[Intel-gfx] [PATCH] drm/i915/gt: Report the currently active execlists request

[Mika Kuoppala]

Chris Wilson <chris at chris-wilson.co.uk> 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 at chris-wilson.co.uk>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>

Reviewed-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>

> ---
>  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