[CRIU] [PATCH v4 05/41] cr-restore: Open transport socket earlier

[Andrei Vagin]

On Thu, May 04, 2017 at 07:05:40PM +0300, Kirill Tkhai wrote:
> I need named socket to communicate with pid_ns helpers
> (see next patches) and receive answer from them
> (it's impossible to send answer to unnamed socket).
> As we already have transport socket, we'll reuse it
> for the above goal too.
> 
> This patch makes transport sockets be created before
> creation of children tasks. Also, now it's created
> not only for alive tasks.
> 
> (It seems, it won't be good to make futex_lock and
> futex_mutex union unless we define one as equal type
> to other using typedef, but anyway I'd happy to hear
> your opinions).
> 
> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
> ---
>  criu/cr-restore.c       |    6 +++---
>  criu/files.c            |   20 ++++++++++++--------
>  criu/include/rst_info.h |    1 +
>  criu/pstree.c           |    2 +-
>  4 files changed, 17 insertions(+), 12 deletions(-)
> 
> diff --git a/criu/cr-restore.c b/criu/cr-restore.c
> index 1a99797dc..9c6d4b041 100644
> --- a/criu/cr-restore.c
> +++ b/criu/cr-restore.c
> @@ -1585,6 +1585,9 @@ static int restore_task_with_children(void *_arg)
>  		BUG();
>  	}
>  
> +	if (open_transport_socket())
> +		goto err;
> +
>  	timing_start(TIME_FORK);
>  
>  	if (create_children_and_session())
> @@ -1597,9 +1600,6 @@ static int restore_task_with_children(void *_arg)
>  
>  	restore_pgid();
>  
> -	if (open_transport_socket())
> -		return -1;
> -
>  	if (current->parent == NULL) {
>  		/*
>  		 * Wait when all tasks passed the CR_STATE_FORKING stage.
> diff --git a/criu/files.c b/criu/files.c
> index 01cd4c0e9..eba506608 100644
> --- a/criu/files.c
> +++ b/criu/files.c
> @@ -1325,6 +1325,7 @@ int shared_fdt_prepare(struct pstree_item *item)
>  
>  		rsti(parent)->fdt = fdt;
>  
> +		mutex_init(&fdt->fdt_mutex);
>  		futex_init(&fdt->fdt_lock);
>  		fdt->nr = 1;
>  		fdt->pid = vpid(parent);
> @@ -1635,29 +1636,32 @@ int open_transport_socket(void)
>  	struct fdt *fdt = rsti(current)->fdt;
>  	pid_t pid = vpid(current);
>  	struct sockaddr_un saddr;
> -	int sock, slen;
> +	int sock, slen, ret = -1;
>  
> -	if (!task_alive(current) || (fdt && fdt->pid != pid))
> -		return 0;
> +	if (fdt)
> +		mutex_lock(&fdt->fdt_mutex);
>  
>  	sock = socket(PF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC, 0);
>  	if (sock < 0) {
>  		pr_perror("Can't create socket");
> -		return -1;
> +		goto out;
>  	}
>  
>  	transport_name_gen(&saddr, &slen, pid);
>  	if (bind(sock, (struct sockaddr *)&saddr, slen) < 0) {
>  		pr_perror("Can't bind transport socket %s", saddr.sun_path + 1);
>  		close(sock);
> -		return -1;
> +		goto out;
>  	}
>  
>  	if (install_service_fd(TRANSPORT_FD_OFF, sock) < 0) {
>  		close(sock);
> -		return -1;
> +		goto out;
>  	}
>  	close(sock);
> -
> -	return 0;
> +	ret = 0;
> +out:
> +	if (fdt)
> +		mutex_unlock(&fdt->fdt_mutex);
> +	return ret;
>  }
> diff --git a/criu/include/rst_info.h b/criu/include/rst_info.h
> index 92dfc9d93..1860c21fc 100644
> --- a/criu/include/rst_info.h
> +++ b/criu/include/rst_info.h
> @@ -21,6 +21,7 @@ struct fdt {
>  	 * The fdt table was restrored, if fdt_lock is equal to nr + 1
>  	 */
>  	futex_t			fdt_lock;
> +	mutex_t			fdt_mutex;

can you write a comment why we need this mutex
>  };
>  
>  struct _MmEntry;
> diff --git a/criu/pstree.c b/criu/pstree.c
> index b73f4405a..315f533ba 100644
> --- a/criu/pstree.c
> +++ b/criu/pstree.c
> @@ -258,7 +258,7 @@ struct pstree_item *__alloc_pstree_item(bool rst, int level)
>  void init_pstree_helper(struct pstree_item *ret)
>  {
>  	ret->pid->state = TASK_HELPER;
> -	rsti(ret)->clone_flags = CLONE_FILES | CLONE_FS;
> +	rsti(ret)->clone_flags = 0;

Why do we need this ^^^
>  	task_entries->nr_helpers++;
>  }
>  
>