linux-kernel - Re: [PATCH] prctl: add PR_{GET,SET}_KILL_DESCENDANTS_ON

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Message-ID: <20181128144230.GG30395@redhat.com>
Date:   Wed, 28 Nov 2018 15:42:31 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     Jürg Billeter <j@...ron.ch>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Eric Biederman <ebiederm@...ssion.com>,
        Kees Cook <keescook@...omium.org>,
        Andy Lutomirski <luto@...nel.org>, linux-api@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] prctl: add PR_{GET,SET}_KILL_DESCENDANTS_ON_EXIT

On 11/27, Jürg Billeter wrote:
>
> @@ -704,6 +713,9 @@ static void exit_notify(struct task_struct *tsk, int group_dead)
>  	struct task_struct *p, *n;
>  	LIST_HEAD(dead);
>  
> +	if (group_dead && tsk->signal->kill_descendants_on_exit)
> +		walk_process_tree(tsk, kill_descendant_visitor, NULL);

Well, this is not exactly right, at least this is suboptimal in that
other sub-threads can too call walk_process_tree(kill_descendant_visitor)
later for no reason.