diff options
Diffstat (limited to 'mysys/thr_mutex.c')
| -rw-r--r-- | mysys/thr_mutex.c | 86 |
1 files changed, 0 insertions, 86 deletions
diff --git a/mysys/thr_mutex.c b/mysys/thr_mutex.c index 18af5f47b10..4d6abd4ba66 100644 --- a/mysys/thr_mutex.c +++ b/mysys/thr_mutex.c @@ -105,8 +105,6 @@ void my_mutex_init() #if defined(SAFE_MUTEX_DEFINED) safe_mutex_global_init(); -#elif defined(MY_PTHREAD_FASTMUTEX) - fastmutex_global_init(); #endif } @@ -838,88 +836,4 @@ static void print_deadlock_warning(safe_mutex_t *new_mutex, DBUG_VOID_RETURN; } -#elif defined(MY_PTHREAD_FASTMUTEX) /* !SAFE_MUTEX_DEFINED */ - -static ulong mutex_delay(ulong delayloops) -{ - ulong i; - volatile ulong j; - - j = 0; - - for (i = 0; i < delayloops * 50; i++) - j += i; - - return(j); -} - -#define MY_PTHREAD_FASTMUTEX_SPINS 8 -#define MY_PTHREAD_FASTMUTEX_DELAY 4 - -static int cpu_count= 0; - -int my_pthread_fastmutex_init(my_pthread_fastmutex_t *mp, - const pthread_mutexattr_t *attr) -{ - if ((cpu_count > 1) && (attr == MY_MUTEX_INIT_FAST)) - mp->spins= MY_PTHREAD_FASTMUTEX_SPINS; - else - mp->spins= 0; - mp->rng_state= 1; - return pthread_mutex_init(&mp->mutex, attr); -} - -/** - Park-Miller random number generator. A simple linear congruential - generator that operates in multiplicative group of integers modulo n. - - x_{k+1} = (x_k g) mod n - - Popular pair of parameters: n = 2^32 − 5 = 4294967291 and g = 279470273. - The period of the generator is about 2^31. - Largest value that can be returned: 2147483646 (RAND_MAX) - - Reference: - - S. K. Park and K. W. Miller - "Random number generators: good ones are hard to find" - Commun. ACM, October 1988, Volume 31, No 10, pages 1192-1201. -*/ - -static double park_rng(my_pthread_fastmutex_t *mp) -{ - mp->rng_state= ((my_ulonglong)mp->rng_state * 279470273U) % 4294967291U; - return (mp->rng_state / 2147483647.0); -} - -int my_pthread_fastmutex_lock(my_pthread_fastmutex_t *mp) -{ - int res; - uint i; - uint maxdelay= MY_PTHREAD_FASTMUTEX_DELAY; - - for (i= 0; i < mp->spins; i++) - { - res= pthread_mutex_trylock(&mp->mutex); - - if (res == 0) - return 0; - - if (res != EBUSY) - return res; - - mutex_delay(maxdelay); - maxdelay += park_rng(mp) * MY_PTHREAD_FASTMUTEX_DELAY + 1; - } - return pthread_mutex_lock(&mp->mutex); -} - - -void fastmutex_global_init(void) -{ -#ifdef _SC_NPROCESSORS_CONF - cpu_count= sysconf(_SC_NPROCESSORS_CONF); #endif -} - -#endif /* defined(MY_PTHREAD_FASTMUTEX) && defined(SAFE_MUTEX_DEFINED) */ |