Re: Possible deadlock when suspending framebuffer

[Florian Tobias Schandinat]

Hi Linus,

On 06/14/2011 06:15 PM, Linus Torvalds wrote:
> Paul, fbdev people.. Comments? This was sent to me and lkml, the right
> people probably didn't see it.

Sounds very familiar. Indeed a quick glance at my archive revealed 2 
approaches/patches dealing with similar issues
http://marc.info/?l=linux-fbdev&m=129539210207429&w=2
http://marc.info/?l=linux-fbdev&m=129700789632450&w=2

I did not have time to verify that those do actually get those things right 
everywhere but the first one looks good and should also solve this issue I think.


Regards,

Florian Tobias Schandinat

> I doubt it's a big problem in practice, but..
>
>                        Linus
>
> On Tue, Jun 14, 2011 at 6:10 AM, Francis Moreau<francis.moro@xxxxxxxxx>  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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