[Intel-gfx] [PATCH] drm/i915/gem: Check for a closed context when looking up an engine

[Tvrtko Ursulin]

On 16/03/2020 16:14, Chris Wilson wrote:
> Beware that the context may already be closed as we try to lookup an
> engine.
> 
> Closes: https://gitlab.freedesktop.org/drm/intel/issues/1389
> Fixes: 130a95e9098e ("drm/i915/gem: Consolidate ctx->engines[] release")
> 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/gem/i915_gem_context.h | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.h b/drivers/gpu/drm/i915/gem/i915_gem_context.h
> index 57b7ae2893e1..a09fd67fed1d 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_context.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.h
> @@ -192,12 +192,16 @@ i915_gem_context_unlock_engines(struct i915_gem_context *ctx)
>   static inline struct intel_context *
>   i915_gem_context_get_engine(struct i915_gem_context *ctx, unsigned int idx)
>   {
> -	struct intel_context *ce = ERR_PTR(-EINVAL);
> +	struct intel_context *ce;
>   
>   	rcu_read_lock(); {
>   		struct i915_gem_engines *e = rcu_dereference(ctx->engines);
> -		if (likely(idx < e->num_engines && e->engines[idx]))
> +		if (unlikely(e == NULL)) /* context was closed! */
> +			ce = ERR_PTR(-ENOENT);
> +		else if (likely(idx < e->num_engines && e->engines[idx]))
>   			ce = intel_context_get(e->engines[idx]);
> +		else
> +			ce = ERR_PTR(-EINVAL);
>   	} rcu_read_unlock();
>   
>   	return ce;
> 

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Regards,

Tvrtko