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Date: Thu, 19 Jun 2014 08:15:42 +0200
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Subject: Re: [PATCH] drivers/i915: Fix unnoticed failure of init_ring_common()
From: Daniel Vetter <daniel.vetter@ffwll.ch>
To: Konrad Zapalowicz <bergo.torino@gmail.com>
Cc: "Nikula, Jani" <jani.nikula@linux.intel.com>,
        Dave Airlie <airlied@linux.ie>,
        intel-gfx <intel-gfx@lists.freedesktop.org>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Thu, Jun 19, 2014 at 12:38 AM, Konrad Zapalowicz
<bergo.torino@gmail.com> wrote:
> This commit add check for return value of init_ring_common() in the
> init_render_ring(). Now, when failure is detected the error code is
> propagated to the caller layer instead of being ignored.
>
> I believe that this fix will have a positive impact on the oops that
> I hit recently and which starts when init_ring_common() fails:
>
>     [drm:init_ring_common] *ERROR* render ring initialization failed
>              ctl 0001f001 head 0000000c tail 00000000 start 003eb000
>     BUG: unable to handle kernel NULL pointer dereference at 0000006c
>     IP: [<f8ca1679>] i915_gem_obj_to_ggtt+0x9/0x40 [i915]
>
> Signed-off-by: Konrad Zapalowicz <bergo.torino@gmail.com>

Do you have the full Oops somewhere?

> ---
>  drivers/gpu/drm/i915/intel_ringbuffer.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index 279488a..d205b0d 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -604,6 +604,8 @@ static int init_render_ring(struct intel_engine_cs *ring)
>         struct drm_device *dev = ring->dev;
>         struct drm_i915_private *dev_priv = dev->dev_private;
>         int ret = init_ring_common(ring);
> +       if (ret)
> +               return ret;

Yeah, on gen5+ this looks needed.
-Daniel

>
>         /* WaTimedSingleVertexDispatch:cl,bw,ctg,elk,ilk,snb */
>         if (INTEL_INFO(dev)->gen >= 4 && INTEL_INFO(dev)->gen < 7)
> --
> 1.8.1.2
>



-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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