[dm-devel] [PATCH 34/35] multipathd: uxlsnr: drop client_lock

[Benjamin Marzinski]

On Fri, Sep 10, 2021 at 01:41:19PM +0200, mwilck at suse.com wrote:
> From: Martin Wilck <mwilck at suse.com>
> 
> The list of clients is never changed anywhere except in
> uxsock_listen(). No need to lock.
> 
> Signed-off-by: Martin Wilck <mwilck at suse.com>
> ---
>  multipathd/uxlsnr.c | 21 ++-------------------
>  1 file changed, 2 insertions(+), 19 deletions(-)
> 
> diff --git a/multipathd/uxlsnr.c b/multipathd/uxlsnr.c
> index c18b2c4..7b763b6 100644
> --- a/multipathd/uxlsnr.c
> +++ b/multipathd/uxlsnr.c
> @@ -89,7 +89,6 @@ enum {
>  static __attribute__((unused)) char ___a[-(MIN_POLLS <= 0)];
>  
>  static LIST_HEAD(clients);
> -static pthread_mutex_t client_lock = PTHREAD_MUTEX_INITIALIZER;
>  static struct pollfd *polls;
>  static int notify_fd = -1;
>  static int idle_fd = -1;
> @@ -150,15 +149,13 @@ static void new_client(int ux_sock)
>  	c->is_root = _socket_client_is_root(c->fd);
>  
>  	/* put it in our linked list */
> -	pthread_mutex_lock(&client_lock);
>  	list_add_tail(&c->node, &clients);
> -	pthread_mutex_unlock(&client_lock);
>  }
>  
>  /*
>   * kill off a dead client
>   */
> -static void _dead_client(struct client *c)
> +static void dead_client(struct client *c)

There are also leading underscores and comments about the clients lock
for __get_soonest_timeout() and __need_lock(). We should probably remove
those as well.

-Ben

>  {
>  	int fd = c->fd;
>  	list_del_init(&c->node);
> @@ -170,14 +167,6 @@ static void _dead_client(struct client *c)
>  	close(fd);
>  }
>  
> -static void dead_client(struct client *c)
> -{
> -	pthread_cleanup_push(cleanup_mutex, &client_lock);
> -	pthread_mutex_lock(&client_lock);
> -	_dead_client(c);
> -	pthread_cleanup_pop(1);
> -}
> -
>  static void free_polls (void)
>  {
>  	if (polls)
> @@ -194,11 +183,9 @@ void uxsock_cleanup(void *arg)
>  	close(notify_fd);
>  	free(watch_config_dir);
>  
> -	pthread_mutex_lock(&client_lock);
>  	list_for_each_entry_safe(client_loop, client_tmp, &clients, node) {
> -		_dead_client(client_loop);
> +		dead_client(client_loop);
>  	}
> -	pthread_mutex_unlock(&client_lock);
>  
>  	cli_exit();
>  	free_polls();
> @@ -668,8 +655,6 @@ void *uxsock_listen(long ux_sock, void *trigger_data)
>  		struct timespec __timeout, *timeout;
>  
>  		/* setup for a poll */
> -		pthread_mutex_lock(&client_lock);
> -		pthread_cleanup_push(cleanup_mutex, &client_lock);
>  		num_clients = 0;
>  		list_for_each_entry(c, &clients, node) {
>  			num_clients++;
> @@ -738,8 +723,6 @@ void *uxsock_listen(long ux_sock, void *trigger_data)
>                  n_pfds = i;
>  		timeout = __get_soonest_timeout(&__timeout);
>  
> -		pthread_cleanup_pop(1);
> -
>  		/* most of our life is spent in this call */
>  		poll_count = ppoll(polls, n_pfds, timeout, &mask);
>  
> -- 
> 2.33.0