Re: [PATCH v5 2/5] drm/i915: Create the locked version of the request create

[Andrzej Hajda <andrzej.hajda@xxxxxxxxx>]

On 12.04.2023 13:33, Andi Shyti wrote:
> Make version of the request creation that doesn't hold any
> lock.
>
> Signed-off-by: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Reviewed-by: Nirmoy Das <nirmoy.das@xxxxxxxxx>
> ---
>   drivers/gpu/drm/i915/i915_request.c | 38 +++++++++++++++++++++--------
>   drivers/gpu/drm/i915/i915_request.h |  2 ++
>   2 files changed, 30 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
> index 630a732aaecca..58662360ac34e 100644
> --- a/drivers/gpu/drm/i915/i915_request.c
> +++ b/drivers/gpu/drm/i915/i915_request.c
> @@ -1028,15 +1028,11 @@ __i915_request_create(struct intel_context *ce, gfp_t gfp)
>   	return ERR_PTR(ret);
>   }
>   
> -struct i915_request *
> -i915_request_create(struct intel_context *ce)
> +static struct i915_request *
> +__i915_request_create_locked(struct intel_context *ce)
>   {
> +	struct intel_timeline *tl = ce->timeline;
>   	struct i915_request *rq;
> -	struct intel_timeline *tl;
> -
> -	tl = intel_context_timeline_lock(ce);
> -	if (IS_ERR(tl))
> -		return ERR_CAST(tl);
>   
>   	/* Move our oldest request to the slab-cache (if not in use!) */
>   	rq = list_first_entry(&tl->requests, typeof(*rq), link);
> @@ -1046,16 +1042,38 @@ i915_request_create(struct intel_context *ce)
>   	intel_context_enter(ce);
>   	rq = __i915_request_create(ce, GFP_KERNEL);
>   	intel_context_exit(ce); /* active reference transferred to request */
> +
>   	if (IS_ERR(rq))
> -		goto err_unlock;
> +		return rq;
>   
>   	/* Check that we do not interrupt ourselves with a new request */
>   	rq->cookie = lockdep_pin_lock(&tl->mutex);
>   
>   	return rq;
> +}
> +
> +struct i915_request *
> +i915_request_create_locked(struct intel_context *ce)
> +{
> +	intel_context_assert_timeline_is_locked(ce->timeline);
> +
> +	return __i915_request_create_locked(ce);
> +}

I wonder if we really need to have such granularity? Leaving only 
i915_request_create_locked and removing __i915_request_create_locked 
would simplify little bit the code,
I guess the cost of calling intel_context_assert_timeline_is_locked 
twice sometimes is not big, or maybe it can be re-arranged, up to you.

Reviewed-by: Andrzej Hajda <andrzej.hajda@xxxxxxxxx>

Regards
Andrzej


> +
> +struct i915_request *
> +i915_request_create(struct intel_context *ce)
> +{
> +	struct i915_request *rq;
> +	struct intel_timeline *tl;
> +
> +	tl = intel_context_timeline_lock(ce);
> +	if (IS_ERR(tl))
> +		return ERR_CAST(tl);
> +
> +	rq = __i915_request_create_locked(ce);
> +	if (IS_ERR(rq))
> +		intel_context_timeline_unlock(tl);
>   
> -err_unlock:
> -	intel_context_timeline_unlock(tl);
>   	return rq;
>   }
>   
> diff --git a/drivers/gpu/drm/i915/i915_request.h b/drivers/gpu/drm/i915/i915_request.h
> index f5e1bb5e857aa..bb48bd4605c03 100644
> --- a/drivers/gpu/drm/i915/i915_request.h
> +++ b/drivers/gpu/drm/i915/i915_request.h
> @@ -374,6 +374,8 @@ struct i915_request * __must_check
>   __i915_request_create(struct intel_context *ce, gfp_t gfp);
>   struct i915_request * __must_check
>   i915_request_create(struct intel_context *ce);
> +struct i915_request * __must_check
> +i915_request_create_locked(struct intel_context *ce);
>   
>   void __i915_request_skip(struct i915_request *rq);
>   bool i915_request_set_error_once(struct i915_request *rq, int error);