linux-kernel - Re: Deadlock between fbcon and fb

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Message-ID: <AANLkTik0EkPYKdnhrpF7yK6eXIrHMsNYrzSC6tyeBR0P@mail.gmail.com>
Date:	Mon, 10 May 2010 08:00:51 +0800
From:	Jaya Kumar <jayakumar.lkml@...il.com>
To:	Bruno Prémont <bonbons@...ux-vserver.org>
Cc:	linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Jiri Kosina <jkosina@...e.cz>
Subject: Re: Deadlock between fbcon and fb_defio?

On Mon, May 10, 2010 at 12:49 AM, Bruno Prémont
<bonbons@...ux-vserver.org> wrote:
>
> Fix crash if we are the first framebuffer loaded as in that case fbcon
> wants to flush framebuffer at the end of fb registration, before we
> have setup fb_defio.

Bruno,

Please help me understand, how does this scenario occur? I'm
interpreting what you've written above to mean that fbcon is accessing
the framebuffer before you've called defio_init()? Is that correct?

The typical defio use sequence is: defio_init(),
register_framebuffer() and the typical remove sequence is in the
reverse order unregister_framebuffer(), defio_cleanup(). So, I don't
see how fbcon is accessing the framebuffer either before
register_framebuffer() completes (at which point defio init is already
done) or after unregister_framebuffer() completes.

Thanks,
jaya
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