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/*
* Copyright (c) 2001, 2010, 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 "runtime/threadCritical.hpp"
#include "thread_windows.inline.hpp"
// OS-includes here
# include <windows.h>
# include <winbase.h>
//
// See threadCritical.hpp for details of this class.
//
static bool initialized = false;
static volatile jint lock_count = -1;
static HANDLE lock_event;
static DWORD lock_owner = -1;
//
// Note that Microsoft's critical region code contains a race
// condition, and is not suitable for use. A thread holding the
// critical section cannot safely suspend a thread attempting
// to enter the critical region. The failure mode is that both
// threads are permanently suspended.
//
// I experiemented with the use of ordinary windows mutex objects
// and found them ~30 times slower than the critical region code.
//
void ThreadCritical::initialize() {
}
void ThreadCritical::release() {
assert(lock_owner == -1, "Mutex being deleted while owned.");
assert(lock_count == -1, "Mutex being deleted while recursively locked");
assert(lock_event != NULL, "Sanity check");
CloseHandle(lock_event);
}
ThreadCritical::ThreadCritical() {
DWORD current_thread = GetCurrentThreadId();
if (lock_owner != current_thread) {
// Grab the lock before doing anything.
while (Atomic::cmpxchg(0, &lock_count, -1) != -1) {
if (initialized) {
DWORD ret = WaitForSingleObject(lock_event, INFINITE);
assert(ret == WAIT_OBJECT_0, "unexpected return value from WaitForSingleObject");
}
}
// Make sure the event object is allocated.
if (!initialized) {
// Locking will not work correctly unless this is autoreset.
lock_event = CreateEvent(NULL, false, false, NULL);
initialized = true;
}
assert(lock_owner == -1, "Lock acquired illegally.");
lock_owner = current_thread;
} else {
// Atomicity isn't required. Bump the recursion count.
lock_count++;
}
assert(lock_owner == GetCurrentThreadId(), "Lock acquired illegally.");
}
ThreadCritical::~ThreadCritical() {
assert(lock_owner == GetCurrentThreadId(), "unlock attempt by wrong thread");
assert(lock_count >= 0, "Attempt to unlock when already unlocked");
if (lock_count == 0) {
// We're going to unlock
lock_owner = -1;
lock_count = -1;
// No lost wakeups, lock_event stays signaled until reset.
DWORD ret = SetEvent(lock_event);
assert(ret != 0, "unexpected return value from SetEvent");
} else {
// Just unwinding a recursive lock;
lock_count--;
}
}
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