Re: [PATCH 3/5] drm/i915: Kill the tasklet then disable

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

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

> Disabling the tasklet leaves it if scheduled on the ready to run list
> until it is re-enabled. This will leave the ksoftird thread spinning
> until satisfied. To prevent this situation on starting the GPU reset, we
> want to kill the tasklet first and then disable. The same problem will
> arise when a tasklet is scheduled from another device, so a better
> solution is required for the general case.
>
> Reported-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Fixes: 1f7b847d72c3 ("drm/i915: Disable engine->irq_tasklet around resets")
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

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

> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_gem.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 48922ff454e6..3c2c2296c1dc 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -2651,8 +2651,8 @@ int i915_gem_reset_prepare(struct drm_i915_private *dev_priv)
>  		 * Turning off the engine->irq_tasklet until the reset is over
>  		 * prevents the race.
>  		 */
> -		tasklet_disable(&engine->irq_tasklet);
>  		tasklet_kill(&engine->irq_tasklet);
> +		tasklet_disable(&engine->irq_tasklet);
>  
>  		if (engine->irq_seqno_barrier)
>  			engine->irq_seqno_barrier(engine);
> -- 
> 2.11.0
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