119 lines
3.6 KiB
Diff
119 lines
3.6 KiB
Diff
From 7293618dd00ca6c13fac3d745c32a894687d62b4 Mon Sep 17 00:00:00 2001
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From: Thomas Gleixner <tglx@linutronix.de>
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Date: Wed, 22 Jun 2011 19:47:02 +0200
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Subject: [PATCH 006/303] block: Shorten interrupt disabled regions
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Moving the blk_sched_flush_plug() call out of the interrupt/preempt
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disabled region in the scheduler allows us to replace
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local_irq_save/restore(flags) by local_irq_disable/enable() in
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blk_flush_plug().
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Now instead of doing this we disable interrupts explicitely when we
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lock the request_queue and reenable them when we drop the lock. That
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allows interrupts to be handled when the plug list contains requests
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for more than one queue.
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Aside of that this change makes the scope of the irq disabled region
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more obvious. The current code confused the hell out of me when
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looking at:
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local_irq_save(flags);
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spin_lock(q->queue_lock);
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...
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queue_unplugged(q...);
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scsi_request_fn();
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spin_unlock(q->queue_lock);
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spin_lock(shost->host_lock);
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spin_unlock_irq(shost->host_lock);
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-------------------^^^ ????
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spin_lock_irq(q->queue_lock);
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spin_unlock(q->lock);
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local_irq_restore(flags);
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Also add a comment to __blk_run_queue() documenting that
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q->request_fn() can drop q->queue_lock and reenable interrupts, but
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must return with q->queue_lock held and interrupts disabled.
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Cc: Peter Zijlstra <peterz@infradead.org>
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Cc: Tejun Heo <tj@kernel.org>
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Cc: Jens Axboe <axboe@kernel.dk>
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Cc: Linus Torvalds <torvalds@linux-foundation.org>
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Link: http://lkml.kernel.org/r/20110622174919.025446432@linutronix.de
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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block/blk-core.c | 20 ++++++++------------
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1 file changed, 8 insertions(+), 12 deletions(-)
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diff --git a/block/blk-core.c b/block/blk-core.c
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index 49d9e91..33bf42c 100644
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--- a/block/blk-core.c
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+++ b/block/blk-core.c
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@@ -300,7 +300,11 @@ void __blk_run_queue(struct request_queue *q)
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{
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if (unlikely(blk_queue_stopped(q)))
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return;
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-
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+ /*
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+ * q->request_fn() can drop q->queue_lock and reenable
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+ * interrupts, but must return with q->queue_lock held and
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+ * interrupts disabled.
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+ */
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q->request_fn(q);
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}
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EXPORT_SYMBOL(__blk_run_queue);
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@@ -2745,11 +2749,11 @@ static void queue_unplugged(struct request_queue *q, unsigned int depth,
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* this lock).
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*/
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if (from_schedule) {
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- spin_unlock(q->queue_lock);
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+ spin_unlock_irq(q->queue_lock);
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blk_run_queue_async(q);
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} else {
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__blk_run_queue(q);
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- spin_unlock(q->queue_lock);
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+ spin_unlock_irq(q->queue_lock);
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}
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}
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@@ -2775,7 +2779,6 @@ static void flush_plug_callbacks(struct blk_plug *plug)
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void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
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{
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struct request_queue *q;
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- unsigned long flags;
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struct request *rq;
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LIST_HEAD(list);
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unsigned int depth;
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@@ -2796,11 +2799,6 @@ void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
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q = NULL;
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depth = 0;
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- /*
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- * Save and disable interrupts here, to avoid doing it for every
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- * queue lock we have to take.
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- */
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- local_irq_save(flags);
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while (!list_empty(&list)) {
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rq = list_entry_rq(list.next);
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list_del_init(&rq->queuelist);
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@@ -2813,7 +2811,7 @@ void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
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queue_unplugged(q, depth, from_schedule);
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q = rq->q;
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depth = 0;
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- spin_lock(q->queue_lock);
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+ spin_lock_irq(q->queue_lock);
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}
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/*
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* rq is already accounted, so use raw insert
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@@ -2831,8 +2829,6 @@ void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
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*/
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if (q)
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queue_unplugged(q, depth, from_schedule);
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-
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- local_irq_restore(flags);
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}
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void blk_finish_plug(struct blk_plug *plug)
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