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Diffstat (limited to 'src/atomicvar.h')
| -rw-r--r-- | src/atomicvar.h | 158 |
1 files changed, 158 insertions, 0 deletions
diff --git a/src/atomicvar.h b/src/atomicvar.h new file mode 100644 index 0000000..2c2969c --- /dev/null +++ b/src/atomicvar.h @@ -0,0 +1,158 @@ +/* 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) do { \ + 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 */ |