diff options
| author | Manfred Spraul <manfred@colorfullife.com> | 2013-05-26 13:08:52 +0400 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-05-27 02:14:51 +0400 |
| commit | ab465df9dda42a997f7537c875127eeb6a88158c (patch) | |
| tree | 28a1ec28c15f1b59c938b7757c8f56eed0de0ecd /ipc/sem.c | |
| parent | 89ff77837a67994e4a4a20bb648687fbcc3083f2 (diff) | |
| download | linux-ab465df9dda42a997f7537c875127eeb6a88158c.tar.xz | |
ipc/sem.c: Fix missing wakeups in do_smart_update_queue()
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>
Diffstat (limited to 'ipc/sem.c')
| -rw-r--r-- | ipc/sem.c | 27 |
1 files changed, 22 insertions, 5 deletions
diff --git a/ipc/sem.c b/ipc/sem.c index a7e40ed8a076..70480a3aa698 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -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) |