Re: [PATCH V3] exit: trigger panic when global init has exited

[Oleg Nesterov <oleg@redhat.com>]

On 03/19, qianli zhao wrote:
>
> I will think about the risks of movement of the decrement of
> signal->live before exit_signal().
> If is difficult to judge movement of the decrement of signal->live is
> safe,how about only test 'signal->live==1' not use group_dead?
>
> Such as:
> diff --git a/kernel/exit.c b/kernel/exit.c
> index 04029e3..87f3595 100644
> --- a/kernel/exit.c
> +++ b/kernel/exit.c
> @@ -767,6 +767,17 @@ void __noreturn do_exit(long code)
>         validate_creds_for_do_exit(tsk);
>
>         /*
> +        * If global init has exited,
> +        * panic immediately to get a useable coredump.
> +        */
> +       if (unlikely(is_global_init(tsk) &&
> +           ((atomic_read(&tsk->signal->live) == 1) ||    /*current is
> last init thread*/

Just suppose signal->live == 2 and both init's sub-threads exit at the
same time. They both can see signal->live == 2, panic() won't be called.

Oleg.