duke@435: /*
stefank@2314:  * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.
duke@435:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435:  *
duke@435:  * This code is free software; you can redistribute it and/or modify it
duke@435:  * under the terms of the GNU General Public License version 2 only, as
duke@435:  * published by the Free Software Foundation.
duke@435:  *
duke@435:  * This code is distributed in the hope that it will be useful, but WITHOUT
duke@435:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
duke@435:  * version 2 for more details (a copy is included in the LICENSE file that
duke@435:  * accompanied this code).
duke@435:  *
duke@435:  * You should have received a copy of the GNU General Public License version
duke@435:  * 2 along with this work; if not, write to the Free Software Foundation,
duke@435:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435:  *
trims@1907:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
trims@1907:  * or visit www.oracle.com if you need additional information or have any
trims@1907:  * questions.
duke@435:  *
duke@435:  */
duke@435: 
stefank@2314: #include "precompiled.hpp"
stefank@4299: #include "runtime/thread.inline.hpp"
stefank@2314: #include "runtime/threadCritical.hpp"
duke@435: 
duke@435: // OS-includes here
duke@435: # include <windows.h>
duke@435: # include <winbase.h>
duke@435: 
duke@435: //
duke@435: // See threadCritical.hpp for details of this class.
duke@435: //
duke@435: 
duke@435: static bool initialized = false;
duke@435: static volatile jint lock_count = -1;
duke@435: static HANDLE lock_event;
duke@435: static DWORD lock_owner = -1;
duke@435: 
duke@435: //
duke@435: // Note that Microsoft's critical region code contains a race
duke@435: // condition, and is not suitable for use. A thread holding the
duke@435: // critical section cannot safely suspend a thread attempting
duke@435: // to enter the critical region. The failure mode is that both
duke@435: // threads are permanently suspended.
duke@435: //
duke@435: // I experiemented with the use of ordinary windows mutex objects
duke@435: // and found them ~30 times slower than the critical region code.
duke@435: //
duke@435: 
duke@435: void ThreadCritical::initialize() {
duke@435: }
duke@435: 
duke@435: void ThreadCritical::release() {
duke@435:   assert(lock_owner == -1, "Mutex being deleted while owned.");
duke@435:   assert(lock_count == -1, "Mutex being deleted while recursively locked");
duke@435:   assert(lock_event != NULL, "Sanity check");
duke@435:   CloseHandle(lock_event);
duke@435: }
duke@435: 
duke@435: ThreadCritical::ThreadCritical() {
duke@435:   DWORD current_thread = GetCurrentThreadId();
duke@435: 
duke@435:   if (lock_owner != current_thread) {
duke@435:     // Grab the lock before doing anything.
duke@435:     while (Atomic::cmpxchg(0, &lock_count, -1) != -1) {
duke@435:       if (initialized) {
duke@435:         DWORD ret = WaitForSingleObject(lock_event,  INFINITE);
duke@435:         assert(ret == WAIT_OBJECT_0, "unexpected return value from WaitForSingleObject");
duke@435:       }
duke@435:     }
duke@435: 
duke@435:     // Make sure the event object is allocated.
duke@435:     if (!initialized) {
duke@435:       // Locking will not work correctly unless this is autoreset.
duke@435:       lock_event = CreateEvent(NULL, false, false, NULL);
duke@435:       initialized = true;
duke@435:     }
duke@435: 
duke@435:     assert(lock_owner == -1, "Lock acquired illegally.");
duke@435:     lock_owner = current_thread;
duke@435:   } else {
duke@435:     // Atomicity isn't required. Bump the recursion count.
duke@435:     lock_count++;
duke@435:   }
duke@435: 
duke@435:   assert(lock_owner == GetCurrentThreadId(), "Lock acquired illegally.");
duke@435: }
duke@435: 
duke@435: ThreadCritical::~ThreadCritical() {
duke@435:   assert(lock_owner == GetCurrentThreadId(), "unlock attempt by wrong thread");
duke@435:   assert(lock_count >= 0, "Attempt to unlock when already unlocked");
duke@435: 
duke@435:   if (lock_count == 0) {
duke@435:     // We're going to unlock
duke@435:     lock_owner = -1;
duke@435:     lock_count = -1;
duke@435:     // No lost wakeups, lock_event stays signaled until reset.
duke@435:     DWORD ret = SetEvent(lock_event);
duke@435:     assert(ret != 0, "unexpected return value from SetEvent");
duke@435:   } else {
duke@435:     // Just unwinding a recursive lock;
duke@435:     lock_count--;
duke@435:   }
duke@435: }