diff options
Diffstat (limited to 'mysys/thr_rwlock.c')
| -rw-r--r-- | mysys/thr_rwlock.c | 56 |
1 files changed, 44 insertions, 12 deletions
diff --git a/mysys/thr_rwlock.c b/mysys/thr_rwlock.c index 0aa4d3fc3c4..2ac4a00695e 100644 --- a/mysys/thr_rwlock.c +++ b/mysys/thr_rwlock.c @@ -16,7 +16,8 @@ /* Synchronization - readers / writer thread locks */ #include "mysys_priv.h" -#if defined(THREAD) && !defined(HAVE_PTHREAD_RWLOCK_RDLOCK) && !defined(HAVE_RWLOCK_INIT) +#if defined(THREAD) +#if defined(NEED_MY_RW_LOCK) #include <errno.h> /* @@ -58,7 +59,7 @@ * Mountain View, California 94043 */ -int my_rwlock_init(rw_lock_t *rwp, void *arg __attribute__((unused))) +int my_rw_init(my_rw_lock_t *rwp, my_bool *prefer_readers_attr) { pthread_condattr_t cond_attr; @@ -70,12 +71,14 @@ int my_rwlock_init(rw_lock_t *rwp, void *arg __attribute__((unused))) rwp->state = 0; rwp->waiters = 0; + /* If attribute argument is NULL use default value - prefer writers. */ + rwp->prefer_readers= prefer_readers_attr ? *prefer_readers_attr : FALSE; return(0); } -int my_rwlock_destroy(rw_lock_t *rwp) +int my_rw_destroy(my_rw_lock_t *rwp) { pthread_mutex_destroy( &rwp->lock ); pthread_cond_destroy( &rwp->readers ); @@ -84,12 +87,13 @@ int my_rwlock_destroy(rw_lock_t *rwp) } -int my_rw_rdlock(rw_lock_t *rwp) +int my_rw_rdlock(my_rw_lock_t *rwp) { pthread_mutex_lock(&rwp->lock); /* active or queued writers */ - while (( rwp->state < 0 ) || rwp->waiters) + while (( rwp->state < 0 ) || + (rwp->waiters && ! rwp->prefer_readers)) pthread_cond_wait( &rwp->readers, &rwp->lock); rwp->state++; @@ -97,11 +101,12 @@ int my_rw_rdlock(rw_lock_t *rwp) return(0); } -int my_rw_tryrdlock(rw_lock_t *rwp) +int my_rw_tryrdlock(my_rw_lock_t *rwp) { int res; pthread_mutex_lock(&rwp->lock); - if ((rwp->state < 0 ) || rwp->waiters) + if ((rwp->state < 0 ) || + (rwp->waiters && ! rwp->prefer_readers)) res= EBUSY; /* Can't get lock */ else { @@ -113,7 +118,7 @@ int my_rw_tryrdlock(rw_lock_t *rwp) } -int my_rw_wrlock(rw_lock_t *rwp) +int my_rw_wrlock(my_rw_lock_t *rwp) { pthread_mutex_lock(&rwp->lock); rwp->waiters++; /* another writer queued */ @@ -127,7 +132,7 @@ int my_rw_wrlock(rw_lock_t *rwp) } -int my_rw_trywrlock(rw_lock_t *rwp) +int my_rw_trywrlock(my_rw_lock_t *rwp) { int res; pthread_mutex_lock(&rwp->lock); @@ -143,7 +148,7 @@ int my_rw_trywrlock(rw_lock_t *rwp) } -int my_rw_unlock(rw_lock_t *rwp) +int my_rw_unlock(my_rw_lock_t *rwp) { DBUG_PRINT("rw_unlock", ("state: %d waiters: %d", rwp->state, rwp->waiters)); @@ -160,7 +165,8 @@ int my_rw_unlock(rw_lock_t *rwp) } else { - if ( --rwp->state == 0 ) /* no more readers */ + if ( --rwp->state == 0 && /* no more readers */ + rwp->waiters) pthread_cond_signal( &rwp->writers ); } @@ -168,4 +174,30 @@ int my_rw_unlock(rw_lock_t *rwp) return(0); } -#endif + +int rw_pr_init(struct st_my_rw_lock_t *rwlock) +{ + my_bool prefer_readers_attr= TRUE; + return my_rw_init(rwlock, &prefer_readers_attr); +} + +#else + +/* + We are on system which has native read/write locks which support + preferring of readers. +*/ + +int rw_pr_init(rw_pr_lock_t *rwlock) +{ + pthread_rwlockattr_t rwlock_attr; + + pthread_rwlockattr_init(&rwlock_attr); + pthread_rwlockattr_setkind_np(&rwlock_attr, PTHREAD_RWLOCK_PREFER_READER_NP); + pthread_rwlock_init(rwlock, NULL); + pthread_rwlockattr_destroy(&rwlock_attr); + return 0; +} + +#endif /* defined(NEED_MY_RW_LOCK) */ +#endif /* defined(THREAD) */ |