From 80a4b58e36b63d7b0b592beb1bd6410aadeeb63c Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Tue, 14 Oct 2008 09:51:06 +0200 Subject: block: only call ->request_fn when the queue is not stopped Callers should use either blk_run_queue/__blk_run_queue, or blk_start_queueing() to invoke request handling instead of calling ->request_fn() directly as that does not take the queue stopped flag into account. Also add appropriate comments on the above functions to detail their usage. Signed-off-by: Jens Axboe --- block/blk-core.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) (limited to 'block/blk-core.c') diff --git a/block/blk-core.c b/block/blk-core.c index 2d053b58441..91532f2d2fa 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -325,6 +325,9 @@ EXPORT_SYMBOL(blk_unplug); static void blk_invoke_request_fn(struct request_queue *q) { + if (unlikely(blk_queue_stopped(q))) + return; + /* * one level of recursion is ok and is much faster than kicking * the unplug handling @@ -399,8 +402,13 @@ void blk_sync_queue(struct request_queue *q) EXPORT_SYMBOL(blk_sync_queue); /** - * blk_run_queue - run a single device queue + * __blk_run_queue - run a single device queue * @q: The queue to run + * + * Description: + * See @blk_run_queue. This variant must be called with the queue lock + * held and interrupts disabled. + * */ void __blk_run_queue(struct request_queue *q) { @@ -418,6 +426,12 @@ EXPORT_SYMBOL(__blk_run_queue); /** * blk_run_queue - run a single device queue * @q: The queue to run + * + * Description: + * Invoke request handling on this queue, if it has pending work to do. + * May be used to restart queueing when a request has completed. Also + * See @blk_start_queueing. + * */ void blk_run_queue(struct request_queue *q) { @@ -884,7 +898,8 @@ EXPORT_SYMBOL(blk_get_request); * * This is basically a helper to remove the need to know whether a queue * is plugged or not if someone just wants to initiate dispatch of requests - * for this queue. + * for this queue. Should be used to start queueing on a device outside + * of ->request_fn() context. Also see @blk_run_queue. * * The queue lock must be held with interrupts disabled. */ -- cgit v1.2.3-18-g5258