Re: [Intel-gfx] [PATCH 1/2] drm/i915/execlists: Peek at the next submission for error interrupts

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

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

> If we receive the error interrupt before the CS interrupt, we may find
> ourselves without an active request to reset, skipping the GPU reset.
> All because the attempt to reset was too early.
>

With the tracing, we will see the the out of sync situations
so

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


> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/gt/intel_lrc.c | 41 ++++++++++++++++++++++++++++-
>  1 file changed, 40 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> index 3479cda37fdc..f028114714cd 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -2804,6 +2804,45 @@ static struct execlists_capture *capture_regs(struct intel_engine_cs *engine)
>  	return NULL;
>  }
>  
> +static struct i915_request *
> +active_context(struct intel_engine_cs *engine, u32 ccid)
> +{
> +	const struct intel_engine_execlists * const el = &engine->execlists;
> +	struct i915_request * const *port, *rq;
> +
> +	/*
> +	 * Use the most recent result from process_csb(), but just in case
> +	 * we trigger an error (via interrupt) before the first CS event has
> +	 * been written, peek at the next submission.
> +	 */
> +
> +	for (port = el->active; (rq = *port); port++) {
> +		if (upper_32_bits(rq->context->lrc_desc) == ccid) {
> +			ENGINE_TRACE(engine,
> +				     "ccid found at active:%zd\n",
> +				     port - el->active);
> +			return rq;
> +		}
> +	}
> +
> +	for (port = el->pending; (rq = *port); port++) {
> +		if (upper_32_bits(rq->context->lrc_desc) == ccid) {
> +			ENGINE_TRACE(engine,
> +				     "ccid found at pending:%zd\n",
> +				     port - el->pending);
> +			return rq;
> +		}
> +	}
> +
> +	ENGINE_TRACE(engine, "ccid:%x not found\n", ccid);
> +	return NULL;
> +}
> +
> +static u32 active_ccid(struct intel_engine_cs *engine)
> +{
> +	return ENGINE_READ_FW(engine, RING_EXECLIST_STATUS_HI);
> +}
> +
>  static bool execlists_capture(struct intel_engine_cs *engine)
>  {
>  	struct execlists_capture *cap;
> @@ -2821,7 +2860,7 @@ static bool execlists_capture(struct intel_engine_cs *engine)
>  		return true;
>  
>  	spin_lock_irq(&engine->active.lock);
> -	cap->rq = execlists_active(&engine->execlists);
> +	cap->rq = active_context(engine, active_ccid(engine));
>  	if (cap->rq) {
>  		cap->rq = active_request(cap->rq->context->timeline, cap->rq);
>  		cap->rq = i915_request_get_rcu(cap->rq);
> -- 
> 2.20.1
>
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