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Member "wrk-4.2.0/src/atomicvar.h" (7 Feb 2021, 5367 Bytes) of package /linux/www/wrk-4.2.0.tar.gz:


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    1 /* This file implements atomic counters using __atomic or __sync macros if
    2  * available, otherwise synchronizing different threads using a mutex.
    3  *
    4  * The exported interaface is composed of three macros:
    5  *
    6  * atomicIncr(var,count) -- Increment the atomic counter
    7  * atomicGetIncr(var,oldvalue_var,count) -- Get and increment the atomic counter
    8  * atomicDecr(var,count) -- Decrement the atomic counter
    9  * atomicGet(var,dstvar) -- Fetch the atomic counter value
   10  * atomicSet(var,value)  -- Set the atomic counter value
   11  *
   12  * The variable 'var' should also have a declared mutex with the same
   13  * name and the "_mutex" postfix, for instance:
   14  *
   15  *  long myvar;
   16  *  pthread_mutex_t myvar_mutex;
   17  *  atomicSet(myvar,12345);
   18  *
   19  * If atomic primitives are availble (tested in config.h) the mutex
   20  * is not used.
   21  *
   22  * Never use return value from the macros, instead use the AtomicGetIncr()
   23  * if you need to get the current value and increment it atomically, like
   24  * in the followign example:
   25  *
   26  *  long oldvalue;
   27  *  atomicGetIncr(myvar,oldvalue,1);
   28  *  doSomethingWith(oldvalue);
   29  *
   30  * ----------------------------------------------------------------------------
   31  *
   32  * Copyright (c) 2015, Salvatore Sanfilippo <antirez at gmail dot com>
   33  * All rights reserved.
   34  *
   35  * Redistribution and use in source and binary forms, with or without
   36  * modification, are permitted provided that the following conditions are met:
   37  *
   38  *   * Redistributions of source code must retain the above copyright notice,
   39  *     this list of conditions and the following disclaimer.
   40  *   * Redistributions in binary form must reproduce the above copyright
   41  *     notice, this list of conditions and the following disclaimer in the
   42  *     documentation and/or other materials provided with the distribution.
   43  *   * Neither the name of Redis nor the names of its contributors may be used
   44  *     to endorse or promote products derived from this software without
   45  *     specific prior written permission.
   46  *
   47  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   48  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   49  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   50  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
   51  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   52  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   53  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   54  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   55  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   56  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   57  * POSSIBILITY OF SUCH DAMAGE.
   58  */
   59 
   60 #include <pthread.h>
   61 
   62 #ifndef __ATOMIC_VAR_H
   63 #define __ATOMIC_VAR_H
   64 
   65 /* To test Redis with Helgrind (a Valgrind tool) it is useful to define
   66  * the following macro, so that __sync macros are used: those can be detected
   67  * by Helgrind (even if they are less efficient) so that no false positive
   68  * is reported. */
   69 // #define __ATOMIC_VAR_FORCE_SYNC_MACROS
   70 
   71 #if !defined(__ATOMIC_VAR_FORCE_SYNC_MACROS) && defined(__ATOMIC_RELAXED) && !defined(__sun) && (!defined(__clang__) || !defined(__APPLE__) || __apple_build_version__ > 4210057)
   72 /* Implementation using __atomic macros. */
   73 
   74 #define atomicIncr(var,count) __atomic_add_fetch(&var,(count),__ATOMIC_RELAXED)
   75 #define atomicGetIncr(var,oldvalue_var,count) do { \
   76     oldvalue_var = __atomic_fetch_add(&var,(count),__ATOMIC_RELAXED); \
   77 } while(0)
   78 #define atomicDecr(var,count) __atomic_sub_fetch(&var,(count),__ATOMIC_RELAXED)
   79 #define atomicGet(var,dstvar) do { \
   80     dstvar = __atomic_load_n(&var,__ATOMIC_RELAXED); \
   81 } while(0)
   82 #define atomicSet(var,value) __atomic_store_n(&var,value,__ATOMIC_RELAXED)
   83 #define REDIS_ATOMIC_API "atomic-builtin"
   84 
   85 #elif defined(HAVE_ATOMIC)
   86 /* Implementation using __sync macros. */
   87 
   88 #define atomicIncr(var,count) __sync_add_and_fetch(&var,(count))
   89 #define atomicGetIncr(var,oldvalue_var,count) do { \
   90     oldvalue_var = __sync_fetch_and_add(&var,(count)); \
   91 } while(0)
   92 #define atomicDecr(var,count) __sync_sub_and_fetch(&var,(count))
   93 #define atomicGet(var,dstvar) do { \
   94     dstvar = __sync_sub_and_fetch(&var,0); \
   95 } while(0)
   96 #define atomicSet(var,value) do { \
   97     while(!__sync_bool_compare_and_swap(&var,var,value)); \
   98 } while(0)
   99 #define REDIS_ATOMIC_API "sync-builtin"
  100 
  101 #else
  102 /* Implementation using pthread mutex. */
  103 
  104 #define atomicIncr(var,count) do { \
  105     pthread_mutex_lock(&var ## _mutex); \
  106     var += (count); \
  107     pthread_mutex_unlock(&var ## _mutex); \
  108 } while(0)
  109 #define atomicGetIncr(var,oldvalue_var,count) do { \
  110     pthread_mutex_lock(&var ## _mutex); \
  111     oldvalue_var = var; \
  112     var += (count); \
  113     pthread_mutex_unlock(&var ## _mutex); \
  114 } while(0)
  115 #define atomicDecr(var,count) do { \
  116     pthread_mutex_lock(&var ## _mutex); \
  117     var -= (count); \
  118     pthread_mutex_unlock(&var ## _mutex); \
  119 } while(0)
  120 #define atomicGet(var,dstvar) do { \
  121     pthread_mutex_lock(&var ## _mutex); \
  122     dstvar = var; \
  123     pthread_mutex_unlock(&var ## _mutex); \
  124 } while(0)
  125 #define atomicSet(var,value) do { \
  126     pthread_mutex_lock(&var ## _mutex); \
  127     var = value; \
  128     pthread_mutex_unlock(&var ## _mutex); \
  129 } while(0)
  130 #define REDIS_ATOMIC_API "pthread-mutex"
  131 
  132 #endif
  133 #endif /* __ATOMIC_VAR_H */