Re: [Intel-gfx] [PATCH] drm/i915/gt: Drop active.lock around active request read inside execlists

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

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

> As we find the active request for capturing upon a hang, we know that the
> lists are stable as we are inside the execlists tasklet, the only path
> that can modify those lists. As such, we do not need to disable irqs and
> take the active lock for a simple read of the current request.
>
> Suggested-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>

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

> ---
>  drivers/gpu/drm/i915/gt/intel_execlists_submission.c | 2 --
>  1 file changed, 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> index b5f2459cac2c..e20ab2eab3a8 100644
> --- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> +++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> @@ -2262,13 +2262,11 @@ static void execlists_capture(struct intel_engine_cs *engine)
>  	if (!cap)
>  		return;
>  
> -	spin_lock_irq(&engine->active.lock);
>  	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);
>  	}
> -	spin_unlock_irq(&engine->active.lock);
>  	if (!cap->rq)
>  		goto err_free;
>  
> -- 
> 2.20.1
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