drm/i915: Hold a ref to the ring while retiring

As the final request on a ring may hold the reference to this ring (via
retiring the last pinned context), we may find ourselves chasing a
dangling pointer on completion of the list.

A quick solution is to hold a reference to the ring itself as we retire
along it so that we only free it after we stop dereferencing it.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190318095204.9913-4-chris@chris-wilson.co.uk

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/selftests/mock_engine.c b/drivers/gpu/drm/i915/selftests/mock_engine.c
index f6d120e05ee4..881450c694e9 100644
--- a/drivers/gpu/drm/i915/selftests/mock_engine.c
+++ b/drivers/gpu/drm/i915/selftests/mock_engine.c
@@ -57,6 +57,7 @@ static struct intel_ring *mock_ring(struct intel_engine_cs *engine)
 		return NULL;
 	}
 
+	kref_init(&ring->base.ref);
 	ring->base.size = sz;
 	ring->base.effective_size = sz;
 	ring->base.vaddr = (void *)(ring + 1);