On 21/01/2021 23:28, Chris Wilson wrote:
The first thing the active retirement worker does is decrement the i915_active count.
The first thing we do during i915_active_wait is try to increment the i915_active count, but only if already active [non-zero].
The wait may see that the retirement is already started and so marked the i915_active as idle, and skip waiting for the retirement handler. However, the caller of i915_active_wait may immediately free the i915_active upon returning (e.g. i915_vma_destroy) so we must not return before the concurrent access from the worker are completed. We must always flush the worker.
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2473 Fixes: 274cbf20fd10 ("drm/i915: Push the i915_active.retire into a worker") Signed-off-by: Chris Wilson chris@chris-wilson.co.uk Cc: Matthew Auld matthew.auld@intel.com Cc: Tvrtko Ursulin tvrtko.ursulin@intel.com Cc: stable@vger.kernel.org # v5.5+
Reviewed-by: Matthew Auld matthew.auld@intel.com