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

From: Florian Weimer <fweimer@redhat.com>
To: Thiago Macieira <thiago.macieira@intel.com>
Cc: Josh Triplett <josh@joshtriplett.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Andrew Morton <akpm@linux-foundation.org>,
	Andy Lutomirski <luto@kernel.org>, Ingo Molnar <mingo@redhat.com>,
	Kees Cook <keescook@chromium.org>,
	Oleg Nesterov <oleg@redhat.com>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	"H. Peter Anvin" <hpa@zytor.com>, Rik van Riel <riel@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	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 v2 0/7] CLONE_FD: Task exit notification via file descriptor
Date: Mon, 15 Jun 2015 12:06:00 +0200	[thread overview]
Message-ID: <557EA388.5090902@redhat.com> (raw)
In-Reply-To: <1775865.3maNSqUW4u@tjmaciei-mobl4>

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