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

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Message-ID: <5270EB85.1030103@ti.com>
Date:	Wed, 30 Oct 2013 13:20:37 +0200
From:	Tomi Valkeinen <tomi.valkeinen@...com>
To:	Gu Zheng <guz.fnst@...fujitsu.com>,
	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>
CC:	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,

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.

 Tomi



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