linux-kernel - [PATCH] drivers/i915: Fix unnoticed failure of init_ring

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Message-Id: <1403131134-9533-1-git-send-email-bergo.torino@gmail.com>
Date:	Thu, 19 Jun 2014 00:38:54 +0200
From:	Konrad Zapalowicz <bergo.torino@...il.com>
To:	daniel.vetter@...ll.ch
Cc:	jani.nikula@...ux.intel.com, airlied@...ux.ie,
	intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	Konrad Zapalowicz <bergo.torino@...il.com>
Subject: [PATCH] drivers/i915: Fix unnoticed failure of init_ring_common()

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

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