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authorNick Piggin <nickpiggin@yahoo.com.au>2005-06-23 03:08:52 -0400
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-23 12:45:16 -0400
commit250dccc00805e755a6d80a73557034253da0831f (patch)
treeda9f94abed8dac7479507601694d9276b2dbaf28 /drivers
parent040c928c47b591d1cd9977cd6431cae213528b45 (diff)
[PATCH] blk: no memory barrier
This memory barrier is not needed because the waitqueue will only get waiters on it in the following situations: rq->count has exceeded the threshold - however all manipulations of ->count are performed under the runqueue lock, and so we will correctly pick up any waiter. Memory allocation for the request fails. In this case, there is no additional help provided by the memory barrier. We are guaranteed to eventually wake up waiters because the request allocation mempool guarantees that if the mem allocation for a request fails, there must be some requests in flight. They will wake up waiters when they are retired. Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Jens Axboe <axboe@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/block/ll_rw_blk.c1
1 files changed, 0 insertions, 1 deletions
diff --git a/drivers/block/ll_rw_blk.c b/drivers/block/ll_rw_blk.c
index c581f9138c47..265de858d4de 100644
--- a/drivers/block/ll_rw_blk.c
+++ b/drivers/block/ll_rw_blk.c
@@ -1842,7 +1842,6 @@ static void __freed_request(request_queue_t *q, int rw)
1842 clear_queue_congested(q, rw); 1842 clear_queue_congested(q, rw);
1843 1843
1844 if (rl->count[rw] + 1 <= q->nr_requests) { 1844 if (rl->count[rw] + 1 <= q->nr_requests) {
1845 smp_mb();
1846 if (waitqueue_active(&rl->wait[rw])) 1845 if (waitqueue_active(&rl->wait[rw]))
1847 wake_up(&rl->wait[rw]); 1846 wake_up(&rl->wait[rw]);
1848 1847