linux-kernel - Re: [PATCH] mmc: prevent dangling block device from accessing stale queues

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Message-ID: <4A281F33.80606@canonical.com>
Date:	Thu, 04 Jun 2009 21:23:31 +0200
From:	Stefan Bader <stefan.bader@...onical.com>
To:	Matt Fleming <matt@...sole-pimps.org>
CC:	Pierre Ossman <pierre@...man.eu>, Jens Axboe <axboe@...nel.dk>,
	linux-kernel@...r.kernel.org, Andy Whitcroft <apw@...onical.com>
Subject: Re: [PATCH] mmc: prevent dangling block device from accessing	stale
 queues

Matt Fleming wrote:
> On Thu, Jun 04, 2009 at 09:00:42PM +0200, Stefan Bader wrote:
>> Hm, not sure this is what you wanted to know... On the launchpad report 
>> there are logs which I took with lots of printk's enabled. This shows that 
>> after resume the queue receives a request from mmcblk0 (which no longer 
>> exists) but uses the same pointer as mmcblk1 which was just created.
>>
> 
> Maybe I'm missing something, but why is the device instance being
> destroyed during a suspend? E.g why do you have mmcblk0 before suspend and
> mmcblk1 after suspend?

That is the way mmcblock works  (without unsafe resume set) in conjunction with 
( probably ) slow userspace. On suspend the block device is removed. But the 
mount is cleaned by (in that case hald) doing a forced unmount. The timeing 
seems to be that the unmount part is partially done on the way up.

-- 

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