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-rw-r--r--ipc/sem.c34
1 files changed, 13 insertions, 21 deletions
diff --git a/ipc/sem.c b/ipc/sem.c
index d61362b..910c7a3 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)
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