[Intel-gfx] [PATCH] drm/i915: WARN if the fence pin_count is invalid

[Chris Wilson]

Stéphane Marchesin found a bug where the fences were not being restored,
and in particular the fence pin_count was incorrect. Had we had a
warning in place, this bug would have come to light much earlier. Better
late than never?

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Stéphane Marchesin <marcheu at chromium.org>
---
 drivers/gpu/drm/i915/i915_drv.h |    1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 1a67216..041091d 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1722,6 +1722,7 @@ i915_gem_object_unpin_fence(struct drm_i915_gem_object *obj)
 {
 	if (obj->fence_reg != I915_FENCE_REG_NONE) {
 		struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
+		WARN_ON(dev_priv->fence_regs[obj->fence_reg].pin_count <= 0);
 		dev_priv->fence_regs[obj->fence_reg].pin_count--;
 	}
 }
-- 
1.7.10.4