[PATCH] drm/i915: Kill dangerous pending-flip debugging

[PATCH] drm/i915: Kill dangerous pending-flip debugging

[Chris Wilson]

We can, by virtue of a vblank interrupt firing in the middle of setting
up the unpin work (i.e. after we set the unpin_work field and before we
write to the ringbuffer) enter intel_finish_page_flip() prior to
receiving the pending flip notification. Therefore we can expect to hit
intel_finish_page_flip() under normal circumstances without a pending flip
and even without installing the pending_flip_obj. This is exacerbated by
aperture thrashing whilst binding the framebuffer

References:

  Bug 28079 - "glresize" causes kernel panic in intel_finish_page_flip.
  https://bugs.freedesktop.org/show_bug.cgi?id=28079

Reported-by: Nick Bowler <nbowler@draconx.ca>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: stable@kernel.org
---
 drivers/gpu/drm/i915/intel_display.c |    6 ------
 1 files changed, 0 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 77d8732..35937ce 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -4155,12 +4155,6 @@ void intel_finish_page_flip(struct drm_device *dev, int pipe)
 	spin_lock_irqsave(&dev->event_lock, flags);
 	work = intel_crtc->unpin_work;
 	if (work == NULL || !work->pending) {
-		if (work && !work->pending) {
-			obj_priv = to_intel_bo(work->pending_flip_obj);
-			DRM_DEBUG_DRIVER("flip finish: %p (%d) not pending?\n",
-					 obj_priv,
-					 atomic_read(&obj_priv->pending_flip));
-		}
 		spin_unlock_irqrestore(&dev->event_lock, flags);
 		return;
 	}
-- 
1.7.1

Re: [PATCH] drm/i915: Kill dangerous pending-flip debugging

[Jesse Barnes]

On Sat, 15 May 2010 09:57:03 +0100
Chris Wilson <chris@chris-wilson.co.uk> wrote:

> We can, by virtue of a vblank interrupt firing in the middle of
> setting up the unpin work (i.e. after we set the unpin_work field and
> before we write to the ringbuffer) enter intel_finish_page_flip()
> prior to receiving the pending flip notification. Therefore we can
> expect to hit intel_finish_page_flip() under normal circumstances
> without a pending flip and even without installing the
> pending_flip_obj. This is exacerbated by aperture thrashing whilst
> binding the framebuffer
> 
> References:
> 
>   Bug 28079 - "glresize" causes kernel panic in
> intel_finish_page_flip.
> https://bugs.freedesktop.org/show_bug.cgi?id=28079

Yeah, that's true.  Good catch.

Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>

Re: [PATCH] drm/i915: Kill dangerous pending-flip debugging

[Eric Anholt]

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On Sat, 15 May 2010 09:31:17 -0700, Jesse Barnes <jbarnes@virtuousgeek.org> wrote:
> On Sat, 15 May 2010 09:57:03 +0100
> Chris Wilson <chris@chris-wilson.co.uk> wrote:
> 
> > We can, by virtue of a vblank interrupt firing in the middle of
> > setting up the unpin work (i.e. after we set the unpin_work field and
> > before we write to the ringbuffer) enter intel_finish_page_flip()
> > prior to receiving the pending flip notification. Therefore we can
> > expect to hit intel_finish_page_flip() under normal circumstances
> > without a pending flip and even without installing the
> > pending_flip_obj. This is exacerbated by aperture thrashing whilst
> > binding the framebuffer
> > 
> > References:
> > 
> >   Bug 28079 - "glresize" causes kernel panic in
> > intel_finish_page_flip.
> > https://bugs.freedesktop.org/show_bug.cgi?id=28079
> 
> Yeah, that's true.  Good catch.
> 
> Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>

Applied.  Thanks!

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