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| author | Manfred Spraul <manfred@colorfullife.com> | 2009-12-15 16:47:31 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-12-16 07:20:09 -0800 |
| commit | b6e90822e77cd476c18410f7003197d466e36ac6 (patch) | |
| tree | 2ff18df8c024ae92e7e8912186c34b10b4b6f4bd /ipc/sem.c | |
| parent | d4212093dca95c1f52197017d969cc66d5d962aa (diff) | |
| download | lwn-b6e90822e77cd476c18410f7003197d466e36ac6.tar.gz lwn-b6e90822e77cd476c18410f7003197d466e36ac6.zip | |
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/sem.c')
| -rw-r--r-- | ipc/sem.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/ipc/sem.c b/ipc/sem.c index 2705fbbc4374..eac3f46a5968 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; } } |