[Intel-gfx] [PATCH v3 06/10] drm/fb-helper: Support deferred setup

[Thierry Reding]

On Tue, Mar 21, 2017 at 11:10:22AM +0100, Daniel Vetter wrote:
> On Tue, Mar 21, 2017 at 09:13:54AM +0100, Thierry Reding wrote:
[...]
> > diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
[...]
> > @@ -2437,11 +2476,16 @@ EXPORT_SYMBOL(drm_fb_helper_initial_config);
> >  int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper)
> >  {
> >  	struct drm_device *dev = fb_helper->dev;
> > +	unsigned int width, height;
> >  	int err = 0;
> >  
> >  	if (!drm_fbdev_emulation)
> >  		return 0;
> >  
> > +	if (fb_helper->deferred_setup)
> > +		return drm_fb_helper_initial_config(fb_helper,
> > +						    fb_helper->preferred_bpp);
> 
> I think this must be moved under the protection of ->lock, you might race
> otherwise (e.g. hpd vs. userspace forcing a re-probe, both noticing the
> change).

I think I had originally put this under the lock only to see that result
in a deadlock. I can't quite remember why that was, but testing shows
that this still happens. It's getting rather late, so I'll have to defer
tracking this down to tomorrow.

Thierry
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