diff options
| -rw-r--r-- | pthread_mutex_timedlock.c | 350 |
1 files changed, 182 insertions, 168 deletions
diff --git a/pthread_mutex_timedlock.c b/pthread_mutex_timedlock.c index c553a53..6a1c0a7 100644 --- a/pthread_mutex_timedlock.c +++ b/pthread_mutex_timedlock.c @@ -60,8 +60,10 @@ ptw32_timed_semwait (sem_t * sem, const struct timespec * abstime) * If 'abstime' is a NULL pointer then this function will * block until it can successfully decrease the value or * until interrupted by a signal. - * - * Unlike sem_timedwait(), this routine is not a cancelation point. + * + * Unlike sem_timedwait(), this routine is not a cancelation point. + * + * Unlike sem_timedwait(), this routine is non-cancelable. * * RESULTS * 2 abstime has passed already @@ -101,58 +103,57 @@ ptw32_timed_semwait (sem_t * sem, const struct timespec * abstime) else { if (abstime == NULL) - { - milliseconds = INFINITE; - } + { + milliseconds = INFINITE; + } else - { - /* - * Calculate timeout as milliseconds from current system time. - */ + { + /* + * Calculate timeout as milliseconds from current system time. + */ - /* get current system time */ + /* get current system time */ #ifdef NEED_FTIME - { - FILETIME ft; - SYSTEMTIME st; - - GetSystemTime(&st); - SystemTimeToFileTime(&st, &ft); - /* - * GetSystemTimeAsFileTime(&ft); would be faster, - * but it does not exist on WinCE - */ + { + FILETIME ft; + SYSTEMTIME st; - ptw32_filetime_to_timespec(&ft, &currSysTime); - } + GetSystemTime(&st); + SystemTimeToFileTime(&st, &ft); + /* + * GetSystemTimeAsFileTime(&ft); would be faster, + * but it does not exist on WinCE + */ + + ptw32_filetime_to_timespec(&ft, &currSysTime); + } - /* - * subtract current system time from abstime - */ - milliseconds = (abstime->tv_sec - currSysTime.tv_sec) * MILLISEC_PER_SEC; - milliseconds += ((abstime->tv_nsec - currSysTime.tv_nsec) - + (NANOSEC_PER_MILLISEC/2)) / NANOSEC_PER_MILLISEC; + /* + * subtract current system time from abstime + */ + milliseconds = (abstime->tv_sec - currSysTime.tv_sec) * MILLISEC_PER_SEC; + milliseconds += ((abstime->tv_nsec - currSysTime.tv_nsec) + + (NANOSEC_PER_MILLISEC/2)) / NANOSEC_PER_MILLISEC; #else /* NEED_FTIME */ - _ftime(&currSysTime); + _ftime(&currSysTime); - /* - * subtract current system time from abstime - */ - milliseconds = (abstime->tv_sec - currSysTime.time) * MILLISEC_PER_SEC; - milliseconds += ((abstime->tv_nsec + (NANOSEC_PER_MILLISEC/2)) / NANOSEC_PER_MILLISEC) + /* + * subtract current system time from abstime + */ + milliseconds = (abstime->tv_sec - currSysTime.time) * MILLISEC_PER_SEC; + milliseconds += ((abstime->tv_nsec + (NANOSEC_PER_MILLISEC/2)) / NANOSEC_PER_MILLISEC) - currSysTime.millitm; #endif /* NEED_FTIME */ - - if (((int) milliseconds) < 0) - { - return 2; - } - } + if (((int) milliseconds) < 0) + { + return 2; + } + } #ifdef NEED_SEM @@ -165,24 +166,24 @@ ptw32_timed_semwait (sem_t * sem, const struct timespec * abstime) #endif if (status == WAIT_OBJECT_0) - { + { #ifdef NEED_SEM - ptw32_decrease_semaphore(sem); + ptw32_decrease_semaphore(sem); #endif /* NEED_SEM */ - return 0; - } + return 0; + } else if (status == WAIT_TIMEOUT) - { - return 1; - } + { + return 1; + } else - { - result = EINVAL; - } + { + result = EINVAL; + } } if (result != 0) @@ -221,9 +222,9 @@ pthread_mutex_timedlock(pthread_mutex_t *mutex, const struct timespec *abstime) if (*mutex == PTHREAD_MUTEX_INITIALIZER) { if ((result = ptw32_mutex_check_need_init(mutex)) != 0) - { - return(result); - } + { + return(result); + } } mx = *mutex; @@ -232,126 +233,139 @@ pthread_mutex_timedlock(pthread_mutex_t *mutex, const struct timespec *abstime) { mx->recursive_count = 1; mx->ownerThread = (mx->kind != PTHREAD_MUTEX_FAST_NP - ? pthread_self() - : (pthread_t) PTW32_MUTEX_OWNER_ANONYMOUS); + ? pthread_self() + : (pthread_t) PTW32_MUTEX_OWNER_ANONYMOUS); } else { if( mx->kind != PTHREAD_MUTEX_FAST_NP && - pthread_equal( mx->ownerThread, pthread_self() ) ) - { - (void) InterlockedDecrement( &mx->lock_idx ); - - if( mx->kind == PTHREAD_MUTEX_RECURSIVE_NP ) - { - mx->recursive_count++; - } - else - { - result = EDEADLK; - } - } + pthread_equal( mx->ownerThread, pthread_self() ) ) + { + (void) InterlockedDecrement( &mx->lock_idx ); + + if( mx->kind == PTHREAD_MUTEX_RECURSIVE_NP ) + { + mx->recursive_count++; + } + else + { + result = EDEADLK; + } + } else - { - if (abstime == NULL) - { - result = EINVAL; - } - 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. */ - { - 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 == sem_trywait( &mx->wait_sema ) ) - { - (void) InterlockedDecrement( &mx->lock_idx ); - result = ETIMEDOUT; - } - - LeaveCriticalSection(&mx->wait_cs); - 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; - } - } - } - } + { + if (abstime == NULL) + { + result = EINVAL; + } + 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; + } + } + } + } } return(result); |