q = (struct sem_queue *)((char *)walk - offset);
walk = walk->next;
+ /* If we are scanning the single sop, per-semaphore list of
+ * one semaphore and that semaphore is 0, then it is not
+ * necessary to scan the "alter" entries: simple increments
+ * that affect only one entry succeed immediately and cannot
+ * be in the per semaphore pending queue, and decrements
+ * cannot be successful if the value is already 0.
+ */
+ if (semnum != -1 && sma->sem_base[semnum].semval == 0 &&
+ q->alter)
+ break;
+
error = try_atomic_semop(sma, q->sops, q->nsops,
q->undo, q->pid);
static int semctl_nolock(struct ipc_namespace *ns, int semid,
int cmd, int version, union semun arg)
{
- int err = -EINVAL;
+ int err;
struct sem_array *sma;
switch(cmd) {
default:
return -EINVAL;
}
- return err;
out_unlock:
sem_unlock(sma);
return err;