Re: [PATCH 1/1] move exit_task_namespaces() outside of exit_notify()

[Andrew Vagin <avagin@parallels.com>]

On Sat, Apr 13, 2013 at 05:55:21PM +0200, Oleg Nesterov wrote:
> exit_notify() does exit_task_namespaces() after
> forget_original_parent(). This was needed to ensure that ->nsproxy
> can't be cleared prematurely, an exiting child we are going to
> reparent can do do_notify_parent() and use the parent's (ours) pid_ns.
> 
> However, after 32084504 "pidns: use task_active_pid_ns in
> do_notify_parent" ->nsproxy != NULL is no longer needed, we rely
> on task_active_pid_ns().
> 
> Move exit_task_namespaces() from exit_notify() to do_exit(), after
> exit_fs() and before exit_task_work().
> 
> This solves the problem reported by Andrey, free_ipc_ns()->shm_destroy()
> does fput() which needs task_work_add(). And this allows us do simplify
> exit_notify(), we can avoid unlock/lock(tasklist) and we can change
> ->exit_state instead of PF_EXITING in forget_original_parent().
>

It looks good for me. kmemleak doesn't report any leaks. CRIU test
cases, which use namespaces, work without any errors.

Thanks.

Acked-by: Andrey Vagin <avagin@openvz.org>

> Reported-by: Andrey Vagin <avagin@openvz.org>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> 
> --- x/kernel/exit.c
> +++ x/kernel/exit.c
> @@ -649,7 +649,6 @@ static void exit_notify(struct task_stru
>  	 *	jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
>  	 */
>  	forget_original_parent(tsk);
> -	exit_task_namespaces(tsk);
>  
>  	write_lock_irq(&tasklist_lock);
>  	if (group_dead)
> @@ -795,6 +794,7 @@ void do_exit(long code)
>  	exit_shm(tsk);
>  	exit_files(tsk);
>  	exit_fs(tsk);
> +	exit_task_namespaces(tsk);
>  	exit_task_work(tsk);
>  	check_stack_usage();
>  	exit_thread();
>