linux-kernel - Re: [RFC PATCH RESEND] fb: reorder the lock sequence to fix a potential lockdep

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Date:	Thu, 31 Oct 2013 09:17:05 +0800
From:	Gu Zheng <guz.fnst@...fujitsu.com>
To:	Tomi Valkeinen <tomi.valkeinen@...com>
CC:	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH RESEND] fb: reorder the lock sequence to fix a potential
 lockdep

Hi Tomi,

On 10/30/2013 07:20 PM, Tomi Valkeinen wrote:

> Hi,
> 
> On 2013-10-28 08:01, Gu Zheng wrote:
>> Following commits:
>> 50e244cc79 fb: rework locking to fix lock ordering on takeover
>> e93a9a8687 fb: Yet another band-aid for fixing lockdep mess
>> 054430e773 fbcon: fix locking harder
>>
>> reworked locking to fix related lock ordering on takeover, and introduced console_lock
>> into fbmem, but it seems that the new lock sequence(fb_info->lock ---> console_lock)
>> is against with the one in console_callback(console_lock ---> fb_info->lock), and leads to
>> a potential deadlock as following:
> 
> A quick grep shows that there are other places than fbmem.c which use
> lock_fb_info and console_lock, for example drivers/video/sh_mobile_lcdcfb.c.

Yes, thanks for your reminder, I'll fix them all in the next version.

Regards,
Gu

> 
>  Tomi
> 
> 


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