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/* This file implements atomic counters using __atomic or __sync macros if
* available, otherwise synchronizing different threads using a mutex.
*
* The exported interface is composed of three macros:
*
* atomicIncr(var,count) -- Increment the atomic counter
* atomicGetIncr(var,oldvalue_var,count) -- Get and increment the atomic counter
* atomicDecr(var,count) -- Decrement the atomic counter
* atomicGet(var,dstvar) -- Fetch the atomic counter value
* atomicSet(var,value) -- Set the atomic counter value
*
* The variable 'var' should also have a declared mutex with the same
* name and the "_mutex" postfix, for instance:
*
* long myvar;
* pthread_mutex_t myvar_mutex;
* atomicSet(myvar,12345);
*
* If atomic primitives are available (tested in config.h) the mutex
* is not used.
*
* Never use return value from the macros, instead use the AtomicGetIncr()
* if you need to get the current value and increment it atomically, like
* in the followign example:
*
* long oldvalue;
* atomicGetIncr(myvar,oldvalue,1);
* doSomethingWith(oldvalue);
*
* ----------------------------------------------------------------------------
*
* Copyright (c) 2015, Salvatore Sanfilippo <antirez at gmail dot com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Redis nor the names of its contributors may be used
* to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <pthread.h>
#ifndef __ATOMIC_VAR_H
#define __ATOMIC_VAR_H
/* To test Redis with Helgrind (a Valgrind tool) it is useful to define
* the following macro, so that __sync macros are used: those can be detected
* by Helgrind (even if they are less efficient) so that no false positive
* is reported. */
// #define __ATOMIC_VAR_FORCE_SYNC_MACROS
#if !defined(__ATOMIC_VAR_FORCE_SYNC_MACROS) && defined(__ATOMIC_RELAXED) && !defined(__sun) && (!defined(__clang__) || !defined(__APPLE__) || __apple_build_version__ > 4210057)
/* Implementation using __atomic macros. */
#define atomicIncr(var,count) __atomic_add_fetch(&var,(count),__ATOMIC_RELAXED)
#define atomicGetIncr(var,oldvalue_var,count) do { \
oldvalue_var = __atomic_fetch_add(&var,(count),__ATOMIC_RELAXED); \
} while(0)
#define atomicDecr(var,count) __atomic_sub_fetch(&var,(count),__ATOMIC_RELAXED)
#define atomicGet(var,dstvar) do { \
dstvar = __atomic_load_n(&var,__ATOMIC_RELAXED); \
} while(0)
#define atomicSet(var,value) __atomic_store_n(&var,value,__ATOMIC_RELAXED)
#define REDIS_ATOMIC_API "atomic-builtin"
#elif defined(HAVE_ATOMIC)
/* Implementation using __sync macros. */
#define atomicIncr(var,count) __sync_add_and_fetch(&var,(count))
#define atomicGetIncr(var,oldvalue_var,count) do { \
oldvalue_var = __sync_fetch_and_add(&var,(count)); \
} while(0)
#define atomicDecr(var,count) __sync_sub_and_fetch(&var,(count))
#define atomicGet(var,dstvar) do { \
dstvar = __sync_sub_and_fetch(&var,0); \
} while(0)
#define atomicSet(var,value) do { \
while(!__sync_bool_compare_and_swap(&var,var,value)); \
} while(0)
#define REDIS_ATOMIC_API "sync-builtin"
#else
/* Implementation using pthread mutex. */
#define atomicIncr(var,count) do { \
pthread_mutex_lock(&var ## _mutex); \
var += (count); \
pthread_mutex_unlock(&var ## _mutex); \
} while(0)
#define atomicGetIncr(var,oldvalue_var,count) do { \
pthread_mutex_lock(&var ## _mutex); \
oldvalue_var = var; \
var += (count); \
pthread_mutex_unlock(&var ## _mutex); \
} while(0)
#define atomicDecr(var,count) do { \
pthread_mutex_lock(&var ## _mutex); \
var -= (count); \
pthread_mutex_unlock(&var ## _mutex); \
} while(0)
#define atomicGet(var,dstvar) do { \
pthread_mutex_lock(&var ## _mutex); \
dstvar = var; \
pthread_mutex_unlock(&var ## _mutex); \
} while(0)
#define atomicSet(var,value) do { \
pthread_mutex_lock(&var ## _mutex); \
var = value; \
pthread_mutex_unlock(&var ## _mutex); \
} while(0)
#define REDIS_ATOMIC_API "pthread-mutex"
#endif
#endif /* __ATOMIC_VAR_H */
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