linux-kernel - Re: [REGRESSION] commit 66c1ca0: {fbmem: fix fb_info->lock and mm->mmap

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Message-Id: <20090411112131.cc38dcf0.akpm@linux-foundation.org>
Date:	Sat, 11 Apr 2009 11:21:31 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Andrea Righi <righi.andrea@...il.com>
Cc:	Stefan Richter <stefanr@...6.in-berlin.de>,
	Krzysztof Helt <krzysztof.h1@...zta.fm>,
	Eric Miao <eric.y.miao@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Andrey Borzenkov <arvidjaar@...il.com>,
	"Antonino A. Daplas" <adaplas@...il.com>,
	linux-fbdev-devel@...ts.sourceforge.net,
	linux-pm@...ts.linux-foundation.org, Dave Jones <davej@...hat.com>,
	Harvey Harrison <harvey.harrison@...il.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Pavel Roskin <proski@....org>
Subject: Re: [REGRESSION] commit 66c1ca0: {fbmem: fix fb_info->lock and
 mm->mmap_sem ...} causes Xfbdev not working

On Sat, 11 Apr 2009 17:04:00 +0200 Andrea Righi <righi.andrea@...il.com> wrote:

> fbdev: fix info->lock deadlock in fbcon_event_notify()
> 
> fb_notifier_call_chain() is called with info->lock held, i.e. in
> do_fb_ioctl() => FBIOPUT_VSCREENINFO => fb_set_var() and the some
> notifier callbacks, like fbcon_event_notify(), try to re-acquire
> info->lock again.
> 
> Remove the lock/unlock_fb_info() in all the framebuffer notifier
> callbacks' and be sure to always call fb_notifier_call_chain() with
> info->lock held.

Thanks.  So do you think we should proceed with this patch instead of
reverting 66c1ca0?
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