From b0cf9efa6afeb8a7dbddf124dae173a2d633c801 Mon Sep 17 00:00:00 2001 From: rpj Date: Fri, 1 Oct 2004 07:17:09 +0000 Subject: Mutex speedups --- pthread_mutex_timedlock.c | 244 ++++++++++++++++++++++------------------------ 1 file changed, 118 insertions(+), 126 deletions(-) (limited to 'pthread_mutex_timedlock.c') diff --git a/pthread_mutex_timedlock.c b/pthread_mutex_timedlock.c index a5d6b59..58f5613 100644 --- a/pthread_mutex_timedlock.c +++ b/pthread_mutex_timedlock.c @@ -214,10 +214,9 @@ pthread_mutex_timedlock (pthread_mutex_t * mutex, return -1; #endif - if (mutex == NULL || *mutex == NULL) - { - return EINVAL; - } + /* + * Let the system deal with invalid pointers. + */ /* * We do a quick check to see if we need to do more work @@ -235,142 +234,135 @@ pthread_mutex_timedlock (pthread_mutex_t * mutex, mx = *mutex; - if (0 == InterlockedIncrement (&mx->lock_idx)) + if (mx->kind == PTHREAD_MUTEX_NORMAL) { - mx->recursive_count = 1; - mx->ownerThread = (mx->kind != PTHREAD_MUTEX_FAST_NP - ? pthread_self () - : (pthread_t) PTW32_MUTEX_OWNER_ANONYMOUS); + if (0 != InterlockedIncrement (&mx->lock_idx)) + { + switch (ptw32_timed_semwait (&mx->wait_sema, abstime)) + { + case 0: /* We got the mutex. */ + { + break; + } + case 1: /* Timed out. */ + case 2: /* abstime passed before we started to wait. */ + { + /* + * If we timeout, it is up to us to adjust lock_idx to say + * we're no longer waiting. + * + * The owner thread may still have posted wait_sema thinking + * we were waiting. We must check but then NOT do any + * programmed work if we have acquired the mutex because + * we don't know how long ago abstime was. We MUST just release it + * immediately. + */ + EnterCriticalSection (&mx->wait_cs); + + result = ETIMEDOUT; + + if (-1 == sem_trywait (&mx->wait_sema)) + { + (void) InterlockedDecrement (&mx->lock_idx); + } + else + { + if (InterlockedDecrement (&mx->lock_idx) >= 0) + { + /* Someone else is waiting on that mutex */ + if (sem_post (&mx->wait_sema) != 0) + { + result = errno; + } + } + } + + LeaveCriticalSection (&mx->wait_cs); + break; + } + default: + { + result = errno; + break; + } + } + } } else { - if (mx->kind != PTHREAD_MUTEX_FAST_NP && - pthread_equal (mx->ownerThread, pthread_self ())) - { - (void) InterlockedDecrement (&mx->lock_idx); + pthread_t self = pthread_self(); - if (mx->kind == PTHREAD_MUTEX_RECURSIVE_NP) - { - mx->recursive_count++; - } - else - { - result = EDEADLK; - } + if (0 == InterlockedIncrement (&mx->lock_idx)) + { + mx->recursive_count = 1; + mx->ownerThread = self; } else { - if (abstime == NULL) + if (pthread_equal (mx->ownerThread, self)) { - result = EINVAL; + (void) InterlockedDecrement (&mx->lock_idx); + + if (mx->kind == PTHREAD_MUTEX_RECURSIVE) + { + mx->recursive_count++; + } + else + { + result = EDEADLK; + } } else { switch (ptw32_timed_semwait (&mx->wait_sema, abstime)) { - case 0: /* We got the mutex. */ - { - mx->recursive_count = 1; - mx->ownerThread = (mx->kind != PTHREAD_MUTEX_FAST_NP - ? pthread_self () - : (pthread_t) - PTW32_MUTEX_OWNER_ANONYMOUS); - break; - } - case 1: /* Timedout, try a second grab. */ - { - int busy; - - EnterCriticalSection (&mx->wait_cs); - - /* - * If we timeout, it is up to us to adjust lock_idx to say - * we're no longer waiting. If the mutex was also unlocked - * while we were timing out, and we simply return ETIMEDOUT, - * then wait_sema would be left in a state that is not consistent - * with the state of lock_idx. - * - * We must check to see if wait_sema has just been posted - * but we can't just call sem_getvalue - we must compete for - * the semaphore using sem_trywait(), otherwise we would need - * additional critical sections elsewhere, which would make the - * logic too inefficient. - * - * If sem_trywait returns EAGAIN then either wait_sema - * was given directly to another waiting thread or - * another thread has called sem_*wait() before us and - * taken the lock. Then we MUST decrement lock_idx and return - * ETIMEDOUT. - * - * Otherwise we MUST return success (because we have effectively - * acquired the lock that would have been ours had we not - * timed out), and NOT decrement lock_idx. - * - * We can almost guarrantee that EAGAIN is the only - * possible error, so no need to test errno. - */ - - if (-1 == (busy = sem_trywait (&mx->wait_sema))) - { - (void) InterlockedDecrement (&mx->lock_idx); - result = ETIMEDOUT; - } - - LeaveCriticalSection (&mx->wait_cs); - - if (!busy) - { - /* - * We have acquired the lock on second grab - keep it. - */ - mx->recursive_count = 1; - mx->ownerThread = (mx->kind != PTHREAD_MUTEX_FAST_NP - ? pthread_self () - : (pthread_t) - PTW32_MUTEX_OWNER_ANONYMOUS); - } - break; - } - case 2: /* abstime passed before we started to wait. */ - { - /* - * If we timeout, it is up to us to adjust lock_idx to say - * we're no longer waiting. - * - * The owner thread may still have posted wait_sema thinking - * we were waiting. I believe we must check but then NOT do any - * programmed work if we have acquired the mutex because - * we don't how long ago abstime was. We MUST just release it - * immediately. - */ - EnterCriticalSection (&mx->wait_cs); - - result = ETIMEDOUT; - - if (-1 == sem_trywait (&mx->wait_sema)) - { - (void) InterlockedDecrement (&mx->lock_idx); - } - else - { - if (InterlockedDecrement (&mx->lock_idx) >= 0) - { - /* Someone else is waiting on that mutex */ - if (sem_post (&mx->wait_sema) != 0) - { - result = errno; - } - } - } - - LeaveCriticalSection (&mx->wait_cs); - break; - } - default: - { - result = errno; - break; - } + case 0: /* We got the mutex. */ + { + mx->recursive_count = 1; + mx->ownerThread = self; + break; + } + case 1: /* Timedout. */ + case 2: /* abstime passed before we started to wait. */ + { + /* + * If we timeout, it is up to us to adjust lock_idx to say + * we're no longer waiting. + * + * The owner thread may still have posted wait_sema thinking + * we were waiting. We must check but then NOT do any + * programmed work if we have acquired the mutex because + * we don't know how long ago abstime was. We MUST just release it + * immediately. + */ + EnterCriticalSection (&mx->wait_cs); + + result = ETIMEDOUT; + + if (-1 == sem_trywait (&mx->wait_sema)) + { + (void) InterlockedDecrement (&mx->lock_idx); + } + else + { + if (InterlockedDecrement (&mx->lock_idx) >= 0) + { + /* Someone else is waiting on that mutex */ + if (sem_post (&mx->wait_sema) != 0) + { + result = errno; + } + } + } + + LeaveCriticalSection (&mx->wait_cs); + break; + } + default: + { + result = errno; + break; + } } } } -- cgit v1.2.3