| /* |
| * Copyright (c) 2014, 2016, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| * |
| */ |
| |
| #include "precompiled.hpp" |
| #include "gc/g1/suspendibleThreadSet.hpp" |
| #include "runtime/mutexLocker.hpp" |
| #include "runtime/semaphore.hpp" |
| #include "runtime/thread.inline.hpp" |
| |
| uint SuspendibleThreadSet::_nthreads = 0; |
| uint SuspendibleThreadSet::_nthreads_stopped = 0; |
| bool SuspendibleThreadSet::_suspend_all = false; |
| double SuspendibleThreadSet::_suspend_all_start = 0.0; |
| |
| static Semaphore* _synchronize_wakeup = NULL; |
| |
| void SuspendibleThreadSet_init() { |
| assert(_synchronize_wakeup == NULL, "STS already initialized"); |
| _synchronize_wakeup = new Semaphore(); |
| } |
| |
| bool SuspendibleThreadSet::is_synchronized() { |
| assert_lock_strong(STS_lock); |
| assert(_nthreads_stopped <= _nthreads, "invariant"); |
| return _nthreads_stopped == _nthreads; |
| } |
| |
| void SuspendibleThreadSet::join() { |
| assert(!Thread::current()->is_suspendible_thread(), "Thread already joined"); |
| MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag); |
| while (_suspend_all) { |
| ml.wait(Mutex::_no_safepoint_check_flag); |
| } |
| _nthreads++; |
| DEBUG_ONLY(Thread::current()->set_suspendible_thread();) |
| } |
| |
| void SuspendibleThreadSet::leave() { |
| assert(Thread::current()->is_suspendible_thread(), "Thread not joined"); |
| MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag); |
| assert(_nthreads > 0, "Invalid"); |
| DEBUG_ONLY(Thread::current()->clear_suspendible_thread();) |
| _nthreads--; |
| if (_suspend_all && is_synchronized()) { |
| // This leave completes a request, so inform the requestor. |
| _synchronize_wakeup->signal(); |
| } |
| } |
| |
| void SuspendibleThreadSet::yield() { |
| assert(Thread::current()->is_suspendible_thread(), "Must have joined"); |
| MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag); |
| if (_suspend_all) { |
| _nthreads_stopped++; |
| if (is_synchronized()) { |
| if (ConcGCYieldTimeout > 0) { |
| double now = os::elapsedTime(); |
| guarantee((now - _suspend_all_start) * 1000.0 < (double)ConcGCYieldTimeout, "Long delay"); |
| } |
| // This yield completes the request, so inform the requestor. |
| _synchronize_wakeup->signal(); |
| } |
| while (_suspend_all) { |
| ml.wait(Mutex::_no_safepoint_check_flag); |
| } |
| assert(_nthreads_stopped > 0, "Invalid"); |
| _nthreads_stopped--; |
| } |
| } |
| |
| void SuspendibleThreadSet::synchronize() { |
| assert(Thread::current()->is_VM_thread(), "Must be the VM thread"); |
| if (ConcGCYieldTimeout > 0) { |
| _suspend_all_start = os::elapsedTime(); |
| } |
| { |
| MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag); |
| assert(!_suspend_all, "Only one at a time"); |
| _suspend_all = true; |
| if (is_synchronized()) { |
| return; |
| } |
| } // Release lock before semaphore wait. |
| |
| // Semaphore initial count is zero. To reach here, there must be at |
| // least one not yielded thread in the set, e.g. is_synchronized() |
| // was false before the lock was released. A thread in the set will |
| // signal the semaphore iff it is the last to yield or leave while |
| // there is an active suspend request. So there will be exactly one |
| // signal, which will increment the semaphore count to one, which |
| // will then be consumed by this wait, returning it to zero. No |
| // thread can exit yield or enter the set until desynchronize is |
| // called, so there are no further opportunities for the semaphore |
| // being signaled until we get back here again for some later |
| // synchronize call. Hence, there is no need to re-check for |
| // is_synchronized after the wait; it will always be true there. |
| _synchronize_wakeup->wait(); |
| |
| #ifdef ASSERT |
| MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag); |
| assert(_suspend_all, "STS not synchronizing"); |
| assert(is_synchronized(), "STS not synchronized"); |
| #endif |
| } |
| |
| void SuspendibleThreadSet::desynchronize() { |
| assert(Thread::current()->is_VM_thread(), "Must be the VM thread"); |
| MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag); |
| assert(_suspend_all, "STS not synchronizing"); |
| assert(is_synchronized(), "STS not synchronized"); |
| _suspend_all = false; |
| ml.notify_all(); |
| } |