diff options
| -rw-r--r-- | ipc/sem.c | 38 |
1 files changed, 23 insertions, 15 deletions
diff --git a/ipc/sem.c b/ipc/sem.c index d377b3adfc3..2705fbbc437 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -398,6 +398,27 @@ undo: return result; } +/* + * Wake up a process waiting on the sem queue with a given error. + * The queue is invalid (may not be accessed) after the function returns. + */ +static void wake_up_sem_queue(struct sem_queue *q, int error) +{ + /* + * Hold preempt off so that we don't get preempted and have the + * wakee busy-wait until we're scheduled back on. We're holding + * locks here so it may not strictly be needed, however if the + * locks become preemptible then this prevents such a problem. + */ + preempt_disable(); + q->status = IN_WAKEUP; + wake_up_process(q->sleeper); + /* hands-off: q can disappear immediately after writing q->status. */ + smp_wmb(); + q->status = error; + preempt_enable(); +} + /* Go through the pending queue for the indicated semaphore * looking for tasks that can be completed. */ @@ -429,17 +450,7 @@ again: * continue. */ alter = q->alter; - - /* wake up the waiting thread */ - q->status = IN_WAKEUP; - - wake_up_process(q->sleeper); - /* hands-off: q will disappear immediately after - * writing q->status. - */ - smp_wmb(); - q->status = error; - + wake_up_sem_queue(q, error); if (alter) goto again; } @@ -523,10 +534,7 @@ static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp) list_for_each_entry_safe(q, tq, &sma->sem_pending, list) { list_del(&q->list); - q->status = IN_WAKEUP; - wake_up_process(q->sleeper); /* doesn't sleep */ - smp_wmb(); - q->status = -EIDRM; /* hands-off q */ + wake_up_sem_queue(q, -EIDRM); } /* Remove the semaphore set from the IDR */ |