linux-kernel - Re: [BUG] Problem since "block: make gendisk hold a reference to its queue"

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Date:	Tue, 10 Jan 2012 08:22:34 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Dirk Gouders <gouders@...bocholt.fh-gelsenkirchen.de>
Cc:	Kay Sievers <kay.sievers@...y.org>, linux-kernel@...r.kernel.org
Subject: Re: [BUG] Problem since "block: make gendisk hold a reference to
 its queue"

Hello,

On Tue, Jan 10, 2012 at 03:11:10PM +0100, Dirk Gouders wrote:
> I noticed problematic kernel messages when my laptop boots, bisecting
> this issue lead me to commit 523e1d399c.  I attach the messages that I
> currently (commit e4e11180df) see, please let me know if further
> information is needed.

Thank you very much for bisecting the problem.

> floppy0: no floppy controllers found
> =============================================================================
> BUG blkdev_queue: Poison overwritten
> -----------------------------------------------------------------------------

Yeah, floppy does some funky stuff during init.

> Object ffff88006ec30420: 6b 6b 6b 6b 6b 6b 6b 6b 6a 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkjkkkkkkk

This looks like refcnt is dec'd after released.  Can you please apply
the following patch and see whether the WARN_ON() triggers?

diff --git a/block/blk-core.c b/block/blk-core.c
index 15de223..c3de15e 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -342,6 +342,7 @@ EXPORT_SYMBOL(blk_run_queue);
 
 void blk_put_queue(struct request_queue *q)
 {
+	WARN_ON(atomic_read(&q->kobj.kref.refcount) == 0x6b6b6b6b);
 	kobject_put(&q->kobj);
 }
 EXPORT_SYMBOL(blk_put_queue);
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