diff options
Diffstat (limited to 'nuttx/sched/sem_wait.c')
| -rw-r--r-- | nuttx/sched/sem_wait.c | 21 |
1 files changed, 15 insertions, 6 deletions
diff --git a/nuttx/sched/sem_wait.c b/nuttx/sched/sem_wait.c index 747d7cd48..12d8c98ca 100644 --- a/nuttx/sched/sem_wait.c +++ b/nuttx/sched/sem_wait.c @@ -1,7 +1,7 @@ /**************************************************************************** * sched/sem_wait.c * - * Copyright (C) 2007-2009 Gregory Nutt. All rights reserved. + * Copyright (C) 2007-2010 Gregory Nutt. All rights reserved. * Author: Gregory Nutt <spudmonkey@racsa.co.cr> * * Redistribution and use in source and binary forms, with or without @@ -178,6 +178,20 @@ int sem_wait(FAR sem_t *sem) * assigned to this thread of execution, or (2) the semaphore wait * has been interrupted by a signal. We can detect the latter case * be examining the errno value. + * + * In the event that the semaphore wait was interrupt was interrupted + * by a signal, certain semaphore clean-up operations have already been + * performed (see sem_waitirq.c). Specifically: + * + * - sem_canceled() was called to restore the priority of all threads + * that hold a reference to the semaphore, + * - The semaphore count was decremented, and + * - tcb->waitsem was nullifed. + * + * It is necesaary to do these things in sem_waitirq.c because a long + * time may elapse between the time that the signal was issued and + * this thread is awakened and this leaves a door open to several + * race conditions. */ if (errno != EINTR) @@ -187,11 +201,6 @@ int sem_wait(FAR sem_t *sem) sem_addholder(sem); ret = OK; } - else - { - sem_canceled(sem); - sem->semcount++; - } #ifdef CONFIG_PRIORITY_INHERITANCE sched_unlock(); |