Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
> Since commit 22b7a426bbe1 ("drm/i915/execlists: Preempt-to-busy"), we
> prune the engine->active.requests list prior to preemption, thus
> removing the trace of the currently executing request. If that request
> hangs rather than be preempted, we conclude that no active request was
> on the GPU. Fortunately, this only impacts our debugging, and not our
> means of hang detection or recovery.
>
> v2: Use from to check the current iterator before continuing, and report
> active as NULL if the current request is already completed.
>
> References: 22b7a426bbe1 ("drm/i915/execlists: Preempt-to-busy")
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
Reviewed-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/gt/intel_engine_cs.c | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> index 06ff7695fa29..2d0ef5fc6748 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> @@ -1657,6 +1657,23 @@ intel_engine_find_active_request(struct intel_engine_cs *engine)
> * we only care about the snapshot of this moment.
> */
> lockdep_assert_held(&engine->active.lock);
> +
> + rcu_read_lock();
> + request = execlists_active(&engine->execlists);
> + if (request) {
> + struct intel_timeline *tl = request->context->timeline;
> +
> + list_for_each_entry_from_reverse(request, &tl->requests, link) {
> + if (i915_request_completed(request))
> + break;
> +
> + active = request;
> + }
> + }
> + rcu_read_unlock();
> + if (active)
> + return active;
> +
> list_for_each_entry(request, &engine->active.requests, sched.link) {
> if (i915_request_completed(request))
> continue;
> --
> 2.25.0
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