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/*
* Copyright (c) 2005, Eric Crahen
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is furnished
* to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
*/
#ifndef __ZTFASTLOCK_H__
#define __ZTFASTLOCK_H__
#include "zthread/NonCopyable.h"
#include "../ThreadOps.h"
#include <assert.h>
#include <asm/atomic.h>
#if !defined(NDEBUG)
# include <pthread.h>
#endif
namespace ZThread {
/**
* @class FastLock
*
* @author Eric Crahen <http://www.code-foo.com>
* @date <2003-07-16T23:27:03-0400>
* @version 2.2.0
*
* This implementation of a FastLock uses the atomic operations that
* linux provides with its kernel sources. This demonstrates how to implement
* a spinlock with a decrement and test primative.
*/
class FastLock : private NonCopyable {
atomic_t _value;
#if !defined(NDEBUG)
pthread_t _owner;
#endif
public:
inline FastLock() {
atomic_t tmp = ATOMIC_INIT(1);
_value = tmp;
}
inline ~FastLock() {
assert(atomic_read(&_value) == 1);
assert(_owner == 0);
}
inline void acquire() {
while(!atomic_dec_and_test(&_value)) {
atomic_inc(&_value);
ThreadOps::yield();
}
#if !defined(NDEBUG)
_owner = pthread_self();
#endif
}
inline void release() {
#if !defined(NDEBUG)
assert(pthread_equal(_owner, pthread_self()) != 0);
#endif
atomic_inc(&_value);
_owner = 0;
}
inline bool tryAcquire(unsigned long timeout=0) {
bool wasLocked = atomic_dec_and_test(&_value);
if(!wasLocked)
atomic_inc(&_value);
#if !defined(NDEBUG)
if(wasLocked)
_owner = pthread_self();
#endif
return wasLocked;
}
}; /* FastLock */
} // namespace ZThread
#endif
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