134 lines
5.2 KiB
C
134 lines
5.2 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) -- Increment the atomic counter
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* atomicGetIncr(var,oldvalue_var,count) -- Get and increment the atomic counter
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* atomicDecr(var,count) -- Decrement the atomic counter
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* atomicGet(var,dstvar) -- Fetch the atomic counter value
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* atomicSet(var,value) -- Set the atomic counter value
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*
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* The variable 'var' should also have a declared mutex with the same
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* name and the "_mutex" postfix, for instance:
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*
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* long myvar;
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* pthread_mutex_t myvar_mutex;
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* atomicSet(myvar,12345);
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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, instead use the AtomicGetIncr()
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* if you need to get the current value and increment it atomically, like
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* in the followign example:
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*
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* long oldvalue;
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* atomicGetIncr(myvar,oldvalue,1);
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* doSomethingWith(oldvalue);
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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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/* To test Redis with Helgrind (a Valgrind tool) it is useful to define
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* the following macro, so that __sync macros are used: those can be detected
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* by Helgrind (even if they are less efficient) so that no false positive
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* is reported. */
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// #define __ATOMIC_VAR_FORCE_SYNC_MACROS
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#if !defined(__ATOMIC_VAR_FORCE_SYNC_MACROS) && defined(__ATOMIC_RELAXED) && !defined(__sun) && (!defined(__clang__) || !defined(__APPLE__) || __apple_build_version__ > 4210057)
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/* Implementation using __atomic macros. */
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#define atomicIncr(var,count) __atomic_add_fetch(&var,(count),__ATOMIC_RELAXED)
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#define atomicGetIncr(var,oldvalue_var,count) do { \
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oldvalue_var = __atomic_fetch_add(&var,(count),__ATOMIC_RELAXED); \
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} while(0)
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#define atomicDecr(var,count) __atomic_sub_fetch(&var,(count),__ATOMIC_RELAXED)
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#define atomicGet(var,dstvar) do { \
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dstvar = __atomic_load_n(&var,__ATOMIC_RELAXED); \
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} while(0)
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#define atomicSet(var,value) __atomic_store_n(&var,value,__ATOMIC_RELAXED)
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#define REDIS_ATOMIC_API "atomic-builtin"
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#elif defined(HAVE_ATOMIC)
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/* Implementation using __sync macros. */
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#define atomicIncr(var,count) __sync_add_and_fetch(&var,(count))
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#define atomicGetIncr(var,oldvalue_var,count) do { \
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oldvalue_var = __sync_fetch_and_add(&var,(count)); \
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} while(0)
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#define atomicDecr(var,count) __sync_sub_and_fetch(&var,(count))
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#define atomicGet(var,dstvar) do { \
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dstvar = __sync_sub_and_fetch(&var,0); \
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} while(0)
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#define atomicSet(var,value) do { \
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while(!__sync_bool_compare_and_swap(&var,var,value)); \
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} while(0)
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#define REDIS_ATOMIC_API "sync-builtin"
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#else
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/* Implementation using pthread mutex. */
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#define atomicIncr(var,count) do { \
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pthread_mutex_lock(&var ## _mutex); \
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var += (count); \
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pthread_mutex_unlock(&var ## _mutex); \
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} while(0)
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#define atomicGetIncr(var,oldvalue_var,count) do { \
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pthread_mutex_lock(&var ## _mutex); \
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oldvalue_var = var; \
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var += (count); \
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pthread_mutex_unlock(&var ## _mutex); \
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} while(0)
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#define atomicDecr(var,count) do { \
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pthread_mutex_lock(&var ## _mutex); \
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var -= (count); \
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pthread_mutex_unlock(&var ## _mutex); \
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} while(0)
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#define atomicGet(var,dstvar) do { \
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pthread_mutex_lock(&var ## _mutex); \
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dstvar = var; \
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pthread_mutex_unlock(&var ## _mutex); \
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} while(0)
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#define atomicSet(var,value) do { \
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pthread_mutex_lock(&var ## _mutex); \
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var = value; \
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pthread_mutex_unlock(&var ## _mutex); \
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} while(0)
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#define REDIS_ATOMIC_API "pthread-mutex"
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#endif
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#endif /* __ATOMIC_VAR_H */
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