connector: Fix proc_event_num_listeners count not cleared

When we register a cn_proc listening event, the proc_event_num_listener
variable will be incremented by one, but if PROC_CN_MCAST_IGNORE is
not called, the count will not decrease.
This will cause the proc_*_connector function to take the wrong path.
It will reappear when the forkstat tool exits via ctrl + c.
We solve this problem by determining whether
there are still listeners to clear proc_event_num_listener.

Signed-off-by: wangkeqi <wangkeqiwang@didiglobal.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: wangkeqi

drivers/connector/cn_proc.c

@@ -108,8 +108,9 @@ static inline void send_msg(struct cn_msg *msg)
 		filter_data[1] = 0;
 	}
 
-	cn_netlink_send_mult(msg, msg->len, 0, CN_IDX_PROC, GFP_NOWAIT,
-			     cn_filter, (void *)filter_data);
+	if (cn_netlink_send_mult(msg, msg->len, 0, CN_IDX_PROC, GFP_NOWAIT,
+			     cn_filter, (void *)filter_data) == -ESRCH)
+		atomic_set(&proc_event_num_listeners, 0);
 
 	local_unlock(&local_event.lock);
 }