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

From: Andrew Vagin
Date: Thu Jun 13 2013 - 05:27:00 EST


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@xxxxxxxxxx>

> Reported-by: Andrey Vagin <avagin@xxxxxxxxxx>
> Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
>
> --- 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();
>
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