Re: [PATCH] drm/xe: Use missing lock in relay_needs_worker

[Michal Wajdeczko <michal.wajdeczko@intel.com>]

On 03.06.2024 10:17, Nirmoy Das wrote:
> Add missing lock that is protecting relay->incoming_actions.

good catch!

> 
> Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
> Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_guc_relay.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_guc_relay.c b/drivers/gpu/drm/xe/xe_guc_relay.c
> index c3bbaf474f9a..ade6162dc259 100644
> --- a/drivers/gpu/drm/xe/xe_guc_relay.c
> +++ b/drivers/gpu/drm/xe/xe_guc_relay.c
> @@ -761,7 +761,14 @@ static void relay_process_incoming_action(struct xe_guc_relay *relay)
>  
>  static bool relay_needs_worker(struct xe_guc_relay *relay)
>  {
> -	return !list_empty(&relay->incoming_actions);
> +	bool is_empty;
> +
> +	spin_lock(&relay->lock);
> +	is_empty = list_empty(&relay->incoming_actions);
> +	spin_unlock(&relay->lock);
> +
> +	return !is_empty;
> +
>  }

alternate solution could be to just rely on the new return value from
relay_process_incoming_action() that could tell us if there was nothing
to dequeue so then we wont start new worker (at potential cost of one
extra worker cycle to see that), but this LGTM too, so

Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>