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ipc/sem.c: Fix missing wakeups in do_smart_update_queue()

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do_smart_update_queue() is called when an operation (semop,
semctl(SETVAL), semctl(SETALL), ...) modified the array.  It must check
which of the sleeping tasks can proceed.

do_smart_update_queue() missed a few wakeups:
 - if a sleeping complex op was completed, then all per-semaphore queues
   must be scanned - not only those that were modified by *sops
 - if a sleeping simple op proceeded, then the global queue must be
   scanned again

And:
 - the test for "|sops == NULL) before scanning the global queue is not
   required: If the global queue is empty, then it doesn't need to be
   scanned - regardless of the reason for calling do_smart_update_queue()

The patch is not optimized, i.e.  even completing a wait-for-zero
operation causes a rescan.  This is done to keep the patch as simple as
possible.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Acked-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Manfred Spraul 2013-05-26 11:08:52 +02:00 committed by Linus Torvalds
parent 89ff77837a
commit ab465df9dd
1 changed files with 22 additions and 5 deletions
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27
ipc/sem.c
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@ -752,19 +752,29 @@ static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsop
int otime, struct list_head *pt)
{
int i;
int progress;
if (sma->complex_count || sops == NULL) {
if (update_queue(sma, -1, pt))
progress = 1;
retry_global:
if (sma->complex_count) {
if (update_queue(sma, -1, pt)) {
progress = 1;
otime = 1;
sops = NULL;
}
}
if (!progress)
goto done;
if (!sops) {
/* No semops; something special is going on. */
for (i = 0; i < sma->sem_nsems; i++) {
if (update_queue(sma, i, pt))
if (update_queue(sma, i, pt)) {
otime = 1;
progress = 1;
}
}
goto done;
goto done_checkretry;
}
/* Check the semaphores that were modified. */
@ -772,8 +782,15 @@ static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsop
if (sops[i].sem_op > 0 ||
(sops[i].sem_op < 0 &&
sma->sem_base[sops[i].sem_num].semval == 0))
if (update_queue(sma, sops[i].sem_num, pt))
if (update_queue(sma, sops[i].sem_num, pt)) {
otime = 1;
progress = 1;
}
}
done_checkretry:
if (progress) {
progress = 0;
goto retry_global;
}
done:
if (otime)