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Date: Sat, 3 Oct 2009 19:19:21 +0200 From: manfred@...orfullife.com To: linux-kernel@...r.kernel.org Cc: Manfred Spraul <manfred@...orfullife.com> Subject: [PATCH 4/7] ipc/sem.c: optimize if semops fail From: Manfred Spraul <manfred@...orfullife.com> 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@...orfullife.com> --- ipc/sem.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/ipc/sem.c b/ipc/sem.c index 3629ef8..9425817 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -444,13 +444,13 @@ 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; } } -- 1.6.2.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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