Re: [Intel-gfx] [PATCH 12/22] drm/i915/execlists: Check the sentinel is alone in the ELSP

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> We only use sentinel requests for "preempt-to-idle" passes, so assert
> that they are the only request in a new submission.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

From other thread,

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

> ---
>  drivers/gpu/drm/i915/gt/intel_lrc.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> index 15d56cd3937e..b9b3f78f1324 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -1448,6 +1448,7 @@ assert_pending_valid(const struct intel_engine_execlists *execlists,
>  {
>  	struct i915_request * const *port, *rq;
>  	struct intel_context *ce = NULL;
> +	bool sentinel = false;
>  
>  	trace_ports(execlists, msg, execlists->pending);
>  
> @@ -1481,6 +1482,26 @@ assert_pending_valid(const struct intel_engine_execlists *execlists,
>  		}
>  		ce = rq->context;
>  
> +		/*
> +		 * Sentinels are supposed to be lonely so they flush the
> +		 * current exection off the HW. Check that they are the
> +		 * only request in the pending submission.
> +		 */
> +		if (sentinel) {
> +			GEM_TRACE_ERR("context:%llx after sentinel in pending[%zd]\n",
> +				      ce->timeline->fence_context,
> +				      port - execlists->pending);
> +			return false;
> +		}
> +
> +		sentinel = i915_request_has_sentinel(rq);
> +		if (sentinel && port != execlists->pending) {
> +			GEM_TRACE_ERR("sentinel context:%llx not in prime position[%zd]\n",
> +				      ce->timeline->fence_context,
> +				      port - execlists->pending);
> +			return false;
> +		}
> +
>  		/* Hold tightly onto the lock to prevent concurrent retires! */
>  		if (!spin_trylock_irqsave(&rq->lock, flags))
>  			continue;
> -- 
> 2.25.1
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