Re: [Intel-gfx] [PATCH v9 27/70] drm/i915: Make __engine_unpark() compatible with ww locking.

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Mar 23, 2021 at 04:50:16PM +0100, Maarten Lankhorst wrote:
> Take the ww lock around engine_unpark. Because of the
> many many places where rpm is used, I chose the safest option
> and used a trylock to opportunistically take this lock for
> __engine_unpark.

Correct choice, runtime pm resume is on the critical path for dma-fence
(we might need to wake up the device for e.g. atomic modeset commits), so
definitely can't have a dma_resv_lock in here.
-Daniel

> 
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/gt/intel_engine_pm.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pm.c b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
> index 27d9d17b35cb..bddc5c98fb04 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_pm.c
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
> @@ -27,12 +27,16 @@ static void dbg_poison_ce(struct intel_context *ce)
>  		int type = i915_coherent_map_type(ce->engine->i915);
>  		void *map;
>  
> +		if (!i915_gem_object_trylock(obj))
> +			return;
> +
>  		map = i915_gem_object_pin_map(obj, type);
>  		if (!IS_ERR(map)) {
>  			memset(map, CONTEXT_REDZONE, obj->base.size);
>  			i915_gem_object_flush_map(obj);
>  			i915_gem_object_unpin_map(obj);
>  		}
> +		i915_gem_object_unlock(obj);
>  	}
>  }
>  
> -- 
> 2.31.0
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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