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authorManfred Spraul <manfred@colorfullife.com>2009-12-16 00:47:31 (GMT)
committerLinus Torvalds <torvalds@linux-foundation.org>2009-12-16 15:20:09 (GMT)
commitb6e90822e77cd476c18410f7003197d466e36ac6 (patch)
tree2ff18df8c024ae92e7e8912186c34b10b4b6f4bd /ipc
parentd4212093dca95c1f52197017d969cc66d5d962aa (diff)
ipc/sem.c: optimize if semops fail
Reduce the amount of scanning of the list of pending semaphore operations: If try_atomic_semop failed, then no changes were applied. Thus no need to restart. Additionally, this patch correct an incorrect comment: It's possible to wait for arbitrary semaphore values (do a dec by <x>, wait-for-zero, inc by <x> in one atomic operation) Both changes are from Nick Piggin, the patch is the result of a different split of the individual changes. Signed-off-by: Manfred Spraul <manfred@colorfullife.com> Cc: Nick Piggin <npiggin@suse.de> Cc: Pierre Peiffer <peifferp@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc')
-rw-r--r--ipc/sem.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/ipc/sem.c b/ipc/sem.c
index 2705fbb..eac3f46 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -445,13 +445,13 @@ again:
* of the completed operation:
* - if the operation modified the array, then restart from the
* head of the queue and check for threads that might be
- * waiting for semaphore values to become 0.
+ * waiting for the new semaphore values.
* - if the operation didn't modify the array, then just
* continue.
*/
alter = q->alter;
wake_up_sem_queue(q, error);
- if (alter)
+ if (alter && !error)
goto again;
}
}

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