Message-ID: <557EA388.5090902@redhat.com>
Date: Mon, 15 Jun 2015 12:06:00 +0200
From: Florian Weimer <fweimer@redhat.com>
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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
References: <cover.1426376419.git.josh@joshtriplett.org> <556818A7.3030804@redhat.com> <1775865.3maNSqUW4u@tjmaciei-mobl4>
In-Reply-To: <1775865.3maNSqUW4u@tjmaciei-mobl4>
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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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