linux-kernel - Re: Possible deadlock when suspending framebuffer

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Message-ID: <BANLkTimny9nzr23TufH1kMcsk57M3NXuaA@mail.gmail.com>
Date:	Tue, 14 Jun 2011 11:15:53 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Paul Mundt <lethal@...ux-sh.org>, linux-fbdev@...r.kernel.org
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Francis Moreau <francis.moro@...il.com>
Subject: Re: Possible deadlock when suspending framebuffer

Paul, fbdev people.. Comments? This was sent to me and lkml, the right
people probably didn't see it.

I doubt it's a big problem in practice, but..

                      Linus

On Tue, Jun 14, 2011 at 6:10 AM, Francis Moreau <francis.moro@...il.com> wrote:
> Hello,
>
> I noticed that a possible deadlock can happen when the current frame
> buffering is being suspended and a new frambuffer device is being
> registred at the same time.
>
> When suspending the current frambuffer by doing : echo 1
>>/sys/class/graphics/fb0/state, the kernel actually takes the
> following locks in that order: console_lock, lock_fb_info (see
> store_fbstate()).
>
> However when a new framebuffer is coming in, the lock sequence is:
> lock_fb_info (taken by do_remove_conflicting_framebuffer()),
> console_lock() (taken by unbind_console).
>
> I don't know how this should be fixed though...
>
> Thanks
> --
> Francis
>
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