
589 }
590
591 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
592 if (SymbolTable::needs_rehashing()) {
593 const char* name = "rehashing symbol table";
594 EventSafepointCleanupTask event;
595 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
596 SymbolTable::rehash_table();
597
598 post_safepoint_cleanup_task_event(event, safepoint_id, name);
599 }
600 }
601
602 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
603 if (StringTable::needs_rehashing()) {
604 const char* name = "rehashing string table";
605 EventSafepointCleanupTask event;
606 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
607 StringTable::rehash_table();
608
609 post_safepoint_cleanup_task_event(event, safepoint_id, name);
610 }
611 }
612
613 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) {
614 // CMS delays purging the CLDG until the beginning of the next safepoint and to
615 // make sure concurrent sweep is done
616 const char* name = "purging class loader data graph";
617 EventSafepointCleanupTask event;
618 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
619 ClassLoaderDataGraph::purge_if_needed();
620
621 post_safepoint_cleanup_task_event(event, safepoint_id, name);
622 }
623
624 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_SYSTEM_DICTIONARY_RESIZE)) {
625 const char* name = "resizing system dictionaries";
626 EventSafepointCleanupTask event;
627 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
628 ClassLoaderDataGraph::resize_if_needed();
629
630 post_safepoint_cleanup_task_event(event, safepoint_id, name);
631 }
632
633 _subtasks.all_tasks_completed(_num_workers);
634 }
635 };
636
637 // Various cleaning tasks that should be done periodically at safepoints.
638 void SafepointSynchronize::do_cleanup_tasks() {
639
640 TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup));
641
642 // Prepare for monitor deflation.
643 DeflateMonitorCounters deflate_counters;
644 ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
645
646 CollectedHeap* heap = Universe::heap();
647 assert(heap != NULL, "heap not initialized yet?");
648 WorkGang* cleanup_workers = heap->get_safepoint_workers();
649 if (cleanup_workers != NULL) {
650 // Parallel cleanup using GC provided thread pool.
651 uint num_cleanup_workers = cleanup_workers->active_workers();
652 ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
653 StrongRootsScope srs(num_cleanup_workers);
654 cleanup_workers->run_task(&cleanup);
655 } else {
656 // Serial cleanup using VMThread.
657 ParallelSPCleanupTask cleanup(1, &deflate_counters);
658 StrongRootsScope srs(1);
659 cleanup.work(0);
660 }
661
662 // Needs to be done single threaded by the VMThread. This walks
663 // the thread stacks looking for references to metadata before
664 // deciding to remove it from the metaspaces.
665 if (ClassLoaderDataGraph::should_clean_metaspaces_and_reset()) {
666 const char* name = "cleanup live ClassLoaderData metaspaces";
667 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
668 ClassLoaderDataGraph::walk_metadata_and_clean_metaspaces();
669 }
670
671 // Finish monitor deflation.
672 ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
673
674 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
675 }
676
677 // Methods for determining if a JavaThread is safepoint safe.
678
679 // False means unsafe with undetermined state.
680 // True means a determined state, but it may be an unsafe state.
681 // If called from a non-safepoint context safepoint_count MUST be InactiveSafepointCounter.
682 bool SafepointSynchronize::try_stable_load_state(JavaThreadState *state, JavaThread *thread, uint64_t safepoint_count) {
683 assert((safepoint_count != InactiveSafepointCounter &&
684 Thread::current() == (Thread*)VMThread::vm_thread() &&
685 SafepointSynchronize::_state != _not_synchronized)
686 || safepoint_count == InactiveSafepointCounter, "Invalid check");
687
688 // To handle the thread_blocked state on the backedge of the WaitBarrier from
689 // previous safepoint and reading the reset value (0/InactiveSafepointCounter) we
690 // re-read state after we read thread safepoint id. The JavaThread changes its
691 // thread state from thread_blocked before resetting safepoint id to 0.
692 // This guarantees the second read will be from an updated thread state. It can
693 // either be different state making this an unsafe state or it can see blocked
694 // again. When we see blocked twice with a 0 safepoint id, either:
695 // - It is normally blocked, e.g. on Mutex, TBIVM.
696 // - It was in SS:block(), looped around to SS:block() and is blocked on the WaitBarrier.
697 // - It was in SS:block() but now on a Mutex.
698 // All of these cases are safe.
699
700 *state = thread->thread_state();
701 OrderAccess::loadload();
702 uint64_t sid = thread->safepoint_state()->get_safepoint_id(); // Load acquire
703 if (sid != InactiveSafepointCounter && sid != safepoint_count) {
704 // In an old safepoint, state not relevant.
705 return false;
706 }
707 return *state == thread->thread_state();
708 }
709
710 static bool safepoint_safe_with(JavaThread *thread, JavaThreadState state) {
711 switch(state) {
712 case _thread_in_native:
713 // native threads are safe if they have no java stack or have walkable stack
714 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
715
716 case _thread_blocked:
717 // On wait_barrier or blocked.
718 // Blocked threads should already have walkable stack.
719 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
720 return true;
721
722 default:
723 return false;
724 }
725 }
726
727 bool SafepointSynchronize::handshake_safe(JavaThread *thread) {
728 // This function must be called with the Threads_lock held so an externally
729 // suspended thread cannot be resumed thus it is safe.
730 assert(Threads_lock->owned_by_self() && Thread::current()->is_VM_thread(),
731 "Must hold Threads_lock and be VMThread");
732 if (thread->is_ext_suspended() || thread->is_terminated()) {
733 return true;
734 }
735 JavaThreadState stable_state;
736 if (try_stable_load_state(&stable_state, thread, InactiveSafepointCounter)) {
737 return safepoint_safe_with(thread, stable_state);
738 }
739 return false;
740 }
741
742 // See if the thread is running inside a lazy critical native and
743 // update the thread critical count if so. Also set a suspend flag to
744 // cause the native wrapper to return into the JVM to do the unlock
745 // once the native finishes.
746 static void check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
747 if (state == _thread_in_native &&
748 thread->has_last_Java_frame() &&
749 thread->frame_anchor()->walkable()) {
750 // This thread might be in a critical native nmethod so look at
751 // the top of the stack and increment the critical count if it
752 // is.
753 frame wrapper_frame = thread->last_frame();
754 CodeBlob* stub_cb = wrapper_frame.cb();
755 if (stub_cb != NULL &&
756 stub_cb->is_nmethod() &&
757 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
758 // A thread could potentially be in a critical native across
759 // more than one safepoint, so only update the critical state on
760 // the first one. When it returns it will perform the unlock.
761 if (!thread->do_critical_native_unlock()) {
762 #ifdef ASSERT
763 if (!thread->in_critical()) {
764 GCLocker::increment_debug_jni_lock_count();
765 }
766 #endif
767 thread->enter_critical();
768 // Make sure the native wrapper calls back on return to
769 // perform the needed critical unlock.
770 thread->set_critical_native_unlock();
771 }
772 }
773 }
774 }
775
776 // -------------------------------------------------------------------------------------------------------
777 // Implementation of Safepoint blocking point
778
779 void SafepointSynchronize::block(JavaThread *thread) {
780 assert(thread != NULL, "thread must be set");
781 assert(thread->is_Java_thread(), "not a Java thread");
782
783 // Threads shouldn't block if they are in the middle of printing, but...
784 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
785
786 // Only bail from the block() call if the thread is gone from the
787 // thread list; starting to exit should still block.
788 if (thread->is_terminated()) {
789 // block current thread if we come here from native code when VM is gone
790 thread->block_if_vm_exited();
791
792 // otherwise do nothing
793 return;
794 }
795
796 JavaThreadState state = thread->thread_state();
797 thread->frame_anchor()->make_walkable(thread);
798
799 uint64_t safepoint_id = SafepointSynchronize::safepoint_counter();
800 // Check that we have a valid thread_state at this point
801 switch(state) {
802 case _thread_in_vm_trans:
803 case _thread_in_Java: // From compiled code
804 case _thread_in_native_trans:
805 case _thread_blocked_trans:
806 case _thread_new_trans:
807
808 // We have no idea where the VMThread is, it might even be at next safepoint.
809 // So we can miss this poll, but stop at next.
810
811 // Load dependent store, it must not pass loading of safepoint_id.
812 thread->safepoint_state()->set_safepoint_id(safepoint_id); // Release store
813
814 // This part we can skip if we notice we miss or are in a future safepoint.
815 OrderAccess::storestore();
816 // Load in wait barrier should not float up
817 thread->set_thread_state_fence(_thread_blocked);
818
819 _wait_barrier->wait(static_cast<int>(safepoint_id));
820 assert(_state != _synchronized, "Can't be");
821
822 // If barrier is disarmed stop store from floating above loads in barrier.
823 OrderAccess::loadstore();
824 thread->set_thread_state(state);
825
826 // Then we reset the safepoint id to inactive.
827 thread->safepoint_state()->reset_safepoint_id(); // Release store
828
829 OrderAccess::fence();
830
831 break;
832
833 default:
834 fatal("Illegal threadstate encountered: %d", state);
835 }
836 guarantee(thread->safepoint_state()->get_safepoint_id() == InactiveSafepointCounter,
837 "The safepoint id should be set only in block path");
838
839 // Check for pending. async. exceptions or suspends - except if the
840 // thread was blocked inside the VM. has_special_runtime_exit_condition()
841 // is called last since it grabs a lock and we only want to do that when
842 // we must.
843 //
844 // Note: we never deliver an async exception at a polling point as the
845 // compiler may not have an exception handler for it. The polling
846 // code will notice the async and deoptimize and the exception will
847 // be delivered. (Polling at a return point is ok though). Sure is
848 // a lot of bother for a deprecated feature...
849 //
850 // We don't deliver an async exception if the thread state is
851 // _thread_in_native_trans so JNI functions won't be called with
852 // a surprising pending exception. If the thread state is going back to java,
853 // async exception is checked in check_special_condition_for_native_trans().
854
855 if (state != _thread_blocked_trans &&
856 state != _thread_in_vm_trans &&
857 thread->has_special_runtime_exit_condition()) {
858 thread->handle_special_runtime_exit_condition(
859 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
860 }
861
862 // cross_modify_fence is done by SafepointMechanism::block_if_requested_slow
863 // which is the only caller here.
864 }
865
866 // ------------------------------------------------------------------------------------------------------
867 // Exception handlers
868
869
870 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
871 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
872 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
873 if (!ThreadLocalHandshakes) {
874 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
875 }
876
877 if (log_is_enabled(Info, safepoint, stats)) {
878 Atomic::inc(&_nof_threads_hit_polling_page);
879 }
880
881 ThreadSafepointState* state = thread->safepoint_state();
882
883 state->handle_polling_page_exception();
884 }
885
886
887 void SafepointSynchronize::print_safepoint_timeout() {
888 if (!timeout_error_printed) {
889 timeout_error_printed = true;
890 // Print out the thread info which didn't reach the safepoint for debugging
891 // purposes (useful when there are lots of threads in the debugger).
892 LogTarget(Warning, safepoint) lt;
893 if (lt.is_enabled()) {
894 ResourceMark rm;
895 LogStream ls(lt);
896
897 ls.cr();
898 ls.print_cr("# SafepointSynchronize::begin: Timeout detected:");
899 ls.print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
900 ls.print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
901 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) {
902 if (cur_thread->safepoint_state()->is_running()) {
903 ls.print("# ");
904 cur_thread->print_on(&ls);
905 ls.cr();
906 }
907 }
908 ls.print_cr("# SafepointSynchronize::begin: (End of list)");
909 }
910 }
911
912 // To debug the long safepoint, specify both AbortVMOnSafepointTimeout &
913 // ShowMessageBoxOnError.
914 if (AbortVMOnSafepointTimeout) {
915 // Send the blocking thread a signal to terminate and write an error file.
916 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) {
917 if (cur_thread->safepoint_state()->is_running()) {
918 if (!os::signal_thread(cur_thread, SIGILL, "blocking a safepoint")) {
919 break; // Could not send signal. Report fatal error.
920 }
921 // Give cur_thread a chance to report the error and terminate the VM.
922 os::sleep(Thread::current(), 3000, false);
923 }
924 }
925 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
926 SafepointTimeoutDelay, VMThread::vm_operation()->name());
927 }
928 }
929
930 // -------------------------------------------------------------------------------------------------------
931 // Implementation of ThreadSafepointState
932
933 ThreadSafepointState::ThreadSafepointState(JavaThread *thread)
934 : _at_poll_safepoint(false), _thread(thread), _safepoint_safe(false),
935 _safepoint_id(SafepointSynchronize::InactiveSafepointCounter),
936 _orig_thread_state(_thread_uninitialized), _next(NULL) {
937 }
938
939 void ThreadSafepointState::create(JavaThread *thread) {
940 ThreadSafepointState *state = new ThreadSafepointState(thread);
941 thread->set_safepoint_state(state);
942 }
943
944 void ThreadSafepointState::destroy(JavaThread *thread) {
945 if (thread->safepoint_state()) {
946 delete(thread->safepoint_state());
947 thread->set_safepoint_state(NULL);
948 }
949 }
950
951 uint64_t ThreadSafepointState::get_safepoint_id() const {
952 return OrderAccess::load_acquire(&_safepoint_id);
953 }
954
955 void ThreadSafepointState::reset_safepoint_id() {
956 OrderAccess::release_store(&_safepoint_id, SafepointSynchronize::InactiveSafepointCounter);
957 }
958
959 void ThreadSafepointState::set_safepoint_id(uint64_t safepoint_id) {
960 OrderAccess::release_store(&_safepoint_id, safepoint_id);
961 }
962
963 void ThreadSafepointState::examine_state_of_thread(uint64_t safepoint_count) {
964 assert(is_running(), "better be running or just have hit safepoint poll");
965
966 JavaThreadState stable_state;
967 if (!SafepointSynchronize::try_stable_load_state(&stable_state, _thread, safepoint_count)) {
968 // We could not get stable state of the JavaThread.
969 // Consider it running and just return.
970 return;
971 }
972
973 // Save the state at the start of safepoint processing.
974 _orig_thread_state = stable_state;
975
976 // Check for a thread that is suspended. Note that thread resume tries
977 // to grab the Threads_lock which we own here, so a thread cannot be
978 // resumed during safepoint synchronization.
979
980 // We check to see if this thread is suspended without locking to
981 // avoid deadlocking with a third thread that is waiting for this
982 // thread to be suspended. The third thread can notice the safepoint
983 // that we're trying to start at the beginning of its SR_lock->wait()
984 // call. If that happens, then the third thread will block on the
985 // safepoint while still holding the underlying SR_lock. We won't be
986 // able to get the SR_lock and we'll deadlock.
987 //
988 // We don't need to grab the SR_lock here for two reasons:
989 // 1) The suspend flags are both volatile and are set with an
990 // Atomic::cmpxchg() call so we should see the suspended
991 // state right away.
992 // 2) We're being called from the safepoint polling loop; if
993 // we don't see the suspended state on this iteration, then
994 // we'll come around again.
995 //
996 bool is_suspended = _thread->is_ext_suspended();
997 if (is_suspended) {
998 account_safe_thread();
999 return;
1000 }
1001
1002 if (safepoint_safe_with(_thread, stable_state)) {
1003 check_for_lazy_critical_native(_thread, stable_state);
1004 account_safe_thread();
1005 return;
1006 }
1007
1008 // All other thread states will continue to run until they
1009 // transition and self-block in state _blocked
1010 // Safepoint polling in compiled code causes the Java threads to do the same.
1011 // Note: new threads may require a malloc so they must be allowed to finish
1012
1013 assert(is_running(), "examine_state_of_thread on non-running thread");
1014 return;
1015 }
1016
1017 void ThreadSafepointState::account_safe_thread() {
1018 SafepointSynchronize::decrement_waiting_to_block();
1019 if (_thread->in_critical()) {
1020 // Notice that this thread is in a critical section
1021 SafepointSynchronize::increment_jni_active_count();
1022 }
1023 DEBUG_ONLY(_thread->set_visited_for_critical_count(SafepointSynchronize::safepoint_counter());)
1024 assert(!_safepoint_safe, "Must be unsafe before safe");
1025 _safepoint_safe = true;
1026 }
1027
1028 void ThreadSafepointState::restart() {
1029 assert(_safepoint_safe, "Must be safe before unsafe");
1030 _safepoint_safe = false;
1031 }
1032
1033 void ThreadSafepointState::print_on(outputStream *st) const {
1034 const char *s = _safepoint_safe ? "_at_safepoint" : "_running";
1035
1036 st->print_cr("Thread: " INTPTR_FORMAT
1037 " [0x%2x] State: %s _at_poll_safepoint %d",
1038 p2i(_thread), _thread->osthread()->thread_id(), s, _at_poll_safepoint);
1039
1040 _thread->print_thread_state_on(st);
1041 }
1042
1043 // ---------------------------------------------------------------------------------------------------------------------
1044
1045 // Block the thread at poll or poll return for safepoint/handshake.
1046 void ThreadSafepointState::handle_polling_page_exception() {
1047
1048 // If we're using a global poll, then the thread should not be
1049 // marked as safepoint safe yet.
1050 assert(!SafepointMechanism::uses_global_page_poll() || !_safepoint_safe,
1051 "polling page exception on thread safepoint safe");
1052
1053 // Step 1: Find the nmethod from the return address
1054 address real_return_addr = thread()->saved_exception_pc();
1055
1056 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1057 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1058 CompiledMethod* nm = (CompiledMethod*)cb;
1059
1060 // Find frame of caller
1061 frame stub_fr = thread()->last_frame();
1062 CodeBlob* stub_cb = stub_fr.cb();
1063 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1064 RegisterMap map(thread(), true);
1065 frame caller_fr = stub_fr.sender(&map);
1066
1067 // Should only be poll_return or poll
1068 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1069
1070 // This is a poll immediately before a return. The exception handling code
1071 // has already had the effect of causing the return to occur, so the execution
1072 // will continue immediately after the call. In addition, the oopmap at the
1073 // return point does not mark the return value as an oop (if it is), so
1074 // it needs a handle here to be updated.
1075 if( nm->is_at_poll_return(real_return_addr) ) {
1076 // See if return type is an oop.
1077 bool return_oop = nm->method()->is_returning_oop();
1078 Handle return_value;
1079 if (return_oop) {
1080 // The oop result has been saved on the stack together with all
1081 // the other registers. In order to preserve it over GCs we need
1082 // to keep it in a handle.
1083 oop result = caller_fr.saved_oop_result(&map);
1084 assert(oopDesc::is_oop_or_null(result), "must be oop");
1085 return_value = Handle(thread(), result);
1086 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1087 }
1088
1089 // Block the thread
1090 SafepointMechanism::block_if_requested(thread());
1091
1092 // restore oop result, if any
1093 if (return_oop) {
1094 caller_fr.set_saved_oop_result(&map, return_value());
1095 }
1096 }
1097
1098 // This is a safepoint poll. Verify the return address and block.
1099 else {
1100 set_at_poll_safepoint(true);
1101
1102 // verify the blob built the "return address" correctly
1103 assert(real_return_addr == caller_fr.pc(), "must match");
1104
1105 // Block the thread
1106 SafepointMechanism::block_if_requested(thread());
1107 set_at_poll_safepoint(false);
1108
1109 // If we have a pending async exception deoptimize the frame
1110 // as otherwise we may never deliver it.
1111 if (thread()->has_async_condition()) {
1112 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1113 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1114 }
1115
1116 // If an exception has been installed we must check for a pending deoptimization
1117 // Deoptimize frame if exception has been thrown.
1118
1119 if (thread()->has_pending_exception() ) {
1120 RegisterMap map(thread(), true);
1121 frame caller_fr = stub_fr.sender(&map);
1122 if (caller_fr.is_deoptimized_frame()) {
1123 // The exception patch will destroy registers that are still
1124 // live and will be needed during deoptimization. Defer the
1125 // Async exception should have deferred the exception until the
1126 // next safepoint which will be detected when we get into
1127 // the interpreter so if we have an exception now things
1128 // are messed up.
1129
1130 fatal("Exception installed and deoptimization is pending");
1131 }
1132 }
1133 }
1134 }
1135
1136
1137 // -------------------------------------------------------------------------------------------------------
1138 // Implementation of SafepointTracing
1139
1140 jlong SafepointTracing::_last_safepoint_begin_time_ns = 0;
1141 jlong SafepointTracing::_last_safepoint_sync_time_ns = 0;
1142 jlong SafepointTracing::_last_safepoint_cleanup_time_ns = 0;
1143 jlong SafepointTracing::_last_safepoint_end_time_ns = 0;
1144 jlong SafepointTracing::_last_safepoint_end_time_epoch_ms = 0;
1145 jlong SafepointTracing::_last_app_time_ns = 0;
1146 int SafepointTracing::_nof_threads = 0;
1147 int SafepointTracing::_nof_running = 0;
1148 int SafepointTracing::_page_trap = 0;
1149 VM_Operation::VMOp_Type SafepointTracing::_current_type;
1150 jlong SafepointTracing::_max_sync_time = 0;
1151 jlong SafepointTracing::_max_vmop_time = 0;
1152 uint64_t SafepointTracing::_op_count[VM_Operation::VMOp_Terminating] = {0};
1153
1154 void SafepointTracing::init() {
1155 // Application start
1156 _last_safepoint_end_time_ns = os::javaTimeNanos();
1157 // amount of time since epoch
1158 _last_safepoint_end_time_epoch_ms = os::javaTimeMillis();
1159 }
1160
1161 // Helper method to print the header.
1162 static void print_header(outputStream* st) {
1163 // The number of spaces is significant here, and should match the format
1164 // specifiers in print_statistics().
1165
1166 st->print("VM Operation "
1167 "[ threads: total initial_running ]"
1168 "[ time: sync cleanup vmop total ]");
1169
1170 st->print_cr(" page_trap_count");
1171 }
1172
1173 // This prints a nice table. To get the statistics to not shift due to the logging uptime
1174 // decorator, use the option as: -Xlog:safepoint+stats:[outputfile]:none
1175 void SafepointTracing::statistics_log() {
1176 LogTarget(Info, safepoint, stats) lt;
1177 assert (lt.is_enabled(), "should only be called when printing statistics is enabled");
1178 LogStream ls(lt);
1179
1180 static int _cur_stat_index = 0;
1181
1182 // Print header every 30 entries
1183 if ((_cur_stat_index % 30) == 0) {
1184 print_header(&ls);
1185 _cur_stat_index = 1; // wrap
1186 } else {
1187 _cur_stat_index++;
1188 }
1189
1190 ls.print("%-28s [ "
1191 INT32_FORMAT_W(8) " " INT32_FORMAT_W(8) " "
1192 "]",
1193 VM_Operation::name(_current_type),
1194 _nof_threads,
1195 _nof_running);
1196 ls.print("[ "
1197 INT64_FORMAT_W(10) " " INT64_FORMAT_W(10) " "
1198 INT64_FORMAT_W(10) " " INT64_FORMAT_W(10) " ]",
1199 (int64_t)(_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns),
1200 (int64_t)(_last_safepoint_cleanup_time_ns - _last_safepoint_sync_time_ns),
1201 (int64_t)(_last_safepoint_end_time_ns - _last_safepoint_cleanup_time_ns),
1202 (int64_t)(_last_safepoint_end_time_ns - _last_safepoint_begin_time_ns));
1203
1204 ls.print_cr(INT32_FORMAT_W(16), _page_trap);
1205 }
1206
1207 // This method will be called when VM exits. This tries to summarize the sampling.
1208 // Current thread may already be deleted, so don't use ResourceMark.
1209 void SafepointTracing::statistics_exit_log() {
1210 if (!log_is_enabled(Info, safepoint, stats)) {
1211 return;
1212 }
1213 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1214 if (_op_count[index] != 0) {
1215 log_info(safepoint, stats)("%-28s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1216 _op_count[index]);
1217 }
1218 }
1219
1220 log_info(safepoint, stats)("VM operations coalesced during safepoint " INT64_FORMAT,
1221 VMThread::get_coalesced_count());
1222 log_info(safepoint, stats)("Maximum sync time " INT64_FORMAT" ns",
1223 (int64_t)(_max_sync_time));
1224 log_info(safepoint, stats)("Maximum vm operation time (except for Exit VM operation) "
1225 INT64_FORMAT " ns",
1226 (int64_t)(_max_vmop_time));
1227 }
1228
1229 void SafepointTracing::begin(VM_Operation::VMOp_Type type) {
1230 _op_count[type]++;
1231 _current_type = type;
1232
1233 // update the time stamp to begin recording safepoint time
1234 _last_safepoint_begin_time_ns = os::javaTimeNanos();
1235 _last_safepoint_sync_time_ns = 0;
1236 _last_safepoint_cleanup_time_ns = 0;
1237
1238 _last_app_time_ns = _last_safepoint_begin_time_ns - _last_safepoint_end_time_ns;
1239 _last_safepoint_end_time_ns = 0;
1240
1241 RuntimeService::record_safepoint_begin(_last_app_time_ns);
1242 }
1243
1244 void SafepointTracing::synchronized(int nof_threads, int nof_running, int traps) {
1245 _last_safepoint_sync_time_ns = os::javaTimeNanos();
1246 _nof_threads = nof_threads;
1247 _nof_running = nof_running;
1248 _page_trap = traps;
1249 RuntimeService::record_safepoint_synchronized(_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns);
1250 }
1251
1252 void SafepointTracing::cleanup() {
1253 _last_safepoint_cleanup_time_ns = os::javaTimeNanos();
1254 }
1255
1256 void SafepointTracing::end() {
1257 _last_safepoint_end_time_ns = os::javaTimeNanos();
1258 // amount of time since epoch
1259 _last_safepoint_end_time_epoch_ms = os::javaTimeMillis();
1260
1261 if (_max_sync_time < (_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns)) {
1262 _max_sync_time = _last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns;
1263 }
1264 if (_max_vmop_time < (_last_safepoint_end_time_ns - _last_safepoint_sync_time_ns)) {
1265 _max_vmop_time = _last_safepoint_end_time_ns - _last_safepoint_sync_time_ns;
1266 }
1267 if (log_is_enabled(Info, safepoint, stats)) {
1268 statistics_log();
1269 }
1270
1271 log_info(safepoint)(
1272 "Safepoint \"%s\", "
1273 "Time since last: " JLONG_FORMAT " ns, "
1274 "Reaching safepoint: " JLONG_FORMAT " ns, "
1275 "At safepoint: " JLONG_FORMAT " ns, "
1276 "Total: " JLONG_FORMAT " ns",
1277 VM_Operation::name(_current_type),
1278 _last_app_time_ns,
1279 _last_safepoint_cleanup_time_ns - _last_safepoint_begin_time_ns,
1280 _last_safepoint_end_time_ns - _last_safepoint_cleanup_time_ns,
1281 _last_safepoint_end_time_ns - _last_safepoint_begin_time_ns
1282 );
1283
1284 RuntimeService::record_safepoint_end(_last_safepoint_end_time_ns - _last_safepoint_cleanup_time_ns);
1285 }