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Date: Sat, 14 Mar 2015 15:35:58 +0100
From: Oleg Nesterov <oleg@redhat.com>
To: Josh Triplett <josh@joshtriplett.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andy Lutomirski <luto@amacapital.net>, Ingo Molnar <mingo@redhat.com>,
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        "H. Peter Anvin" <hpa@zytor.com>, Rik van Riel <riel@redhat.com>,
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        Michael Kerrisk <mtk.manpages@gmail.com>, linux-kernel@vger.kernel.org,
        linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        x86@kernel.org
Subject: Re: [PATCH 6/6] clone4: Introduce new CLONE_FD flag to get task
	exit notification via fd
Message-ID: <20150314143558.GB12086@redhat.com>
References: <cover.1426180120.git.josh@joshtriplett.org> <9c39c576e1d9a9912b4aec54d833a73a84d2f592.1426180120.git.josh@joshtriplett.org>
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On 03/12, Josh Triplett wrote:
>
> @@ -598,7 +600,9 @@ static void exit_notify(struct task_struct *tsk, int group_dead)
>  	if (group_dead)
>  		kill_orphaned_pgrp(tsk->group_leader, NULL);
>  
> -	if (unlikely(tsk->ptrace)) {
> +	if (tsk->autoreap) {
> +		autoreap = true;
> +	} else if (unlikely(tsk->ptrace)) {
>  		int sig = thread_group_leader(tsk) &&
>  				thread_group_empty(tsk) &&
>  				!ptrace_reparented(tsk) ?
> @@ -612,8 +616,10 @@ static void exit_notify(struct task_struct *tsk, int group_dead)
>  	}
>  
>  	tsk->exit_state = autoreap ? EXIT_DEAD : EXIT_ZOMBIE;
> -	if (tsk->exit_state == EXIT_DEAD)
> +	if (tsk->exit_state == EXIT_DEAD) {
>  		list_add(&tsk->ptrace_entry, &dead);
> +		clonefd_do_notify(tsk);
> +	}

And even ignoring semantics issues, this change looks simply buggy anyway ;)

How can we do list_add(&tsk->ptrace_entry) if it is traced by _another_ task?
->ptrace_entry is used by debugger.

Oleg.