linux-kernel - Re: [PATCH v2 0/7] CLONE_FD: Task exit notification via file descriptor

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Date:	Mon, 15 Jun 2015 12:06:00 +0200
From:	Florian Weimer <fweimer@...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>,
	Oleg Nesterov <oleg@...hat.com>,
	"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 0/7] CLONE_FD: Task exit notification via file descriptor

On 05/29/2015 10:27 PM, Thiago Macieira wrote:

>> It has been suggested (e.g.,
>> <https://sourceware.org/bugzilla/show_bug.cgi?id=15661#c3>) that you can
>> use the existing clone(2) without specifying SIGCHLD to create a new
>> process.  The resulting child process is not supposed to show up in
>> wait(2), only in a waitpid(2) (or similar) explicitly specifying the
>> PID.  Is this not the case?
> 
> Hi Florian
> 
> That sounds orthogonal to what we're looking for. Our objective is to get 
> notification of when the child exited without resorting to SIGCHLD. If we use 
> the regular clone(2) without SIGCHLD and without CLONE_FD, we get no 
> notification. The only way to know of the child's termination is by a blocking 
> waitpid(2), like you indicated, which is counter productive to our needs.
> 
> We need something we can select(2)/poll(2) on.

Thanks for the clarification.  I agree that this is a separate and quite
sensible use case.

-- 
Florian Weimer / Red Hat Product Security
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