On Thu, Mar 16, 2017 at 02:53:05PM +0000, Chris Wilson wrote:
> Do an early read of the execlists' queue before we take the spinlock and
> start checking. This is safe as the first writer to the execlists queue
> will cause the tasklet to be run again after a memory barrier.
> 
> Signed-off-by: Chris Wilson <[email protected]>
> Cc: Tvrtko Ursulin <[email protected]>
> Cc: Joonas Lahtinen <[email protected]>
> Cc: Michał Winiarski <[email protected]>
> ---
> 
> With the plan to kick the tasklet before it is ready, eliminating a few
> of the heavier checks seems sensible.
> -Chris

Now that we're also driving GuC submission in a similar way, this patch should
also include similar early read for guc dequeue.

With that:
Reviewed-by: Michał Winiarski <[email protected]>

-Michał

> 
> ---
>  drivers/gpu/drm/i915/intel_lrc.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c 
> b/drivers/gpu/drm/i915/intel_lrc.c
> index 89f38e7def9f..17342bc939ad 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -402,6 +402,9 @@ static void execlists_dequeue(struct intel_engine_cs 
> *engine)
>       struct rb_node *rb;
>       bool submit = false;
>  
> +     if (!READ_ONCE(engine->execlist_first))
> +             return;
> +
>       last = port->request;
>       if (last)
>               /* WaIdleLiteRestore:bdw,skl
> -- 
> 2.11.0
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