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atomicvar.h
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atomicvar.h
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/* This file implements atomic counters using c11 _Atomic, __atomic or __sync
* macros if available, otherwise we will throw an error when compile.
*
* 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
* atomicGetWithSync(var,value) -- 'atomicGet' with inter-thread synchronization
* atomicSetWithSync(var,value) -- 'atomicSet' with inter-thread synchronization
*
* 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 following 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>
// #include "config.h"
#ifndef __ATOMIC_VAR_H
#define __ATOMIC_VAR_H
/* Define redisAtomic for atomic variable. */
#define redisAtomic
/* 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
/* There will be many false positives if we test Redis with Helgrind, since
* Helgrind can't understand we have imposed ordering on the program, so
* we use macros in helgrind.h to tell Helgrind inter-thread happens-before
* relationship explicitly for avoiding false positives.
*
* For more details, please see: valgrind/helgrind.h and
* https://www.valgrind.org/docs/manual/hg-manual.html#hg-manual.effective-use
*
* These macros take effect only when 'make helgrind', and you must first
* install Valgrind in the default path configuration. */
#ifdef __ATOMIC_VAR_FORCE_SYNC_MACROS
#include <valgrind/helgrind.h>
#else
#define ANNOTATE_HAPPENS_BEFORE(v) ((void) v)
#define ANNOTATE_HAPPENS_AFTER(v) ((void) v)
#endif
#if !defined(__ATOMIC_VAR_FORCE_SYNC_MACROS) && defined(__STDC_VERSION__) && \
(__STDC_VERSION__ >= 201112L) && !defined(__STDC_NO_ATOMICS__)
/* Use '_Atomic' keyword if the compiler supports. */
#undef redisAtomic
#define redisAtomic _Atomic
/* Implementation using _Atomic in C11. */
#include <stdatomic.h>
#define atomicIncr(var,count) atomic_fetch_add_explicit(&var,(count),memory_order_relaxed)
#define atomicGetIncr(var,oldvalue_var,count) do { \
oldvalue_var = atomic_fetch_add_explicit(&var,(count),memory_order_relaxed); \
} while(0)
#define atomicDecr(var,count) atomic_fetch_sub_explicit(&var,(count),memory_order_relaxed)
#define atomicGet(var,dstvar) do { \
dstvar = atomic_load_explicit(&var,memory_order_relaxed); \
} while(0)
#define atomicSet(var,value) atomic_store_explicit(&var,value,memory_order_relaxed)
#define atomicGetWithSync(var,dstvar) do { \
dstvar = atomic_load_explicit(&var,memory_order_seq_cst); \
} while(0)
#define atomicSetWithSync(var,value) \
atomic_store_explicit(&var,value,memory_order_seq_cst)
#define REDIS_ATOMIC_API "c11-builtin"
#elif !defined(__ATOMIC_VAR_FORCE_SYNC_MACROS) && \
(!defined(__clang__) || !defined(__APPLE__) || __apple_build_version__ > 4210057) && \
defined(__ATOMIC_RELAXED) && defined(__ATOMIC_SEQ_CST)
/* 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 atomicGetWithSync(var,dstvar) do { \
dstvar = __atomic_load_n(&var,__ATOMIC_SEQ_CST); \
} while(0)
#define atomicSetWithSync(var,value) \
__atomic_store_n(&var,value,__ATOMIC_SEQ_CST)
#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)
/* Actually the builtin issues a full memory barrier by default. */
#define atomicGetWithSync(var,dstvar) { \
dstvar = __sync_sub_and_fetch(&var,0,__sync_synchronize); \
ANNOTATE_HAPPENS_AFTER(&var); \
} while(0)
#define atomicSetWithSync(var,value) do { \
ANNOTATE_HAPPENS_BEFORE(&var); \
while(!__sync_bool_compare_and_swap(&var,var,value,__sync_synchronize)); \
} while(0)
#define REDIS_ATOMIC_API "sync-builtin"
#else
#error "Unable to determine atomic operations for your platform"
#endif
#endif /* __ATOMIC_VAR_H */