Re: [PATCH v4 2/2] wifi: ath11k: move update channel list to worker when wait flag is set

[Kalle Valo <kvalo@kernel.org>]

Kang Yang <quic_kangyang@quicinc.com> writes:

> From: Wen Gong <quic_wgong@quicinc.com>
>
> With previous patch "wifi: ath11k: move update channel list from update
> reg worker to reg notifier", ath11k_reg_update_chan_list() will be
> called during reg_process_self_managed_hint().
>
> reg_process_self_managed_hint() will hold rtnl_lock all the time.
> But ath11k_reg_update_chan_list() may increase the occupation time of
> rtnl_lock, because wait flag is set and wait_for_completion_timeout()
> will be called when 11d/hw scan is running.
>
> Should minimize the occupation time of rtnl_lock as much as possible.
>
> Move update channel list operation to a new worker, so that
> wait_for_completion_timeout() won't be called and will not increase the
> occupation time of rtnl_lock.

Maybe the last two paragraphs could be merged (and edited) like this:

We should minimize the occupation time of rtnl_lock as much as possible
to avoid interfering with rest of the system. So move the update channel
list operation to a new worker, so that wait_for_completion_timeout()
won't be called and will not increase the occupation time of rtnl_lock.

> --- a/drivers/net/wireless/ath/ath11k/core.h
> +++ b/drivers/net/wireless/ath/ath11k/core.h
> @@ -685,7 +685,7 @@ struct ath11k {
>  	struct mutex conf_mutex;
>  	/* protects the radio specific data like debug stats, ppdu_stats_info stats,
>  	 * vdev_stop_status info, scan data, ath11k_sta info, ath11k_vif info,
> -	 * channel context data, survey info, test mode data.
> +	 * channel context data, survey info, test mode data, channel_update_queue.
>  	 */
>  	spinlock_t data_lock;

Usually is best to add a comment the data you are protecting, in this
case the new fields in struct ath11k.

> @@ -743,6 +743,8 @@ struct ath11k {
>  	struct completion bss_survey_done;
>  
>  	struct work_struct regd_update_work;
> +	struct work_struct channel_update_work;
> +	struct list_head channel_update_queue;

So here add '/* protected with data_lock */' or similar before channel_update_queue.

> @@ -231,8 +206,16 @@ int ath11k_reg_update_chan_list(struct ath11k *ar, bool wait)
>  		}
>  	}
>  
> -	ret = ath11k_wmi_send_scan_chan_list_cmd(ar, params);
> -	kfree(params);
> +	if (wait) {
> +		spin_lock_bh(&ar->data_lock);
> +		list_add_tail(&params->list, &ar->channel_update_queue);
> +		spin_unlock_bh(&ar->data_lock);
> +
> +		queue_work(ar->ab->workqueue, &ar->channel_update_work);
> +	} else {
> +		ret = ath11k_wmi_send_scan_chan_list_cmd(ar, params);
> +		kfree(params);
> +	}

You can avoid the else branch like this:

if (wait) {
	spin_lock_bh(&ar->data_lock);
	list_add_tail(&params->list, &ar->channel_update_queue);
	spin_unlock_bh(&ar->data_lock);

	queue_work(ar->ab->workqueue, &ar->channel_update_work);

        return 0;
}

ret = ath11k_wmi_send_scan_chan_list_cmd(ar, params);
kfree(params);

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