diff options
| -rw-r--r-- | ipc/sem.c | 51 |
1 files changed, 40 insertions, 11 deletions
@@ -434,17 +434,45 @@ static void unlink_queue(struct sem_array *sma, struct sem_queue *q) sma->complex_count--; } -/* Go through the pending queue for the indicated semaphore - * looking for tasks that can be completed. + +/** + * update_queue(sma, semnum): Look for tasks that can be completed. + * @sma: semaphore array. + * @semnum: semaphore that was modified. + * + * update_queue must be called after a semaphore in a semaphore array + * was modified. If multiple semaphore were modified, then @semnum + * must be set to -1. */ -static void update_queue (struct sem_array * sma) +static void update_queue(struct sem_array *sma, int semnum) { - struct sem_queue *q, *tq; + struct sem_queue *q; + struct list_head *walk; + struct list_head *pending_list; + int offset; + + /* if there are complex operations around, then knowing the semaphore + * that was modified doesn't help us. Assume that multiple semaphores + * were modified. + */ + if (sma->complex_count) + semnum = -1; + + if (semnum == -1) { + pending_list = &sma->sem_pending; + offset = offsetof(struct sem_queue, list); + } else { + pending_list = &sma->sem_base[semnum].sem_pending; + offset = offsetof(struct sem_queue, simple_list); + } again: - list_for_each_entry_safe(q, tq, &sma->sem_pending, list) { - int error; - int alter; + walk = pending_list->next; + while (walk != pending_list) { + int error, alter; + + q = (struct sem_queue *)((char *)walk - offset); + walk = walk->next; error = try_atomic_semop(sma, q->sops, q->nsops, q->undo, q->pid); @@ -769,7 +797,7 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum, } sma->sem_ctime = get_seconds(); /* maybe some queued-up processes were waiting for this */ - update_queue(sma); + update_queue(sma, -1); err = 0; goto out_unlock; } @@ -811,7 +839,7 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum, curr->sempid = task_tgid_vnr(current); sma->sem_ctime = get_seconds(); /* maybe some queued-up processes were waiting for this */ - update_queue(sma); + update_queue(sma, semnum); err = 0; goto out_unlock; } @@ -1187,7 +1215,8 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, error = try_atomic_semop (sma, sops, nsops, un, task_tgid_vnr(current)); if (error <= 0) { if (alter && error == 0) - update_queue (sma); + update_queue(sma, (nsops == 1) ? sops[0].sem_num : -1); + goto out_unlock_free; } @@ -1388,7 +1417,7 @@ void exit_sem(struct task_struct *tsk) } sma->sem_otime = get_seconds(); /* maybe some queued-up processes were waiting for this */ - update_queue(sma); + update_queue(sma, -1); sem_unlock(sma); call_rcu(&un->rcu, free_un); |