8072439: fix for 8047720 may need more work
Cleanup PeriodTask_lock usage. Also reviewed by varming@gmail.com. Co-authored-by: Carsten Varming <varming@gmail.com> Reviewed-by: dholmes, dcubed, mgronlun, coleenp
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hotspot/src/share/vm/runtime
@ -1,5 +1,5 @@
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/*
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* Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
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* Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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@ -421,9 +421,11 @@ void before_exit(JavaThread * thread) {
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os::infinite_sleep();
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}
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// Terminate watcher thread - must before disenrolling any periodic task
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if (PeriodicTask::num_tasks() > 0)
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// Stop the WatcherThread. We do this before disenrolling various
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// PeriodicTasks to reduce the likelihood of races.
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if (PeriodicTask::num_tasks() > 0) {
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WatcherThread::stop();
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}
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// Print statistics gathered (profiling ...)
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if (Arguments::has_profile()) {
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@ -1,5 +1,5 @@
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/*
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* Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
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* Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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@ -47,6 +47,8 @@ void PeriodicTask::print_intervals() {
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#endif
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void PeriodicTask::real_time_tick(int delay_time) {
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assert(Thread::current()->is_Watcher_thread(), "must be WatcherThread");
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#ifndef PRODUCT
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if (ProfilerCheckIntervals) {
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_ticks++;
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@ -60,6 +62,8 @@ void PeriodicTask::real_time_tick(int delay_time) {
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#endif
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{
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// The WatcherThread does not participate in the safepoint protocol
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// for the PeriodicTask_lock because it is not a JavaThread.
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MutexLockerEx ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
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int orig_num_tasks = _num_tasks;
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@ -74,8 +78,7 @@ void PeriodicTask::real_time_tick(int delay_time) {
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}
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int PeriodicTask::time_to_wait() {
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MutexLockerEx ml(PeriodicTask_lock->owned_by_self() ?
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NULL : PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
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assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
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if (_num_tasks == 0) {
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return 0; // sleep until shutdown or a task is enrolled
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@ -98,14 +101,19 @@ PeriodicTask::PeriodicTask(size_t interval_time) :
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}
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PeriodicTask::~PeriodicTask() {
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// This PeriodicTask may have already been disenrolled by a call
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// to disenroll() before the PeriodicTask was deleted.
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disenroll();
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}
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/* enroll could be called from a JavaThread, so we have to check for
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* safepoint when taking the lock to avoid deadlocking */
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// enroll the current PeriodicTask
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void PeriodicTask::enroll() {
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MutexLockerEx ml(PeriodicTask_lock->owned_by_self() ?
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NULL : PeriodicTask_lock);
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// Follow normal safepoint aware lock enter protocol if the caller does
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// not already own the PeriodicTask_lock. Otherwise, we don't try to
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// enter it again because VM internal Mutexes do not support recursion.
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//
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MutexLockerEx ml(PeriodicTask_lock->owned_by_self() ? NULL
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: PeriodicTask_lock);
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if (_num_tasks == PeriodicTask::max_tasks) {
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fatal("Overflow in PeriodicTask table");
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@ -113,18 +121,21 @@ void PeriodicTask::enroll() {
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_tasks[_num_tasks++] = this;
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WatcherThread* thread = WatcherThread::watcher_thread();
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if (thread) {
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if (thread != NULL) {
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thread->unpark();
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} else {
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WatcherThread::start();
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}
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}
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/* disenroll could be called from a JavaThread, so we have to check for
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* safepoint when taking the lock to avoid deadlocking */
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// disenroll the current PeriodicTask
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void PeriodicTask::disenroll() {
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MutexLockerEx ml(PeriodicTask_lock->owned_by_self() ?
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NULL : PeriodicTask_lock);
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// Follow normal safepoint aware lock enter protocol if the caller does
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// not already own the PeriodicTask_lock. Otherwise, we don't try to
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// enter it again because VM internal Mutexes do not support recursion.
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//
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MutexLockerEx ml(PeriodicTask_lock->owned_by_self() ? NULL
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: PeriodicTask_lock);
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int index;
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for(index = 0; index < _num_tasks && _tasks[index] != this; index++)
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@ -1,5 +1,5 @@
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/*
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* Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved.
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* Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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@ -54,6 +54,7 @@ class PeriodicTask: public CHeapObj<mtInternal> {
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static int _num_tasks;
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static PeriodicTask* _tasks[PeriodicTask::max_tasks];
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// Can only be called by the WatcherThread
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static void real_time_tick(int delay_time);
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#ifndef PRODUCT
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@ -98,6 +99,7 @@ class PeriodicTask: public CHeapObj<mtInternal> {
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// Calculate when the next periodic task will fire.
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// Called by the WatcherThread's run method.
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// Requires the PeriodicTask_lock.
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static int time_to_wait();
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// The task to perform at each period
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@ -1197,8 +1197,15 @@ WatcherThread::WatcherThread() : Thread(), _crash_protection(NULL) {
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}
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int WatcherThread::sleep() const {
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// The WatcherThread does not participate in the safepoint protocol
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// for the PeriodicTask_lock because it is not a JavaThread.
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MutexLockerEx ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
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if (_should_terminate) {
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// check for termination before we do any housekeeping or wait
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return 0; // we did not sleep.
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}
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// remaining will be zero if there are no tasks,
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// causing the WatcherThread to sleep until a task is
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// enrolled
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@ -1211,8 +1218,9 @@ int WatcherThread::sleep() const {
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jlong time_before_loop = os::javaTimeNanos();
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for (;;) {
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bool timedout = PeriodicTask_lock->wait(Mutex::_no_safepoint_check_flag, remaining);
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while (true) {
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bool timedout = PeriodicTask_lock->wait(Mutex::_no_safepoint_check_flag,
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remaining);
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jlong now = os::javaTimeNanos();
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if (remaining == 0) {
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@ -1253,7 +1261,7 @@ void WatcherThread::run() {
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this->initialize_thread_local_storage();
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this->set_native_thread_name(this->name());
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this->set_active_handles(JNIHandleBlock::allocate_block());
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while (!_should_terminate) {
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while (true) {
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assert(watcher_thread() == Thread::current(), "thread consistency check");
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assert(watcher_thread() == this, "thread consistency check");
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@ -1289,6 +1297,11 @@ void WatcherThread::run() {
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}
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}
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if (_should_terminate) {
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// check for termination before posting the next tick
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break;
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}
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PeriodicTask::real_time_tick(time_waited);
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}
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@ -1319,27 +1332,19 @@ void WatcherThread::make_startable() {
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}
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void WatcherThread::stop() {
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// Get the PeriodicTask_lock if we can. If we cannot, then the
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// WatcherThread is using it and we don't want to block on that lock
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// here because that might cause a safepoint deadlock depending on
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// what the current WatcherThread tasks are doing.
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bool have_lock = PeriodicTask_lock->try_lock();
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{
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// Follow normal safepoint aware lock enter protocol since the
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// WatcherThread is stopped by another JavaThread.
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MutexLocker ml(PeriodicTask_lock);
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_should_terminate = true;
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_should_terminate = true;
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OrderAccess::fence(); // ensure WatcherThread sees update in main loop
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if (have_lock) {
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WatcherThread* watcher = watcher_thread();
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if (watcher != NULL) {
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// If we managed to get the lock, then we should unpark the
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// WatcherThread so that it can see we want it to stop.
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// unpark the WatcherThread so it can see that it should terminate
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watcher->unpark();
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}
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PeriodicTask_lock->unlock();
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}
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// it is ok to take late safepoints here, if needed
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MutexLocker mu(Terminator_lock);
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while (watcher_thread() != NULL) {
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@ -1359,9 +1364,7 @@ void WatcherThread::stop() {
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}
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void WatcherThread::unpark() {
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MutexLockerEx ml(PeriodicTask_lock->owned_by_self()
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? NULL
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: PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
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assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
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PeriodicTask_lock->notify();
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}
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@ -3558,8 +3561,8 @@ jint Threads::create_vm(JavaVMInitArgs* args, bool* canTryAgain) {
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}
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{
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MutexLockerEx ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
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// Make sure the watcher thread can be started by WatcherThread::start()
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MutexLocker ml(PeriodicTask_lock);
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// Make sure the WatcherThread can be started by WatcherThread::start()
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// or by dynamic enrollment.
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WatcherThread::make_startable();
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// Start up the WatcherThread if there are any periodic tasks
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@ -1,5 +1,5 @@
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/*
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* Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
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* Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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@ -701,7 +701,8 @@ class WatcherThread: public Thread {
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static WatcherThread* _watcher_thread;
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static bool _startable;
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volatile static bool _should_terminate; // updated without holding lock
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// volatile due to at least one lock-free read
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volatile static bool _should_terminate;
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os::WatcherThreadCrashProtection* _crash_protection;
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public:
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