diff options
Diffstat (limited to 'src/atomicvar.h')
| -rw-r--r-- | src/atomicvar.h | 109 |
1 files changed, 67 insertions, 42 deletions
diff --git a/src/atomicvar.h b/src/atomicvar.h index ecd26ad70..6ac04c605 100644 --- a/src/atomicvar.h +++ b/src/atomicvar.h @@ -1,5 +1,5 @@ -/* This file implements atomic counters using __atomic or __sync macros if - * available, otherwise synchronizing different threads using a mutex. +/* 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: * @@ -8,16 +8,8 @@ * 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. + * 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 @@ -58,17 +50,64 @@ */ #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 -#if !defined(__ATOMIC_VAR_FORCE_SYNC_MACROS) && defined(__ATOMIC_RELAXED) && !defined(__sun) && (!defined(__clang__) || !defined(__APPLE__) || __apple_build_version__ > 4210057) +/* 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(__sun) && \ + (!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) @@ -80,6 +119,11 @@ 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) @@ -96,38 +140,19 @@ #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 -/* 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" +#error "Unable to determine atomic operations for your platform" #endif #endif /* __ATOMIC_VAR_H */ |