95 lines
3.5 KiB
C
95 lines
3.5 KiB
C
/* This file implements atomic counters using __atomic or __sync macros if
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* available, otherwise synchronizing different threads using a mutex.
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*
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* The exported interaface is composed of three macros:
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*
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* atomicIncr(var,count,mutex) -- Increment the atomic counter
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* atomicDecr(var,count,mutex) -- Decrement the atomic counter
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* atomicGet(var,dstvar,mutex) -- Fetch the atomic counter value
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*
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* If atomic primitives are available (tested in config.h) the mutex
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* is not used.
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*
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* Never use return value from the macros. To update and get use instead:
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*
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* atomicIncr(mycounter,...);
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* atomicGet(mycounter,newvalue);
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* doSomethingWith(newvalue);
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*
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* ----------------------------------------------------------------------------
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*
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* Copyright (c) 2015, Salvatore Sanfilippo <antirez at gmail dot com>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* * Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* * Neither the name of Redis nor the names of its contributors may be used
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* to endorse or promote products derived from this software without
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* specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <pthread.h>
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#ifndef __ATOMIC_VAR_H
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#define __ATOMIC_VAR_H
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#if defined(__ATOMIC_RELAXED)
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/* Implementation using __atomic macros. */
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#define atomicIncr(var,count,mutex) __atomic_add_fetch(&var,(count),__ATOMIC_RELAXED)
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#define atomicDecr(var,count,mutex) __atomic_sub_fetch(&var,(count),__ATOMIC_RELAXED)
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#define atomicGet(var,dstvar,mutex) do { \
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dstvar = __atomic_load_n(&var,__ATOMIC_RELAXED); \
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} while(0)
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#elif defined(HAVE_ATOMIC)
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/* Implementation using __sync macros. */
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#define atomicIncr(var,count,mutex) __sync_add_and_fetch(&var,(count))
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#define atomicDecr(var,count,mutex) __sync_sub_and_fetch(&var,(count))
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#define atomicGet(var,dstvar,mutex) do { \
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dstvar = __sync_sub_and_fetch(&var,0); \
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} while(0)
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#else
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/* Implementation using pthread mutex. */
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#define atomicIncr(var,count,mutex) do { \
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pthread_mutex_lock(&mutex); \
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var += (count); \
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pthread_mutex_unlock(&mutex); \
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} while(0)
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#define atomicDecr(var,count,mutex) do { \
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pthread_mutex_lock(&mutex); \
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var -= (count); \
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pthread_mutex_unlock(&mutex); \
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} while(0)
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#define atomicGet(var,dstvar,mutex) do { \
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pthread_mutex_lock(&mutex); \
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dstvar = var; \
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pthread_mutex_unlock(&mutex); \
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} while(0)
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#endif
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#endif /* __ATOMIC_VAR_H */
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