MDEV-8111 - remove "fast mutexes"

They aren't faster than normal mutexes. They're disabled by default for years,
so de facto it's dead code, never used.

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) */