Mercurial > hg > truffle
view agent/src/os/win32/Monitor.cpp @ 3917:eca1193ca245
4965777: GC changes to support use of discovered field for pending references
Summary: If and when the reference handler thread is able to use the discovered field to link reference objects in its pending list, so will GC. In that case, GC will scan through this field once a reference object has been placed on the pending list, but not scan that field before that stage, as the field is used by the concurrent GC thread to link discovered objects. When ReferenceHandleR thread does not use the discovered field for the purpose of linking the elements in the pending list, as would be the case in older JDKs, the JVM will fall back to the old behaviour of using the next field for that purpose.
Reviewed-by: jcoomes, mchung, stefank
author | ysr |
---|---|
date | Wed, 07 Sep 2011 13:55:42 -0700 |
parents | c18cbe5936b8 |
children |
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/* * Copyright (c) 2001, 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 <stdio.h> #include <assert.h> #include "Monitor.hpp" Monitor::Monitor() { _lock_count = -1; // No threads have entered the critical section _owner = NULL; _lock_event = CreateEvent(NULL, false, false, NULL); _wait_event = CreateEvent(NULL, true, false, NULL); _counter = 0; _tickets = 0; _waiters = 0; } Monitor::~Monitor() { assert(_owner == NULL); // Otherwise, owned monitor being deleted assert(_lock_count == -1); // Otherwise, monitor being deleted with non -1 lock count CloseHandle(_lock_event); CloseHandle(_wait_event); } void Monitor::lock() { if (InterlockedIncrement(&_lock_count) == 0) { // Success, we now own the lock } else { DWORD dwRet = WaitForSingleObject((HANDLE)_lock_event, INFINITE); assert(dwRet == WAIT_OBJECT_0); // Unexpected return value from WaitForSingleObject } assert(owner() == NULL); // Otherwise, lock count and owner are inconsistent setOwner(GetCurrentThread()); } void Monitor::unlock() { setOwner(NULL); if (InterlockedDecrement(&_lock_count) >= 0) { // Wake a waiting thread up DWORD dwRet = SetEvent(_lock_event); assert(dwRet != 0); // Unexpected return value from SetEvent } } bool Monitor::wait(long timeout) { assert(owner() != NULL); assert(owner() == GetCurrentThread()); // 0 means forever. Convert to Windows specific code. DWORD timeout_value = (timeout == 0) ? INFINITE : timeout; DWORD which; long c = _counter; bool retry = false; _waiters++; // Loop until condition variable is signaled. The event object is // set whenever the condition variable is signaled, and tickets will // reflect the number of threads which have been notified. The counter // field is used to make sure we don't respond to notifications that // have occurred *before* we started waiting, and is incremented each // time the condition variable is signaled. while (true) { // Leave critical region unlock(); // If this is a retry, let other low-priority threads have a chance // to run. Make sure that we sleep outside of the critical section. if (retry) { Sleep(1); } else { retry = true; } which = WaitForSingleObject(_wait_event, timeout_value); // Enter critical section lock(); if (_tickets != 0 && _counter != c) break; if (which == WAIT_TIMEOUT) { --_waiters; return true; } } _waiters--; // If this was the last thread to be notified, then we need to reset // the event object. if (--_tickets == 0) { ResetEvent(_wait_event); } return false; } // Notify a single thread waiting on this monitor bool Monitor::notify() { assert(ownedBySelf()); // Otherwise, notify on unknown thread if (_waiters > _tickets) { if (!SetEvent(_wait_event)) { return false; } _tickets++; _counter++; } return true; } // Notify all threads waiting on this monitor bool Monitor::notifyAll() { assert(ownedBySelf()); // Otherwise, notifyAll on unknown thread if (_waiters > 0) { if (!SetEvent(_wait_event)) { return false; } _tickets = _waiters; _counter++; } return true; } HANDLE Monitor::owner() { return _owner; } void Monitor::setOwner(HANDLE owner) { if (owner != NULL) { assert(_owner == NULL); // Setting owner thread of already owned monitor assert(owner == GetCurrentThread()); // Else should not be doing this } else { HANDLE oldOwner = _owner; assert(oldOwner != NULL); // Removing the owner thread of an unowned mutex assert(oldOwner == GetCurrentThread()); } _owner = owner; } bool Monitor::ownedBySelf() { return (_owner == GetCurrentThread()); }