linux-kernel - Re: [PATCH v2 5/7] clone4: Add a CLONE_AUTOREAP flag to automatically reap the child process

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Message-ID: <20150320190914.GA28357@redhat.com>
Date:	Fri, 20 Mar 2015 20:09:14 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Thiago Macieira <thiago.macieira@...el.com>
Cc:	Josh Triplett <josh@...htriplett.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Kees Cook <keescook@...omium.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	"H. Peter Anvin" <hpa@...or.com>, Rik van Riel <riel@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v2 5/7] clone4: Add a CLONE_AUTOREAP flag to
	automatically reap the child process

On 03/20, Thiago Macieira wrote:
>
> On Friday 20 March 2015 19:14:04 Oleg Nesterov wrote:
> > Also. I forgot that the kernel always resets ->exit_signal to SIGCHLD on
> > exec or reparenting. Reparenting is probably fine. But what about exec?
> > Should it keep ->exit_signal == 0 if "autoreap" ? I think it should not, to
> > avoid the strange special case.
>
> Not delivering any signal was the objective of this patch series, so yes
> exit_signal == 0 should survive an exec and even re-exec.

OK, but then perhaps we should never send SIGCHLD (on exit) if "autoreap",
to make the logic simple.

And copy_process() should probably do

	if ((clone_flags & CSIGNAL) && (clone_flags && CLONE_AUTOREAP))
		return -EINVAL;

so that we still can change this behaviour later.

Oleg.

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