drm/i915: Integrate i915_sw_fence with debugobjects

Add the tracking required to enable debugobjects for fences to improve
error detection in BAT. The debugobject interface lets us track the
lifetime and phases of the fences even while being embedded into larger
structs, i.e. to check they are not used after they have been released.

v2: Don't populate the stubs, debugobjects checks for a NULL pointer and
treats it equivalently.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161125131718.20978-4-chris@chris-wilson.co.uk

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index 94d71b639f12..fcf22b0e2967 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -62,6 +62,15 @@ static void i915_fence_release(struct dma_fence *fence)
 {
 	struct drm_i915_gem_request *req = to_request(fence);
 
+	/* The request is put onto a RCU freelist (i.e. the address
+	 * is immediately reused), mark the fences as being freed now.
+	 * Otherwise the debugobjects for the fences are only marked as
+	 * freed when the slab cache itself is freed, and so we would get
+	 * caught trying to reuse dead objects.
+	 */
+	i915_sw_fence_fini(&req->submit);
+	i915_sw_fence_fini(&req->execute);
+
 	kmem_cache_free(req->i915->requests, req);
 }