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>
diff --git a/ipc/sem.c b/ipc/sem.c
index a7e40ed..70480a3 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -752,19 +752,29 @@
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 @@
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)
