Re: [PATCH] connector: Change the judgment conditions for clearing proc_event_num_listeners

[Yin, Fengwei]

On 1/15/2024 3:51 PM, wangkeqi wrote:
> From: wangkeqi <wangkeqiwang@xxxxxxxxxxxxxx>
>
> It is inaccurate to judge whether proc_event_num_listeners is
> cleared by cn_netlink_send_mult returning -ESRCH.
> In the case of stress-ng netlink-proc, -ESRCH will always be returned,
> because netlink_broadcast_filtered will return -ESRCH,
> which may cause stress-ng netlink-proc performance degradation.
> Therefore, the judgment condition is modified to whether
> there is a listener.
>
> Signed-off-by: wangkeqi <wangkeqiwang@xxxxxxxxxxxxxx>

Regarding the original report:

If you fix the issue in a separate patch/commit (i.e. not just a new 
version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
| Closes: 
https://lore.kernel.org/oe-lkp/202401112259.b23a1567-oliver.sang@xxxxxxxxx


Could you please add the tag? Thanks.

> ---
>   drivers/connector/cn_proc.c   | 6 ++++--
>   drivers/connector/connector.c | 6 ++++++
>   include/linux/connector.h     | 1 +
>   3 files changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c
> index 3d5e6d705..b09f74ed3 100644
> --- a/drivers/connector/cn_proc.c
> +++ b/drivers/connector/cn_proc.c
> @@ -108,8 +108,10 @@ static inline void send_msg(struct cn_msg *msg)
>   		filter_data[1] = 0;
>   	}
>   
> -	if (cn_netlink_send_mult(msg, msg->len, 0, CN_IDX_PROC, GFP_NOWAIT,
> -			     cn_filter, (void *)filter_data) == -ESRCH)
> +	if (netlink_has_listeners(get_cdev_nls(), CN_IDX_PROC))
> +		cn_netlink_send_mult(msg, msg->len, 0, CN_IDX_PROC, GFP_NOWAIT,
> +			     cn_filter, (void *)filter_data);
> +	else
>   		atomic_set(&proc_event_num_listeners, 0);
>   
>   	local_unlock(&local_event.lock);
> diff --git a/drivers/connector/connector.c b/drivers/connector/connector.c
> index 7f7b94f61..1b2cd410e 100644
> --- a/drivers/connector/connector.c
> +++ b/drivers/connector/connector.c
> @@ -129,6 +129,12 @@ int cn_netlink_send(struct cn_msg *msg, u32 portid, u32 __group,
>   }
>   EXPORT_SYMBOL_GPL(cn_netlink_send);
>   
> +struct sock *get_cdev_nls(void)
> +{
> +	return cdev.nls;
> +}
> +EXPORT_SYMBOL_GPL(get_cdev_nls);
> +
>   /*
>    * Callback helper - queues work and setup destructor for given data.
>    */
> diff --git a/include/linux/connector.h b/include/linux/connector.h
> index cec2d99ae..255466aea 100644
> --- a/include/linux/connector.h
> +++ b/include/linux/connector.h
> @@ -127,6 +127,7 @@ int cn_netlink_send_mult(struct cn_msg *msg, u16 len, u32 portid,
>    */
>   int cn_netlink_send(struct cn_msg *msg, u32 portid, u32 group, gfp_t gfp_mask);
>   
> +struct sock *get_cdev_nls(void);
>   int cn_queue_add_callback(struct cn_queue_dev *dev, const char *name,
>   			  const struct cb_id *id,
>   			  void (*callback)(struct cn_msg *, struct netlink_skb_parms *));