Commit d810583f authored by Chris Wilson's avatar Chris Wilson

drm/i915/execlists: Remove incorrect BUG_ON for schedule-out

As we may unwind incomplete requests (for preemption) prior to
processing the CSB and the schedule-out events, we may update rq->engine
(resetting it to point back to the parent virtual engine) prior to
calling execlists_schedule_out(), invalidating the assertion that the
request still points to the inflight engine. (The likelihood of this is
increased if the CSB interrupt processing is pushed to the ksoftirqd for
being too slow and direct submission overtakes it.)

Tvrtko summarised it as:
"So unwind from direct submission resets rq->engine and races with
process_csb from the tasklet which notices request has actually
completed."
Reported-by: default avatarVinay Belgaumkar <vinay.belgaumkar@intel.com>
Fixes: df403069 ("drm/i915/execlists: Lift process_csb() out of the irq-off spinlock")
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
Reviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190907105046.19934-1-chris@chris-wilson.co.uk
parent 5d7f965e
......@@ -631,7 +631,6 @@ execlists_schedule_out(struct i915_request *rq)
struct intel_engine_cs *cur, *old;
trace_i915_request_out(rq);
GEM_BUG_ON(intel_context_inflight(ce) != rq->engine);
old = READ_ONCE(ce->inflight);
do
......
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