linux-kernel - Re: [regression] Re: 4.11-rc0, thinkpad x220: GPU hang

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Message-ID: <20170306122341.GA3201@nuc-i3427.alporthouse.com>
Date:   Mon, 6 Mar 2017 12:23:41 +0000
From:   Chris Wilson <chris@...is-wilson.co.uk>
To:     Pavel Machek <pavel@....cz>
Cc:     kernel list <linux-kernel@...r.kernel.org>,
        daniel.vetter@...el.com, jani.nikula@...ux.intel.com,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org
Subject: Re: [regression] Re: 4.11-rc0, thinkpad x220: GPU hang

On Mon, Mar 06, 2017 at 01:10:48PM +0100, Pavel Machek wrote:
> On Mon 2017-03-06 11:15:28, Chris Wilson wrote:
> > On Mon, Mar 06, 2017 at 12:01:51AM +0100, Pavel Machek wrote:
> > > Hi!
> > > 
> > > > > mplayer stopped working after a while. Dmesg says:
> > > > > 
> > > > > [ 3000.266533] cdc_ether 2-1.2:1.0 usb0: register 'cdc_ether' at
> > > 
> > > Now I'm pretty sure it is a regression in v4.11-rc0. Any ideas what to
> > > try? Bisect will be slow and nasty :-(.
> > 
> > I came the conclusion that #99671 is the ring HEAD overtaking the TAIL,
> > and under the presumption that your bug matches (as the symptoms do):
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> > index 4ffa35faff49..62e31a7438ac 100644
> > --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> > +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> > @@ -782,10 +782,10 @@ static void i9xx_submit_request(struct drm_i915_gem_request *request)
> >  {
> >         struct drm_i915_private *dev_priv = request->i915;
> >  
> > -       i915_gem_request_submit(request);
> > -
> >         GEM_BUG_ON(!IS_ALIGNED(request->tail, 8));
> >         I915_WRITE_TAIL(request->engine, request->tail);
> > +
> > +       i915_gem_request_submit(request);
> >  }
> >  
> >  static void i9xx_emit_breadcrumb(struct drm_i915_gem_request *req, u32 *cs)
> 
> I applied it as:
> 
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index 91bc4ab..9c49c7a 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -1338,9 +1338,9 @@ static void i9xx_submit_request(struct drm_i915_gem_request *request)
>  {
>  	struct drm_i915_private *dev_priv = request->i915;
>  
> -	i915_gem_request_submit(request);
> -
>  	I915_WRITE_TAIL(request->engine, request->tail);
> +
> +	i915_gem_request_submit(request);
>  }
>  
>  static void i9xx_emit_breadcrumb(struct drm_i915_gem_request *req,
> 
> Hmm. But your next mail suggest that it may not be smart to try to
> boot it? :-).

Don't bother, it'll promptly hang.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre