Revert "drm/i915: Don't skip request retirement if the active list is empty"

commit 245ec9d8 upstream.

This reverts commit 0aedb162.

I messed things up while applying [1] to drm-intel-fixes. Rectify.

[1] http://mid.gmane.org/1432827156-9605-1-git-send-email-ville.syrjala@linux.intel.com

Fixes: 0aedb162 ("drm/i915: Don't skip request retirement if the active list is empty")
Acked-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
[lizf: Backported to 3.4: adjust context]
Signed-off-by: Zefan Li <lizefan@huawei.com>

drivers/gpu/drm/i915/i915_gem.c

@@ -1779,6 +1779,9 @@ i915_gem_retire_requests_ring(struct intel_ring_buffer *ring)
 	uint32_t seqno;
 	int i;
 
+	if (list_empty(&ring->request_list))
+		return;
+
 	WARN_ON(i915_verify_lists(ring->dev));
 
 	seqno = ring->get_seqno(ring);