From 0a0928d99a31240488c1f1e51cf424aa2ea3eacb Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 22 Jun 2011 19:47:02 +0200 Subject: block: Shorten interrupt disabled regions Moving the blk_sched_flush_plug() call out of the interrupt/preempt disabled region in the scheduler allows us to replace local_irq_save/restore(flags) by local_irq_disable/enable() in blk_flush_plug(). Now instead of doing this we disable interrupts explicitely when we lock the request_queue and reenable them when we drop the lock. That allows interrupts to be handled when the plug list contains requests for more than one queue. Aside of that this change makes the scope of the irq disabled region more obvious. The current code confused the hell out of me when looking at: local_irq_save(flags); spin_lock(q->queue_lock); ... queue_unplugged(q...); scsi_request_fn(); spin_unlock(q->queue_lock); spin_lock(shost->host_lock); spin_unlock_irq(shost->host_lock); -------------------^^^ ???? spin_lock_irq(q->queue_lock); spin_unlock(q->lock); local_irq_restore(flags); Also add a comment to __blk_run_queue() documenting that q->request_fn() can drop q->queue_lock and reenable interrupts, but must return with q->queue_lock held and interrupts disabled. Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: Tejun Heo Cc: Jens Axboe Cc: Linus Torvalds Link: http://lkml.kernel.org/r/20110622174919.025446432@linutronix.de Signed-off-by: Thomas Gleixner --- block/blk-core.c | 20 ++++++++------------ 1 file changed, 8 insertions(+), 12 deletions(-) (limited to 'block') diff --git a/block/blk-core.c b/block/blk-core.c index 15de223c7f93..7366ad422a5a 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -300,7 +300,11 @@ void __blk_run_queue(struct request_queue *q) { if (unlikely(blk_queue_stopped(q))) return; - + /* + * q->request_fn() can drop q->queue_lock and reenable + * interrupts, but must return with q->queue_lock held and + * interrupts disabled. + */ q->request_fn(q); } EXPORT_SYMBOL(__blk_run_queue); @@ -2745,11 +2749,11 @@ static void queue_unplugged(struct request_queue *q, unsigned int depth, * this lock). */ if (from_schedule) { - spin_unlock(q->queue_lock); + spin_unlock_irq(q->queue_lock); blk_run_queue_async(q); } else { __blk_run_queue(q); - spin_unlock(q->queue_lock); + spin_unlock_irq(q->queue_lock); } } @@ -2775,7 +2779,6 @@ static void flush_plug_callbacks(struct blk_plug *plug) void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule) { struct request_queue *q; - unsigned long flags; struct request *rq; LIST_HEAD(list); unsigned int depth; @@ -2796,11 +2799,6 @@ void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule) q = NULL; depth = 0; - /* - * Save and disable interrupts here, to avoid doing it for every - * queue lock we have to take. - */ - local_irq_save(flags); while (!list_empty(&list)) { rq = list_entry_rq(list.next); list_del_init(&rq->queuelist); @@ -2813,7 +2811,7 @@ void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule) queue_unplugged(q, depth, from_schedule); q = rq->q; depth = 0; - spin_lock(q->queue_lock); + spin_lock_irq(q->queue_lock); } /* * rq is already accounted, so use raw insert @@ -2831,8 +2829,6 @@ void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule) */ if (q) queue_unplugged(q, depth, from_schedule); - - local_irq_restore(flags); } void blk_finish_plug(struct blk_plug *plug) -- cgit v1.2.3