Messages in this thread Patch in this message | | | Date | Sun, 29 May 2005 11:54:17 +0900 | From | Tejun Heo <> | Subject | [PATCH 2.6.12-rc5-mm1] CFQ: fix stall on force dispatch |
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Hello, Jens. Hello, Andrew.
The cfq-cfq-elevator_insert_back-fix.patch contains a bug which is triggered if force dispatching (back insertion) occurs when the active cfqq is in idle slice while there exist other requests on other cfqqs.
In this case, the idle slice timer is removed without invoking the timer handler, so CFQ itself doesn't run the queue. Also, as the queue wasn't empty when the elv_add_request() is invoked, the blk layer won't kick the queue on return. This results in queue stall.
This patch removes the stall by kicking the queue after force dispatching.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Index: blk-fixes/drivers/block/cfq-iosched.c =================================================================== --- blk-fixes.orig/drivers/block/cfq-iosched.c 2005-05-29 11:29:51.000000000 +0900 +++ blk-fixes/drivers/block/cfq-iosched.c 2005-05-29 11:29:54.000000000 +0900 @@ -1705,6 +1705,14 @@ cfq_insert_request(request_queue_t *q, s while (cfq_dispatch_requests(q, INT_MAX, 1)) ; list_add_tail(&rq->queuelist, &q->queue_head); + /* + * If we were idling with pending requests on + * inactive cfqqs, force dispatching will + * remove the idle timer and the queue won't + * be kicked by __make_request() afterward. + * Kick it here. + */ + kblockd_schedule_work(&cfqd->unplug_work); break; case ELEVATOR_INSERT_FRONT: list_add(&rq->queuelist, &q->queue_head); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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