[Intel-gfx] [PATCH i-g-t] i915/gem_ctx_engine: Prevent preemption

[Tvrtko Ursulin]

On 18/06/2019 21:21, Chris Wilson wrote:
> In order to pin the engine as busy, we have to prevent the kernel from
> executing other independent work ahead of our plug, so tell the spinner
> to not allow preemption.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>   tests/i915/gem_ctx_engines.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tests/i915/gem_ctx_engines.c b/tests/i915/gem_ctx_engines.c
> index 3ecade417..d47cbdd7c 100644
> --- a/tests/i915/gem_ctx_engines.c
> +++ b/tests/i915/gem_ctx_engines.c
> @@ -283,7 +283,8 @@ static void execute_one(int i915)
>   
>   			spin = igt_spin_new(i915,
>   					    .ctx = param.ctx_id,
> -					    .engine = 0);
> +					    .engine = 0,
> +					    .flags = IGT_SPIN_NO_PREEMPTION);
>   
>   			igt_debug("Testing with map of %d engines\n", i + 1);
>   			memset(&engines.engines, -1, sizeof(engines.engines));
> 

The no-op batch preempts the spinner? How does that affect the busy 
check on the no-op batch?

Regards,

Tvrtko