[CRIU] [PATCH RFC 23/30] inet: Use task_st futex for notification instead of per-port

[Pavel Emelyanov]

Why doesn't per-socket notification work?

On 11/01/2016 05:34 PM, Kirill Tkhai wrote:
> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
> ---
>  criu/sk-inet.c |   26 ++++++++++++++++++++------
>  1 file changed, 20 insertions(+), 6 deletions(-)
> 
> diff --git a/criu/sk-inet.c b/criu/sk-inet.c
> index 6a0a2d2..8832c91 100644
> --- a/criu/sk-inet.c
> +++ b/criu/sk-inet.c
> @@ -33,7 +33,7 @@ struct inet_port {
>  	int port;
>  	int type;
>  	struct list_head type_list;
> -	futex_t users;
> +	atomic_t users;
>  	mutex_t reuseaddr_lock;
>  	struct list_head list;
>  };
> @@ -45,7 +45,7 @@ static struct inet_port *port_add(struct inet_sk_info *ii, int port)
>  
>  	list_for_each_entry(e, &inet_ports, list)
>  		if (e->type == type && e->port == port) {
> -			futex_inc(&e->users);
> +			atomic_inc(&e->users);
>  			goto out_link;
>  		}
>  
> @@ -57,8 +57,7 @@ static struct inet_port *port_add(struct inet_sk_info *ii, int port)
>  
>  	e->port = port;
>  	e->type = type;
> -	futex_init(&e->users);
> -	futex_inc(&e->users);
> +	atomic_set(&e->users, 1);
>  	mutex_init(&e->reuseaddr_lock);
>  	INIT_LIST_HEAD(&e->type_list);
>  
> @@ -514,6 +513,19 @@ static int inet_validate_address(InetSkEntry *ie)
>  	return -1;
>  }
>  
> +static void dec_users_and_wake(struct inet_port *port)
> +{
> +	struct fdinfo_list_entry *fle;
> +	struct inet_sk_info *ii;
> +
> +	if (atomic_dec_return(&port->users))
> +		return;
> +	list_for_each_entry(ii, &port->type_list, port_list) {
> +		fle = file_master(&ii->d);
> +		set_fds_event(fle->pid);
> +	}
> +}
> +
>  static int post_open_inet_sk(struct file_desc *d, int sk)
>  {
>  	struct inet_sk_info *ii;
> @@ -536,7 +548,8 @@ static int post_open_inet_sk(struct file_desc *d, int sk)
>  	if (ii->ie->opts->reuseaddr)
>  		return 0;
>  
> -	futex_wait_until(&ii->port->users, 0);
> +	while (atomic_read(&ii->port->users))
> +		wait_fds_event();
>  
>  	val = ii->ie->opts->reuseaddr;
>  	if (restore_opt(sk, SOL_SOCKET, SO_REUSEADDR, &val))
> @@ -554,6 +567,7 @@ int restore_ip_opts(int sk, IpOptsEntry *ioe)
>  
>  	return ret;
>  }
> +
>  static int open_inet_sk(struct file_desc *d)
>  {
>  	struct inet_sk_info *ii;
> @@ -641,7 +655,7 @@ static int open_inet_sk(struct file_desc *d)
>  			inet_connect(sk, ii))
>  		goto err;
>  done:
> -	futex_dec_and_wake(&ii->port->users);
> +	dec_users_and_wake(ii->port);
>  
>  	if (rst_file_params(sk, ie->fown, ie->flags))
>  		goto err;
> 
> .
>