[Intel-gfx] [PATCH 2/3] drm/i915: Do not short-circuit tasklets during reset

[Michel Thierry]

On 7/13/2018 1:35 PM, Chris Wilson wrote:
> Inside intel_engine_is_idle(), we flush the tasklet to ensure that is
> being run in a timely fashion (ksoftirqd has taught us to expect the
> worst). However, if we are in the middle of reset, the HW may not yet be
> ready to execute the submission tasklet and so we must respect the
> disable flag.
> 
> Fixes: dd0cf235d81f ("drm/i915: Speed up idle detection by kicking the tasklets")
> Testcase: igt/drv_selftest/live_hangcheck
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> ---
>   drivers/gpu/drm/i915/intel_engine_cs.c | 11 ++++++-----
>   1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
> index 220050107c48..fccb95ea1315 100644
> --- a/drivers/gpu/drm/i915/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/intel_engine_cs.c
> @@ -989,16 +989,17 @@ bool intel_engine_is_idle(struct intel_engine_cs *engine)
>   
>   	/* Waiting to drain ELSP? */
>   	if (READ_ONCE(engine->execlists.active)) {
> -		struct intel_engine_execlists *execlists = &engine->execlists;
> +		struct tasklet_struct *t = &engine->execlists.tasklet;
>   
>   		local_bh_disable();
> -		if (tasklet_trylock(&execlists->tasklet)) {
> -			execlists->tasklet.func(execlists->tasklet.data);
> -			tasklet_unlock(&execlists->tasklet);
> +		if (tasklet_trylock(t)) {
> +			if (__tasklet_is_enabled(t))

I would add a comment that this catches any reset in progress as it 
isn't as clear as using reset_in_progress (although you explain why in 
the commit message).

Up-to you.

Reviewed-by: Michel Thierry <michel.thierry at intel.com>

> +				t->func(t->data);
> +			tasklet_unlock(t);
>   		}
>   		local_bh_enable();
>   
> -		if (READ_ONCE(execlists->active))
> +		if (READ_ONCE(engine->execlists.active))
>   			return false;
>   	}
>   
>