Re: [PATCH v2 3/3] drm/i915: Only wake the waiter from the interrupt if passed

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

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

> As we now check if the seqno is complete in order to signal the fence,
> we can also decide not to wake up the first_waiter until it is ready
> (since it is waiting on the same seqno). The only caveat is that if we
> need the engine->irq_seqno_barrier to enforce some coherency between an
> interrupt and the seqno read, we have to always wake the waiter into to
> perform that heavyweight barrier.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/i915_irq.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index 3f39e36fa566..c902aff61a9d 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -1059,7 +1059,8 @@ static void notify_ring(struct intel_engine_cs *engine)
>  				      wait->seqno))
>  			rq = wait->request;
>
> -		wake_up_process(wait->tsk);
> +		if (rq || engine->irq_seqno_barrier)
> +			wake_up_process(wait->tsk);

This also needs to be respinned on top of getting the request ref.

Were you thinking < gen5 or daydreaming that the next shiny one doesn't
need a barrier? :)

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

>  	} else {
>  		__intel_engine_disarm_breadcrumbs(engine);
>  	}
> -- 
> 2.11.0
>
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