linux-kernel - Block: Prevent busy looping

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Date:	Wed, 16 Apr 2008 17:37:48 +0200
From:	Elias Oltmanns <eo@...ensachen.de>
To:	Jens Axboe <jens.axboe@...cle.com>
Cc:	linux-kernel@...r.kernel.org, stable@...nel.org
Subject: Block: Prevent busy looping

blk_run_queue() as well as blk_start_queue() plug the device on reentry
and schedule blk_unplug_work() right afterwards. However,
blk_plug_device() takes care of that already and makes sure that there is
a short delay before blk_unplug_work() is scheduled. This is important
to prevent busy looping and possibly system lockups as observed here:
<http://permalink.gmane.org/gmane.linux.ide/28351>.

Signed-off-by: Elias Oltmanns <eo@...ensachen.de>
Cc: <stable@...nel.org>
---

 block/blk-core.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 2a438a9..e88a6f2 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -344,7 +344,6 @@ void blk_start_queue(struct request_queue *q)
 		clear_bit(QUEUE_FLAG_REENTER, &q->queue_flags);
 	} else {
 		blk_plug_device(q);
-		kblockd_schedule_work(&q->unplug_work);
 	}
 }
 EXPORT_SYMBOL(blk_start_queue);
@@ -412,7 +411,6 @@ void blk_run_queue(struct request_queue *q)
 			clear_bit(QUEUE_FLAG_REENTER, &q->queue_flags);
 		} else {
 			blk_plug_device(q);
-			kblockd_schedule_work(&q->unplug_work);
 		}
 	}
 


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