1 /*
2 * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/stringTable.hpp"
27 #include "classfile/systemDictionary.hpp"
28 #include "code/codeCache.hpp"
29 #include "code/icBuffer.hpp"
30 #include "code/nmethod.hpp"
31 #include "code/pcDesc.hpp"
32 #include "code/scopeDesc.hpp"
33 #include "gc_interface/collectedHeap.hpp"
34 #include "interpreter/interpreter.hpp"
35 #include "memory/resourceArea.hpp"
36 #include "memory/universe.inline.hpp"
37 #include "oops/oop.inline.hpp"
38 #include "oops/symbol.hpp"
39 #include "runtime/compilationPolicy.hpp"
40 #include "runtime/deoptimization.hpp"
41 #include "runtime/frame.inline.hpp"
42 #include "runtime/interfaceSupport.hpp"
43 #include "runtime/mutexLocker.hpp"
44 #include "runtime/orderAccess.inline.hpp"
45 #include "runtime/osThread.hpp"
46 #include "runtime/safepoint.hpp"
47 #include "runtime/signature.hpp"
48 #include "runtime/stubCodeGenerator.hpp"
49 #include "runtime/stubRoutines.hpp"
50 #include "runtime/sweeper.hpp"
51 #include "runtime/synchronizer.hpp"
52 #include "runtime/thread.inline.hpp"
53 #include "services/memTracker.hpp"
54 #include "services/runtimeService.hpp"
55 #include "utilities/events.hpp"
56 #include "utilities/macros.hpp"
57 #ifdef TARGET_ARCH_x86
58 # include "nativeInst_x86.hpp"
59 # include "vmreg_x86.inline.hpp"
60 #endif
61 #ifdef TARGET_ARCH_sparc
62 # include "nativeInst_sparc.hpp"
63 # include "vmreg_sparc.inline.hpp"
64 #endif
65 #ifdef TARGET_ARCH_zero
66 # include "nativeInst_zero.hpp"
67 # include "vmreg_zero.inline.hpp"
68 #endif
69 #ifdef TARGET_ARCH_arm
70 # include "nativeInst_arm.hpp"
71 # include "vmreg_arm.inline.hpp"
72 #endif
73 #ifdef TARGET_ARCH_ppc
74 # include "nativeInst_ppc.hpp"
75 # include "vmreg_ppc.inline.hpp"
76 #endif
77 #if INCLUDE_ALL_GCS
78 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
79 #include "gc_implementation/shared/suspendibleThreadSet.hpp"
80 #endif // INCLUDE_ALL_GCS
81 #ifdef COMPILER1
82 #include "c1/c1_globals.hpp"
83 #endif
84
85 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
86
87 // --------------------------------------------------------------------------------------------------
88 // Implementation of Safepoint begin/end
89
90 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
91 volatile int SafepointSynchronize::_waiting_to_block = 0;
92 volatile int SafepointSynchronize::_safepoint_counter = 0;
93 int SafepointSynchronize::_current_jni_active_count = 0;
94 long SafepointSynchronize::_end_of_last_safepoint = 0;
95 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
96 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
97 static bool timeout_error_printed = false;
98
99 // Roll all threads forward to a safepoint and suspend them all
100 void SafepointSynchronize::begin() {
101
102 Thread* myThread = Thread::current();
103 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
104
105 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
106 _safepoint_begin_time = os::javaTimeNanos();
107 _ts_of_current_safepoint = tty->time_stamp().seconds();
108 }
109
110 #if INCLUDE_ALL_GCS
111 if (UseConcMarkSweepGC) {
112 // In the future we should investigate whether CMS can use the
113 // more-general mechanism below. DLD (01/05).
114 ConcurrentMarkSweepThread::synchronize(false);
115 } else if (UseG1GC) {
116 SuspendibleThreadSet::synchronize();
117 }
118 #endif // INCLUDE_ALL_GCS
119
120 // By getting the Threads_lock, we assure that no threads are about to start or
121 // exit. It is released again in SafepointSynchronize::end().
122 Threads_lock->lock();
123
124 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
125
126 int nof_threads = Threads::number_of_threads();
127
128 if (TraceSafepoint) {
129 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
130 }
131
132 RuntimeService::record_safepoint_begin();
133
134 MutexLocker mu(Safepoint_lock);
135
136 // Reset the count of active JNI critical threads
137 _current_jni_active_count = 0;
138
139 // Set number of threads to wait for, before we initiate the callbacks
140 _waiting_to_block = nof_threads;
141 TryingToBlock = 0 ;
142 int still_running = nof_threads;
143
144 // Save the starting time, so that it can be compared to see if this has taken
145 // too long to complete.
146 jlong safepoint_limit_time;
147 timeout_error_printed = false;
148
149 // PrintSafepointStatisticsTimeout can be specified separately. When
150 // specified, PrintSafepointStatistics will be set to true in
151 // deferred_initialize_stat method. The initialization has to be done
152 // early enough to avoid any races. See bug 6880029 for details.
153 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
154 deferred_initialize_stat();
155 }
156
157 // Begin the process of bringing the system to a safepoint.
158 // Java threads can be in several different states and are
159 // stopped by different mechanisms:
160 //
161 // 1. Running interpreted
162 // The interpreter dispatch table is changed to force it to
163 // check for a safepoint condition between bytecodes.
164 // 2. Running in native code
165 // When returning from the native code, a Java thread must check
166 // the safepoint _state to see if we must block. If the
167 // VM thread sees a Java thread in native, it does
168 // not wait for this thread to block. The order of the memory
169 // writes and reads of both the safepoint state and the Java
170 // threads state is critical. In order to guarantee that the
171 // memory writes are serialized with respect to each other,
172 // the VM thread issues a memory barrier instruction
173 // (on MP systems). In order to avoid the overhead of issuing
174 // a memory barrier for each Java thread making native calls, each Java
175 // thread performs a write to a single memory page after changing
176 // the thread state. The VM thread performs a sequence of
177 // mprotect OS calls which forces all previous writes from all
178 // Java threads to be serialized. This is done in the
179 // os::serialize_thread_states() call. This has proven to be
180 // much more efficient than executing a membar instruction
181 // on every call to native code.
182 // 3. Running compiled Code
183 // Compiled code reads a global (Safepoint Polling) page that
184 // is set to fault if we are trying to get to a safepoint.
185 // 4. Blocked
186 // A thread which is blocked will not be allowed to return from the
187 // block condition until the safepoint operation is complete.
188 // 5. In VM or Transitioning between states
189 // If a Java thread is currently running in the VM or transitioning
190 // between states, the safepointing code will wait for the thread to
191 // block itself when it attempts transitions to a new state.
192 //
193 _state = _synchronizing;
194 OrderAccess::fence();
195
196 // Flush all thread states to memory
197 if (!UseMembar) {
198 os::serialize_thread_states();
199 }
200
201 // Make interpreter safepoint aware
202 Interpreter::notice_safepoints();
203
204 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
205 // Make polling safepoint aware
206 guarantee (PageArmed == 0, "invariant") ;
207 PageArmed = 1 ;
208 os::make_polling_page_unreadable();
209 }
210
211 // Consider using active_processor_count() ... but that call is expensive.
212 int ncpus = os::processor_count() ;
213
214 #ifdef ASSERT
215 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
216 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
217 // Clear the visited flag to ensure that the critical counts are collected properly.
218 cur->set_visited_for_critical_count(false);
219 }
220 #endif // ASSERT
221
222 if (SafepointTimeout)
223 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
224
225 // Iterate through all threads until it have been determined how to stop them all at a safepoint
226 unsigned int iterations = 0;
227 int steps = 0 ;
228 while(still_running > 0) {
229 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
230 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
231 ThreadSafepointState *cur_state = cur->safepoint_state();
232 if (cur_state->is_running()) {
233 cur_state->examine_state_of_thread();
234 if (!cur_state->is_running()) {
235 still_running--;
236 // consider adjusting steps downward:
237 // steps = 0
238 // steps -= NNN
239 // steps >>= 1
240 // steps = MIN(steps, 2000-100)
241 // if (iterations != 0) steps -= NNN
242 }
243 if (TraceSafepoint && Verbose) cur_state->print();
244 }
245 }
246
247 if (PrintSafepointStatistics && iterations == 0) {
248 begin_statistics(nof_threads, still_running);
249 }
250
251 if (still_running > 0) {
252 // Check for if it takes to long
253 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
254 print_safepoint_timeout(_spinning_timeout);
255 }
256
257 // Spin to avoid context switching.
258 // There's a tension between allowing the mutators to run (and rendezvous)
259 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
260 // a mutator might otherwise use profitably to reach a safepoint. Excessive
261 // spinning by the VM thread on a saturated system can increase rendezvous latency.
262 // Blocking or yielding incur their own penalties in the form of context switching
263 // and the resultant loss of $ residency.
264 //
265 // Further complicating matters is that yield() does not work as naively expected
266 // on many platforms -- yield() does not guarantee that any other ready threads
267 // will run. As such we revert to naked_short_sleep() after some number of iterations.
268 // nakes_short_sleep() is implemented as a short unconditional sleep.
269 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
270 // can actually increase the time it takes the VM thread to detect that a system-wide
271 // stop-the-world safepoint has been reached. In a pathological scenario such as that
272 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
273 // In that case the mutators will be stalled waiting for the safepoint to complete and the
274 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
275 // will eventually wake up and detect that all mutators are safe, at which point
276 // we'll again make progress.
277 //
278 // Beware too that that the VMThread typically runs at elevated priority.
279 // Its default priority is higher than the default mutator priority.
280 // Obviously, this complicates spinning.
281 //
282 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
283 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
284 //
285 // See the comments in synchronizer.cpp for additional remarks on spinning.
286 //
287 // In the future we might:
288 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
289 // This is tricky as the path used by a thread exiting the JVM (say on
290 // on JNI call-out) simply stores into its state field. The burden
291 // is placed on the VM thread, which must poll (spin).
292 // 2. Find something useful to do while spinning. If the safepoint is GC-related
293 // we might aggressively scan the stacks of threads that are already safe.
294 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
295 // If all the mutators are ONPROC there's no reason to sleep or yield.
296 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
297 // 5. Check system saturation. If the system is not fully saturated then
298 // simply spin and avoid sleep/yield.
299 // 6. As still-running mutators rendezvous they could unpark the sleeping
300 // VMthread. This works well for still-running mutators that become
301 // safe. The VMthread must still poll for mutators that call-out.
302 // 7. Drive the policy on time-since-begin instead of iterations.
303 // 8. Consider making the spin duration a function of the # of CPUs:
304 // Spin = (((ncpus-1) * M) + K) + F(still_running)
305 // Alternately, instead of counting iterations of the outer loop
306 // we could count the # of threads visited in the inner loop, above.
307 // 9. On windows consider using the return value from SwitchThreadTo()
308 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
309
310 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
311 guarantee (PageArmed == 0, "invariant") ;
312 PageArmed = 1 ;
313 os::make_polling_page_unreadable();
314 }
315
316 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
317 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
318 ++steps ;
319 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
320 SpinPause() ; // MP-Polite spin
321 } else
322 if (steps < DeferThrSuspendLoopCount) {
323 os::NakedYield() ;
324 } else {
325 os::naked_short_sleep(1);
326 }
327
328 iterations ++ ;
329 }
330 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
331 }
332 assert(still_running == 0, "sanity check");
333
334 if (PrintSafepointStatistics) {
335 update_statistics_on_spin_end();
336 }
337
338 // wait until all threads are stopped
339 while (_waiting_to_block > 0) {
340 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
341 if (!SafepointTimeout || timeout_error_printed) {
342 Safepoint_lock->wait(true); // true, means with no safepoint checks
343 } else {
344 // Compute remaining time
345 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
346
347 // If there is no remaining time, then there is an error
348 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
349 print_safepoint_timeout(_blocking_timeout);
350 }
351 }
352 }
353 assert(_waiting_to_block == 0, "sanity check");
354
355 #ifndef PRODUCT
356 if (SafepointTimeout) {
357 jlong current_time = os::javaTimeNanos();
358 if (safepoint_limit_time < current_time) {
359 tty->print_cr("# SafepointSynchronize: Finished after "
360 INT64_FORMAT_W(6) " ms",
361 ((current_time - safepoint_limit_time) / MICROUNITS +
362 SafepointTimeoutDelay));
363 }
364 }
365 #endif
366
367 assert((_safepoint_counter & 0x1) == 0, "must be even");
368 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
369 _safepoint_counter ++;
370
371 // Record state
372 _state = _synchronized;
373
374 OrderAccess::fence();
375
376 #ifdef ASSERT
377 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
378 // make sure all the threads were visited
379 assert(cur->was_visited_for_critical_count(), "missed a thread");
380 }
381 #endif // ASSERT
382
383 // Update the count of active JNI critical regions
384 GC_locker::set_jni_lock_count(_current_jni_active_count);
385
386 if (TraceSafepoint) {
387 VM_Operation *op = VMThread::vm_operation();
388 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
389 }
390
391 RuntimeService::record_safepoint_synchronized();
392 if (PrintSafepointStatistics) {
393 update_statistics_on_sync_end(os::javaTimeNanos());
394 }
395
396 // Call stuff that needs to be run when a safepoint is just about to be completed
397 do_cleanup_tasks();
398
399 if (PrintSafepointStatistics) {
400 // Record how much time spend on the above cleanup tasks
401 update_statistics_on_cleanup_end(os::javaTimeNanos());
402 }
403 }
404
405 // Wake up all threads, so they are ready to resume execution after the safepoint
406 // operation has been carried out
407 void SafepointSynchronize::end() {
408
409 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
410 assert((_safepoint_counter & 0x1) == 1, "must be odd");
411 _safepoint_counter ++;
412 // memory fence isn't required here since an odd _safepoint_counter
413 // value can do no harm and a fence is issued below anyway.
414
415 DEBUG_ONLY(Thread* myThread = Thread::current();)
416 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
417
418 if (PrintSafepointStatistics) {
419 end_statistics(os::javaTimeNanos());
420 }
421
422 #ifdef ASSERT
423 // A pending_exception cannot be installed during a safepoint. The threads
424 // may install an async exception after they come back from a safepoint into
425 // pending_exception after they unblock. But that should happen later.
426 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
427 assert (!(cur->has_pending_exception() &&
428 cur->safepoint_state()->is_at_poll_safepoint()),
429 "safepoint installed a pending exception");
430 }
431 #endif // ASSERT
432
433 if (PageArmed) {
434 // Make polling safepoint aware
435 os::make_polling_page_readable();
436 PageArmed = 0 ;
437 }
438
439 // Remove safepoint check from interpreter
440 Interpreter::ignore_safepoints();
441
442 {
443 MutexLocker mu(Safepoint_lock);
444
445 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
446
447 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
448 // when they get restarted.
449 _state = _not_synchronized;
450 OrderAccess::fence();
451
452 if (TraceSafepoint) {
453 tty->print_cr("Leaving safepoint region");
454 }
455
456 // Start suspended threads
457 for(JavaThread *current = Threads::first(); current; current = current->next()) {
458 // A problem occurring on Solaris is when attempting to restart threads
459 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
460 // to the next one (since it has been running the longest). We then have
461 // to wait for a cpu to become available before we can continue restarting
462 // threads.
463 // FIXME: This causes the performance of the VM to degrade when active and with
464 // large numbers of threads. Apparently this is due to the synchronous nature
465 // of suspending threads.
466 //
467 // TODO-FIXME: the comments above are vestigial and no longer apply.
468 // Furthermore, using solaris' schedctl in this particular context confers no benefit
469 if (VMThreadHintNoPreempt) {
470 os::hint_no_preempt();
471 }
472 ThreadSafepointState* cur_state = current->safepoint_state();
473 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
474 cur_state->restart();
475 assert(cur_state->is_running(), "safepoint state has not been reset");
476 }
477
478 RuntimeService::record_safepoint_end();
479
480 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
481 // blocked in signal_thread_blocked
482 Threads_lock->unlock();
483
484 }
485 #if INCLUDE_ALL_GCS
486 // If there are any concurrent GC threads resume them.
487 if (UseConcMarkSweepGC) {
488 ConcurrentMarkSweepThread::desynchronize(false);
489 } else if (UseG1GC) {
490 SuspendibleThreadSet::desynchronize();
491 }
492 #endif // INCLUDE_ALL_GCS
493 // record this time so VMThread can keep track how much time has elapsed
494 // since last safepoint.
495 _end_of_last_safepoint = os::javaTimeMillis();
496 }
497
498 bool SafepointSynchronize::is_cleanup_needed() {
499 // Need a safepoint if some inline cache buffers is non-empty
500 if (!InlineCacheBuffer::is_empty()) return true;
501 return false;
502 }
503
504
505
506 // Various cleaning tasks that should be done periodically at safepoints
507 void SafepointSynchronize::do_cleanup_tasks() {
508 {
509 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime);
510 ObjectSynchronizer::deflate_idle_monitors();
511 }
512
513 {
514 TraceTime t2("updating inline caches", TraceSafepointCleanupTime);
515 InlineCacheBuffer::update_inline_caches();
516 }
517 {
518 TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime);
519 CompilationPolicy::policy()->do_safepoint_work();
520 }
521
522 {
523 TraceTime t4("mark nmethods", TraceSafepointCleanupTime);
524 NMethodSweeper::mark_active_nmethods();
525 }
526
527 if (SymbolTable::needs_rehashing()) {
528 TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime);
529 SymbolTable::rehash_table();
530 }
531
532 if (StringTable::needs_rehashing()) {
533 TraceTime t6("rehashing string table", TraceSafepointCleanupTime);
534 StringTable::rehash_table();
535 }
536
537 // rotate log files?
538 if (UseGCLogFileRotation) {
539 gclog_or_tty->rotate_log(false);
540 }
541
542 {
543 // CMS delays purging the CLDG until the beginning of the next safepoint and to
544 // make sure concurrent sweep is done
545 TraceTime t7("purging class loader data graph", TraceSafepointCleanupTime);
546 ClassLoaderDataGraph::purge_if_needed();
547 }
548
549 if (MemTracker::is_on()) {
550 MemTracker::sync();
551 }
552 }
553
554
555 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
556 switch(state) {
557 case _thread_in_native:
558 // native threads are safe if they have no java stack or have walkable stack
559 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
560
561 // blocked threads should have already have walkable stack
562 case _thread_blocked:
563 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
564 return true;
565
566 default:
567 return false;
568 }
569 }
570
571
572 // See if the thread is running inside a lazy critical native and
573 // update the thread critical count if so. Also set a suspend flag to
574 // cause the native wrapper to return into the JVM to do the unlock
575 // once the native finishes.
576 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
577 if (state == _thread_in_native &&
578 thread->has_last_Java_frame() &&
579 thread->frame_anchor()->walkable()) {
580 // This thread might be in a critical native nmethod so look at
581 // the top of the stack and increment the critical count if it
582 // is.
583 frame wrapper_frame = thread->last_frame();
584 CodeBlob* stub_cb = wrapper_frame.cb();
585 if (stub_cb != NULL &&
586 stub_cb->is_nmethod() &&
587 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
588 // A thread could potentially be in a critical native across
589 // more than one safepoint, so only update the critical state on
590 // the first one. When it returns it will perform the unlock.
591 if (!thread->do_critical_native_unlock()) {
592 #ifdef ASSERT
593 if (!thread->in_critical()) {
594 GC_locker::increment_debug_jni_lock_count();
595 }
596 #endif
597 thread->enter_critical();
598 // Make sure the native wrapper calls back on return to
599 // perform the needed critical unlock.
600 thread->set_critical_native_unlock();
601 }
602 }
603 }
604 }
605
606
607
608 // -------------------------------------------------------------------------------------------------------
609 // Implementation of Safepoint callback point
610
611 void SafepointSynchronize::block(JavaThread *thread) {
612 assert(thread != NULL, "thread must be set");
613 assert(thread->is_Java_thread(), "not a Java thread");
614
615 // Threads shouldn't block if they are in the middle of printing, but...
616 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
617
618 // Only bail from the block() call if the thread is gone from the
619 // thread list; starting to exit should still block.
620 if (thread->is_terminated()) {
621 // block current thread if we come here from native code when VM is gone
622 thread->block_if_vm_exited();
623
624 // otherwise do nothing
625 return;
626 }
627
628 JavaThreadState state = thread->thread_state();
629 thread->frame_anchor()->make_walkable(thread);
630
631 // Check that we have a valid thread_state at this point
632 switch(state) {
633 case _thread_in_vm_trans:
634 case _thread_in_Java: // From compiled code
635
636 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
637 // we pretend we are still in the VM.
638 thread->set_thread_state(_thread_in_vm);
639
640 if (is_synchronizing()) {
641 Atomic::inc (&TryingToBlock) ;
642 }
643
644 // We will always be holding the Safepoint_lock when we are examine the state
645 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
646 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
647 Safepoint_lock->lock_without_safepoint_check();
648 if (is_synchronizing()) {
649 // Decrement the number of threads to wait for and signal vm thread
650 assert(_waiting_to_block > 0, "sanity check");
651 _waiting_to_block--;
652 thread->safepoint_state()->set_has_called_back(true);
653
654 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
655 if (thread->in_critical()) {
656 // Notice that this thread is in a critical section
657 increment_jni_active_count();
658 }
659
660 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
661 if (_waiting_to_block == 0) {
662 Safepoint_lock->notify_all();
663 }
664 }
665
666 // We transition the thread to state _thread_blocked here, but
667 // we can't do our usual check for external suspension and then
668 // self-suspend after the lock_without_safepoint_check() call
669 // below because we are often called during transitions while
670 // we hold different locks. That would leave us suspended while
671 // holding a resource which results in deadlocks.
672 thread->set_thread_state(_thread_blocked);
673 Safepoint_lock->unlock();
674
675 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
676 // the entire safepoint, the threads will all line up here during the safepoint.
677 Threads_lock->lock_without_safepoint_check();
678 // restore original state. This is important if the thread comes from compiled code, so it
679 // will continue to execute with the _thread_in_Java state.
680 thread->set_thread_state(state);
681 Threads_lock->unlock();
682 break;
683
684 case _thread_in_native_trans:
685 case _thread_blocked_trans:
686 case _thread_new_trans:
687 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
688 thread->print_thread_state();
689 fatal("Deadlock in safepoint code. "
690 "Should have called back to the VM before blocking.");
691 }
692
693 // We transition the thread to state _thread_blocked here, but
694 // we can't do our usual check for external suspension and then
695 // self-suspend after the lock_without_safepoint_check() call
696 // below because we are often called during transitions while
697 // we hold different locks. That would leave us suspended while
698 // holding a resource which results in deadlocks.
699 thread->set_thread_state(_thread_blocked);
700
701 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
702 // the safepoint code might still be waiting for it to block. We need to change the state here,
703 // so it can see that it is at a safepoint.
704
705 // Block until the safepoint operation is completed.
706 Threads_lock->lock_without_safepoint_check();
707
708 // Restore state
709 thread->set_thread_state(state);
710
711 Threads_lock->unlock();
712 break;
713
714 default:
715 fatal(err_msg("Illegal threadstate encountered: %d", state));
716 }
717
718 // Check for pending. async. exceptions or suspends - except if the
719 // thread was blocked inside the VM. has_special_runtime_exit_condition()
720 // is called last since it grabs a lock and we only want to do that when
721 // we must.
722 //
723 // Note: we never deliver an async exception at a polling point as the
724 // compiler may not have an exception handler for it. The polling
725 // code will notice the async and deoptimize and the exception will
726 // be delivered. (Polling at a return point is ok though). Sure is
727 // a lot of bother for a deprecated feature...
728 //
729 // We don't deliver an async exception if the thread state is
730 // _thread_in_native_trans so JNI functions won't be called with
731 // a surprising pending exception. If the thread state is going back to java,
732 // async exception is checked in check_special_condition_for_native_trans().
733
734 if (state != _thread_blocked_trans &&
735 state != _thread_in_vm_trans &&
736 thread->has_special_runtime_exit_condition()) {
737 thread->handle_special_runtime_exit_condition(
738 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
739 }
740 }
741
742 // ------------------------------------------------------------------------------------------------------
743 // Exception handlers
744
745 #ifndef PRODUCT
746
747 #ifdef SPARC
748
749 #ifdef _LP64
750 #define PTR_PAD ""
751 #else
752 #define PTR_PAD " "
753 #endif
754
755 static void print_ptrs(intptr_t oldptr, intptr_t newptr, bool wasoop) {
756 bool is_oop = newptr ? (cast_to_oop(newptr))->is_oop() : false;
757 tty->print_cr(PTR_FORMAT PTR_PAD " %s %c " PTR_FORMAT PTR_PAD " %s %s",
758 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!',
759 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" "));
760 }
761
762 static void print_longs(jlong oldptr, jlong newptr, bool wasoop) {
763 bool is_oop = newptr ? (cast_to_oop(newptr))->is_oop() : false;
764 tty->print_cr(PTR64_FORMAT " %s %c " PTR64_FORMAT " %s %s",
765 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!',
766 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" "));
767 }
768
769 static void print_me(intptr_t *new_sp, intptr_t *old_sp, bool *was_oops) {
770 #ifdef _LP64
771 tty->print_cr("--------+------address-----+------before-----------+-------after----------+");
772 const int incr = 1; // Increment to skip a long, in units of intptr_t
773 #else
774 tty->print_cr("--------+--address-+------before-----------+-------after----------+");
775 const int incr = 2; // Increment to skip a long, in units of intptr_t
776 #endif
777 tty->print_cr("---SP---|");
778 for( int i=0; i<16; i++ ) {
779 tty->print("blob %c%d |"PTR_FORMAT" ","LO"[i>>3],i&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
780 tty->print_cr("--------|");
781 for( int i1=0; i1<frame::memory_parameter_word_sp_offset-16; i1++ ) {
782 tty->print("argv pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
783 tty->print(" pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++);
784 tty->print_cr("--------|");
785 tty->print(" G1 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr;
786 tty->print(" G3 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr;
787 tty->print(" G4 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr;
788 tty->print(" G5 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr;
789 tty->print_cr(" FSR |"PTR_FORMAT" "PTR64_FORMAT" "PTR64_FORMAT,new_sp,*(jlong*)old_sp,*(jlong*)new_sp);
790 old_sp += incr; new_sp += incr; was_oops += incr;
791 // Skip the floats
792 tty->print_cr("--Float-|"PTR_FORMAT,new_sp);
793 tty->print_cr("---FP---|");
794 old_sp += incr*32; new_sp += incr*32; was_oops += incr*32;
795 for( int i2=0; i2<16; i2++ ) {
796 tty->print("call %c%d |"PTR_FORMAT" ","LI"[i2>>3],i2&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
797 tty->cr();
798 }
799 #endif // SPARC
800 #endif // PRODUCT
801
802
803 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
804 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
805 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
806 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
807
808 // Uncomment this to get some serious before/after printing of the
809 // Sparc safepoint-blob frame structure.
810 /*
811 intptr_t* sp = thread->last_Java_sp();
812 intptr_t stack_copy[150];
813 for( int i=0; i<150; i++ ) stack_copy[i] = sp[i];
814 bool was_oops[150];
815 for( int i=0; i<150; i++ )
816 was_oops[i] = stack_copy[i] ? ((oop)stack_copy[i])->is_oop() : false;
817 */
818
819 if (ShowSafepointMsgs) {
820 tty->print("handle_polling_page_exception: ");
821 }
822
823 if (PrintSafepointStatistics) {
824 inc_page_trap_count();
825 }
826
827 ThreadSafepointState* state = thread->safepoint_state();
828
829 state->handle_polling_page_exception();
830 // print_me(sp,stack_copy,was_oops);
831 }
832
833
834 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
835 if (!timeout_error_printed) {
836 timeout_error_printed = true;
837 // Print out the thread info which didn't reach the safepoint for debugging
838 // purposes (useful when there are lots of threads in the debugger).
839 tty->cr();
840 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
841 if (reason == _spinning_timeout) {
842 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
843 } else if (reason == _blocking_timeout) {
844 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
845 }
846
847 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
848 ThreadSafepointState *cur_state;
849 ResourceMark rm;
850 for(JavaThread *cur_thread = Threads::first(); cur_thread;
851 cur_thread = cur_thread->next()) {
852 cur_state = cur_thread->safepoint_state();
853
854 if (cur_thread->thread_state() != _thread_blocked &&
855 ((reason == _spinning_timeout && cur_state->is_running()) ||
856 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
857 tty->print("# ");
858 cur_thread->print();
859 tty->cr();
860 }
861 }
862 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
863 }
864
865 // To debug the long safepoint, specify both DieOnSafepointTimeout &
866 // ShowMessageBoxOnError.
867 if (DieOnSafepointTimeout) {
868 char msg[1024];
869 VM_Operation *op = VMThread::vm_operation();
870 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
871 SafepointTimeoutDelay,
872 op != NULL ? op->name() : "no vm operation");
873 fatal(msg);
874 }
875 }
876
877
878 // -------------------------------------------------------------------------------------------------------
879 // Implementation of ThreadSafepointState
880
881 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
882 _thread = thread;
883 _type = _running;
884 _has_called_back = false;
885 _at_poll_safepoint = false;
886 }
887
888 void ThreadSafepointState::create(JavaThread *thread) {
889 ThreadSafepointState *state = new ThreadSafepointState(thread);
890 thread->set_safepoint_state(state);
891 }
892
893 void ThreadSafepointState::destroy(JavaThread *thread) {
894 if (thread->safepoint_state()) {
895 delete(thread->safepoint_state());
896 thread->set_safepoint_state(NULL);
897 }
898 }
899
900 void ThreadSafepointState::examine_state_of_thread() {
901 assert(is_running(), "better be running or just have hit safepoint poll");
902
903 JavaThreadState state = _thread->thread_state();
904
905 // Save the state at the start of safepoint processing.
906 _orig_thread_state = state;
907
908 // Check for a thread that is suspended. Note that thread resume tries
909 // to grab the Threads_lock which we own here, so a thread cannot be
910 // resumed during safepoint synchronization.
911
912 // We check to see if this thread is suspended without locking to
913 // avoid deadlocking with a third thread that is waiting for this
914 // thread to be suspended. The third thread can notice the safepoint
915 // that we're trying to start at the beginning of its SR_lock->wait()
916 // call. If that happens, then the third thread will block on the
917 // safepoint while still holding the underlying SR_lock. We won't be
918 // able to get the SR_lock and we'll deadlock.
919 //
920 // We don't need to grab the SR_lock here for two reasons:
921 // 1) The suspend flags are both volatile and are set with an
922 // Atomic::cmpxchg() call so we should see the suspended
923 // state right away.
924 // 2) We're being called from the safepoint polling loop; if
925 // we don't see the suspended state on this iteration, then
926 // we'll come around again.
927 //
928 bool is_suspended = _thread->is_ext_suspended();
929 if (is_suspended) {
930 roll_forward(_at_safepoint);
931 return;
932 }
933
934 // Some JavaThread states have an initial safepoint state of
935 // running, but are actually at a safepoint. We will happily
936 // agree and update the safepoint state here.
937 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
938 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
939 roll_forward(_at_safepoint);
940 return;
941 }
942
943 if (state == _thread_in_vm) {
944 roll_forward(_call_back);
945 return;
946 }
947
948 // All other thread states will continue to run until they
949 // transition and self-block in state _blocked
950 // Safepoint polling in compiled code causes the Java threads to do the same.
951 // Note: new threads may require a malloc so they must be allowed to finish
952
953 assert(is_running(), "examine_state_of_thread on non-running thread");
954 return;
955 }
956
957 // Returns true is thread could not be rolled forward at present position.
958 void ThreadSafepointState::roll_forward(suspend_type type) {
959 _type = type;
960
961 switch(_type) {
962 case _at_safepoint:
963 SafepointSynchronize::signal_thread_at_safepoint();
964 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
965 if (_thread->in_critical()) {
966 // Notice that this thread is in a critical section
967 SafepointSynchronize::increment_jni_active_count();
968 }
969 break;
970
971 case _call_back:
972 set_has_called_back(false);
973 break;
974
975 case _running:
976 default:
977 ShouldNotReachHere();
978 }
979 }
980
981 void ThreadSafepointState::restart() {
982 switch(type()) {
983 case _at_safepoint:
984 case _call_back:
985 break;
986
987 case _running:
988 default:
989 tty->print_cr("restart thread "INTPTR_FORMAT" with state %d",
990 _thread, _type);
991 _thread->print();
992 ShouldNotReachHere();
993 }
994 _type = _running;
995 set_has_called_back(false);
996 }
997
998
999 void ThreadSafepointState::print_on(outputStream *st) const {
1000 const char *s;
1001
1002 switch(_type) {
1003 case _running : s = "_running"; break;
1004 case _at_safepoint : s = "_at_safepoint"; break;
1005 case _call_back : s = "_call_back"; break;
1006 default:
1007 ShouldNotReachHere();
1008 }
1009
1010 st->print_cr("Thread: " INTPTR_FORMAT
1011 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1012 _thread, _thread->osthread()->thread_id(), s, _has_called_back,
1013 _at_poll_safepoint);
1014
1015 _thread->print_thread_state_on(st);
1016 }
1017
1018
1019 // ---------------------------------------------------------------------------------------------------------------------
1020
1021 // Block the thread at the safepoint poll or poll return.
1022 void ThreadSafepointState::handle_polling_page_exception() {
1023
1024 // Check state. block() will set thread state to thread_in_vm which will
1025 // cause the safepoint state _type to become _call_back.
1026 assert(type() == ThreadSafepointState::_running,
1027 "polling page exception on thread not running state");
1028
1029 // Step 1: Find the nmethod from the return address
1030 if (ShowSafepointMsgs && Verbose) {
1031 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
1032 }
1033 address real_return_addr = thread()->saved_exception_pc();
1034
1035 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1036 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
1037 nmethod* nm = (nmethod*)cb;
1038
1039 // Find frame of caller
1040 frame stub_fr = thread()->last_frame();
1041 CodeBlob* stub_cb = stub_fr.cb();
1042 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1043 RegisterMap map(thread(), true);
1044 frame caller_fr = stub_fr.sender(&map);
1045
1046 // Should only be poll_return or poll
1047 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1048
1049 // This is a poll immediately before a return. The exception handling code
1050 // has already had the effect of causing the return to occur, so the execution
1051 // will continue immediately after the call. In addition, the oopmap at the
1052 // return point does not mark the return value as an oop (if it is), so
1053 // it needs a handle here to be updated.
1054 if( nm->is_at_poll_return(real_return_addr) ) {
1055 // See if return type is an oop.
1056 bool return_oop = nm->method()->is_returning_oop();
1057 Handle return_value;
1058 if (return_oop) {
1059 // The oop result has been saved on the stack together with all
1060 // the other registers. In order to preserve it over GCs we need
1061 // to keep it in a handle.
1062 oop result = caller_fr.saved_oop_result(&map);
1063 assert(result == NULL || result->is_oop(), "must be oop");
1064 return_value = Handle(thread(), result);
1065 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1066 }
1067
1068 // Block the thread
1069 SafepointSynchronize::block(thread());
1070
1071 // restore oop result, if any
1072 if (return_oop) {
1073 caller_fr.set_saved_oop_result(&map, return_value());
1074 }
1075 }
1076
1077 // This is a safepoint poll. Verify the return address and block.
1078 else {
1079 set_at_poll_safepoint(true);
1080
1081 // verify the blob built the "return address" correctly
1082 assert(real_return_addr == caller_fr.pc(), "must match");
1083
1084 // Block the thread
1085 SafepointSynchronize::block(thread());
1086 set_at_poll_safepoint(false);
1087
1088 // If we have a pending async exception deoptimize the frame
1089 // as otherwise we may never deliver it.
1090 if (thread()->has_async_condition()) {
1091 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1092 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1093 }
1094
1095 // If an exception has been installed we must check for a pending deoptimization
1096 // Deoptimize frame if exception has been thrown.
1097
1098 if (thread()->has_pending_exception() ) {
1099 RegisterMap map(thread(), true);
1100 frame caller_fr = stub_fr.sender(&map);
1101 if (caller_fr.is_deoptimized_frame()) {
1102 // The exception patch will destroy registers that are still
1103 // live and will be needed during deoptimization. Defer the
1104 // Async exception should have deferred the exception until the
1105 // next safepoint which will be detected when we get into
1106 // the interpreter so if we have an exception now things
1107 // are messed up.
1108
1109 fatal("Exception installed and deoptimization is pending");
1110 }
1111 }
1112 }
1113 }
1114
1115
1116 //
1117 // Statistics & Instrumentations
1118 //
1119 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1120 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1121 int SafepointSynchronize::_cur_stat_index = 0;
1122 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1123 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1124 jlong SafepointSynchronize::_max_sync_time = 0;
1125 jlong SafepointSynchronize::_max_vmop_time = 0;
1126 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1127
1128 static jlong cleanup_end_time = 0;
1129 static bool need_to_track_page_armed_status = false;
1130 static bool init_done = false;
1131
1132 // Helper method to print the header.
1133 static void print_header() {
1134 tty->print(" vmop "
1135 "[threads: total initially_running wait_to_block] ");
1136 tty->print("[time: spin block sync cleanup vmop] ");
1137
1138 // no page armed status printed out if it is always armed.
1139 if (need_to_track_page_armed_status) {
1140 tty->print("page_armed ");
1141 }
1142
1143 tty->print_cr("page_trap_count");
1144 }
1145
1146 void SafepointSynchronize::deferred_initialize_stat() {
1147 if (init_done) return;
1148
1149 if (PrintSafepointStatisticsCount <= 0) {
1150 fatal("Wrong PrintSafepointStatisticsCount");
1151 }
1152
1153 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1154 // be printed right away, in which case, _safepoint_stats will regress to
1155 // a single element array. Otherwise, it is a circular ring buffer with default
1156 // size of PrintSafepointStatisticsCount.
1157 int stats_array_size;
1158 if (PrintSafepointStatisticsTimeout > 0) {
1159 stats_array_size = 1;
1160 PrintSafepointStatistics = true;
1161 } else {
1162 stats_array_size = PrintSafepointStatisticsCount;
1163 }
1164 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1165 * sizeof(SafepointStats), mtInternal);
1166 guarantee(_safepoint_stats != NULL,
1167 "not enough memory for safepoint instrumentation data");
1168
1169 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
1170 need_to_track_page_armed_status = true;
1171 }
1172 init_done = true;
1173 }
1174
1175 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1176 assert(init_done, "safepoint statistics array hasn't been initialized");
1177 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1178
1179 spstat->_time_stamp = _ts_of_current_safepoint;
1180
1181 VM_Operation *op = VMThread::vm_operation();
1182 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1183 if (op != NULL) {
1184 _safepoint_reasons[spstat->_vmop_type]++;
1185 }
1186
1187 spstat->_nof_total_threads = nof_threads;
1188 spstat->_nof_initial_running_threads = nof_running;
1189 spstat->_nof_threads_hit_page_trap = 0;
1190
1191 // Records the start time of spinning. The real time spent on spinning
1192 // will be adjusted when spin is done. Same trick is applied for time
1193 // spent on waiting for threads to block.
1194 if (nof_running != 0) {
1195 spstat->_time_to_spin = os::javaTimeNanos();
1196 } else {
1197 spstat->_time_to_spin = 0;
1198 }
1199 }
1200
1201 void SafepointSynchronize::update_statistics_on_spin_end() {
1202 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1203
1204 jlong cur_time = os::javaTimeNanos();
1205
1206 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1207 if (spstat->_nof_initial_running_threads != 0) {
1208 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1209 }
1210
1211 if (need_to_track_page_armed_status) {
1212 spstat->_page_armed = (PageArmed == 1);
1213 }
1214
1215 // Records the start time of waiting for to block. Updated when block is done.
1216 if (_waiting_to_block != 0) {
1217 spstat->_time_to_wait_to_block = cur_time;
1218 } else {
1219 spstat->_time_to_wait_to_block = 0;
1220 }
1221 }
1222
1223 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1224 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1225
1226 if (spstat->_nof_threads_wait_to_block != 0) {
1227 spstat->_time_to_wait_to_block = end_time -
1228 spstat->_time_to_wait_to_block;
1229 }
1230
1231 // Records the end time of sync which will be used to calculate the total
1232 // vm operation time. Again, the real time spending in syncing will be deducted
1233 // from the start of the sync time later when end_statistics is called.
1234 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1235 if (spstat->_time_to_sync > _max_sync_time) {
1236 _max_sync_time = spstat->_time_to_sync;
1237 }
1238
1239 spstat->_time_to_do_cleanups = end_time;
1240 }
1241
1242 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1243 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1244
1245 // Record how long spent in cleanup tasks.
1246 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1247
1248 cleanup_end_time = end_time;
1249 }
1250
1251 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1252 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1253
1254 // Update the vm operation time.
1255 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1256 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1257 _max_vmop_time = spstat->_time_to_exec_vmop;
1258 }
1259 // Only the sync time longer than the specified
1260 // PrintSafepointStatisticsTimeout will be printed out right away.
1261 // By default, it is -1 meaning all samples will be put into the list.
1262 if ( PrintSafepointStatisticsTimeout > 0) {
1263 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1264 print_statistics();
1265 }
1266 } else {
1267 // The safepoint statistics will be printed out when the _safepoin_stats
1268 // array fills up.
1269 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1270 print_statistics();
1271 _cur_stat_index = 0;
1272 } else {
1273 _cur_stat_index++;
1274 }
1275 }
1276 }
1277
1278 void SafepointSynchronize::print_statistics() {
1279 SafepointStats* sstats = _safepoint_stats;
1280
1281 for (int index = 0; index <= _cur_stat_index; index++) {
1282 if (index % 30 == 0) {
1283 print_header();
1284 }
1285 sstats = &_safepoint_stats[index];
1286 tty->print("%.3f: ", sstats->_time_stamp);
1287 tty->print("%-26s ["
1288 INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15)
1289 " ] ",
1290 sstats->_vmop_type == -1 ? "no vm operation" :
1291 VM_Operation::name(sstats->_vmop_type),
1292 sstats->_nof_total_threads,
1293 sstats->_nof_initial_running_threads,
1294 sstats->_nof_threads_wait_to_block);
1295 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1296 tty->print(" ["
1297 INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1298 INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1299 INT64_FORMAT_W(6)" ] ",
1300 sstats->_time_to_spin / MICROUNITS,
1301 sstats->_time_to_wait_to_block / MICROUNITS,
1302 sstats->_time_to_sync / MICROUNITS,
1303 sstats->_time_to_do_cleanups / MICROUNITS,
1304 sstats->_time_to_exec_vmop / MICROUNITS);
1305
1306 if (need_to_track_page_armed_status) {
1307 tty->print(INT32_FORMAT" ", sstats->_page_armed);
1308 }
1309 tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap);
1310 }
1311 }
1312
1313 // This method will be called when VM exits. It will first call
1314 // print_statistics to print out the rest of the sampling. Then
1315 // it tries to summarize the sampling.
1316 void SafepointSynchronize::print_stat_on_exit() {
1317 if (_safepoint_stats == NULL) return;
1318
1319 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1320
1321 // During VM exit, end_statistics may not get called and in that
1322 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1323 // don't print it out.
1324 // Approximate the vm op time.
1325 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1326 os::javaTimeNanos() - cleanup_end_time;
1327
1328 if ( PrintSafepointStatisticsTimeout < 0 ||
1329 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1330 print_statistics();
1331 }
1332 tty->cr();
1333
1334 // Print out polling page sampling status.
1335 if (!need_to_track_page_armed_status) {
1336 if (UseCompilerSafepoints) {
1337 tty->print_cr("Polling page always armed");
1338 }
1339 } else {
1340 tty->print_cr("Defer polling page loop count = %d\n",
1341 DeferPollingPageLoopCount);
1342 }
1343
1344 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1345 if (_safepoint_reasons[index] != 0) {
1346 tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index),
1347 _safepoint_reasons[index]);
1348 }
1349 }
1350
1351 tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint",
1352 _coalesced_vmop_count);
1353 tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms",
1354 _max_sync_time / MICROUNITS);
1355 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1356 INT64_FORMAT_W(5)" ms",
1357 _max_vmop_time / MICROUNITS);
1358 }
1359
1360 // ------------------------------------------------------------------------------------------------
1361 // Non-product code
1362
1363 #ifndef PRODUCT
1364
1365 void SafepointSynchronize::print_state() {
1366 if (_state == _not_synchronized) {
1367 tty->print_cr("not synchronized");
1368 } else if (_state == _synchronizing || _state == _synchronized) {
1369 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1370 "synchronized");
1371
1372 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1373 cur->safepoint_state()->print();
1374 }
1375 }
1376 }
1377
1378 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1379 if (ShowSafepointMsgs) {
1380 va_list ap;
1381 va_start(ap, format);
1382 tty->vprint_cr(format, ap);
1383 va_end(ap);
1384 }
1385 }
1386
1387 #endif // !PRODUCT