[Intel-gfx] [PATCH] drm/i915: Move assert of page pin vs bind count into i915_vma_unbind

[Chris Wilson]

The read of the page pin count and the bind count are unordered,
presenting races in the assert and it firing off incorrectly. Prevent
this by restricting the assert to the vma bind/unbind routines where we
have local cpu ordering between the two.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
---
 drivers/gpu/drm/i915/i915_drv.h | 1 -
 drivers/gpu/drm/i915/i915_vma.c | 1 +
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 00ecbb4da25e..1aa33444115a 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3291,7 +3291,6 @@ __i915_gem_object_unpin_pages(struct drm_i915_gem_object *obj)
 	GEM_BUG_ON(!obj->mm.pages);
 
 	atomic_dec(&obj->mm.pages_pin_count);
-	GEM_BUG_ON(atomic_read(&obj->mm.pages_pin_count) < obj->bind_count);
 }
 
 static inline void
diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index 414f0f7f5059..d48c68214611 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -640,6 +640,7 @@ int i915_vma_unbind(struct i915_vma *vma)
 	 * reaped by the shrinker.
 	 */
 	i915_gem_object_unpin_pages(obj);
+	GEM_BUG_ON(atomic_read(&obj->mm.pages_pin_count) < obj->bind_count);
 
 destroy:
 	if (unlikely(i915_vma_is_closed(vma)))
-- 
2.11.0