Re: [ 109/173] drm/i915: Close race between processing unpin taskand queueing the flip

[Herton Ronaldo Krzesinski]

On Fri, Dec 28, 2012 at 08:05:19PM +0100, Ben Hutchings wrote:
> 3.2-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> 
> commit e7d841ca03b7ab668620045cd7b428eda9f41601 upstream.
> 
[...]
> @@ -7157,6 +7176,10 @@ static int intel_gen4_queue_flip(struct
>  	pf = 0;
>  	pipesrc = I915_READ(PIPESRC(intel_crtc->pipe)) & 0x0fff0fff;
>  	OUT_RING(pf | pipesrc);
> +
> +	intel_mark_page_flip_active(intel_crtc);
> +
> +	intel_mark_page_flip_active(intel_crtc);
>  	ADVANCE_LP_RING();
>  	return 0;
>  

There is a problem with this patch on 3.2. First we have
intel_mark_page_flip_active duplicated on intel_gen4_queue_flip here
(harmless), but one missing call for it in intel_gen6_queue_flip

Reached to this after reproducing which is probably the same
problem people are reporting here: http://bugs.launchpad.net/bugs/1119809
A bisect pointed to this change, and the following diff fixed the issue
on the i915 based machine I used to reproduce:

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 4da3c7e..ce23961 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -7155,8 +7155,6 @@ static int intel_gen4_queue_flip(struct drm_device *dev,
 	OUT_RING(pf | pipesrc);
 
 	intel_mark_page_flip_active(intel_crtc);
-
-	intel_mark_page_flip_active(intel_crtc);
 	ADVANCE_LP_RING();
 	return 0;
 
@@ -7192,6 +7190,8 @@ static int intel_gen6_queue_flip(struct drm_device *dev,
 	pf = I915_READ(PF_CTL(intel_crtc->pipe)) & PF_ENABLE;
 	pipesrc = I915_READ(PIPESRC(intel_crtc->pipe)) & 0x0fff0fff;
 	OUT_RING(pf | pipesrc);
+
+	intel_mark_page_flip_active(intel_crtc);
 	ADVANCE_LP_RING();
 	return 0;
 

-- 
[]'s
Herton
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