diff options
| -rw-r--r-- | ipc/sem.c | 34 |
1 files changed, 13 insertions, 21 deletions
diff --git a/ipc/sem.c b/ipc/sem.c index d61362b31f1e..910c7a3865c8 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -993,38 +993,30 @@ static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsop } /* - * check_qop: Test how often a queued operation sleeps on the semaphore semnum + * check_qop: Test if a queued operation sleeps on the semaphore semnum */ static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q, bool count_zero) { - struct sembuf *sops = q->sops; - int nsops = q->nsops; - int i, semcnt; + struct sembuf *sop = q->blocking; - semcnt = 0; + if (sop->sem_num != semnum) + return 0; - for (i = 0; i < nsops; i++) { - if (sops[i].sem_num != semnum) - continue; - if (sops[i].sem_flg & IPC_NOWAIT) - continue; - if (count_zero && sops[i].sem_op == 0) - semcnt++; - if (!count_zero && sops[i].sem_op < 0) - semcnt++; - } - return semcnt; + if (count_zero && sop->sem_op == 0) + return 1; + if (!count_zero && sop->sem_op < 0) + return 1; + + return 0; } /* The following counts are associated to each semaphore: * semncnt number of tasks waiting on semval being nonzero * semzcnt number of tasks waiting on semval being zero - * This model assumes that a task waits on exactly one semaphore. - * Since semaphore operations are to be performed atomically, tasks actually - * wait on a whole sequence of semaphores simultaneously. - * The counts we return here are a rough approximation, but still - * warrant that semncnt+semzcnt>0 if the task is on the pending queue. + * + * Per definition, a task waits only on the semaphore of the first semop + * that cannot proceed, even if additional operation would block, too. */ static int count_semcnt(struct sem_array *sma, ushort semnum, bool count_zero) |