author | sangheki |
Wed, 13 Nov 2019 10:49:12 -0800 | |
changeset 59060 | fce1fa1bdc91 |
parent 47765 | b7c7428eaab9 |
child 59252 | 623722a6aeb9 |
permissions | -rw-r--r-- |
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/* |
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* Copyright (c) 2001, 2016, 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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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. |
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* |
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* This code is distributed in the hope that it will be useful, but WITHOUT |
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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* version 2 for more details (a copy is included in the LICENSE file that |
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* accompanied this code). |
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* |
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* You should have received a copy of the GNU General Public License version |
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* 2 along with this work; if not, write to the Free Software Foundation, |
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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* |
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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* or visit www.oracle.com if you need additional information or have any |
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* questions. |
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* |
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*/ |
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#include "precompiled.hpp" |
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#include "runtime/atomic.hpp" |
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#include "runtime/thread.inline.hpp" |
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#include "runtime/threadCritical.hpp" |
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// OS-includes here |
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# include <windows.h> |
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# include <winbase.h> |
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// |
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// See threadCritical.hpp for details of this class. |
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// |
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static bool initialized = false; |
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static volatile int lock_count = -1; |
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static HANDLE lock_event; |
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static DWORD lock_owner = -1; |
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// |
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// Note that Microsoft's critical region code contains a race |
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// condition, and is not suitable for use. A thread holding the |
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// critical section cannot safely suspend a thread attempting |
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// to enter the critical region. The failure mode is that both |
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// threads are permanently suspended. |
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// |
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// I experiemented with the use of ordinary windows mutex objects |
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// and found them ~30 times slower than the critical region code. |
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// |
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ThreadCritical::ThreadCritical() { |
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DWORD current_thread = GetCurrentThreadId(); |
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if (lock_owner != current_thread) { |
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// Grab the lock before doing anything. |
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while (Atomic::cmpxchg(0, &lock_count, -1) != -1) { |
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if (initialized) { |
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DWORD ret = WaitForSingleObject(lock_event, INFINITE); |
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assert(ret == WAIT_OBJECT_0, "unexpected return value from WaitForSingleObject"); |
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} |
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} |
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// Make sure the event object is allocated. |
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if (!initialized) { |
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// Locking will not work correctly unless this is autoreset. |
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lock_event = CreateEvent(NULL, false, false, NULL); |
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initialized = true; |
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} |
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assert(lock_owner == -1, "Lock acquired illegally."); |
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lock_owner = current_thread; |
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} else { |
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// Atomicity isn't required. Bump the recursion count. |
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lock_count++; |
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} |
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assert(lock_owner == GetCurrentThreadId(), "Lock acquired illegally."); |
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} |
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ThreadCritical::~ThreadCritical() { |
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assert(lock_owner == GetCurrentThreadId(), "unlock attempt by wrong thread"); |
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assert(lock_count >= 0, "Attempt to unlock when already unlocked"); |
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if (lock_count == 0) { |
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// We're going to unlock |
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lock_owner = -1; |
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lock_count = -1; |
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// No lost wakeups, lock_event stays signaled until reset. |
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DWORD ret = SetEvent(lock_event); |
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assert(ret != 0, "unexpected return value from SetEvent"); |
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} else { |
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// Just unwinding a recursive lock; |
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lock_count--; |
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} |
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} |