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Date:   Fri, 17 May 2019 01:12:02 +1000
From:   Aleksa Sarai <cyphar@cyphar.com>
To:     Oleg Nesterov <oleg@redhat.com>
Cc:     Christian Brauner <christian@brauner.io>, jannh@google.com,
        viro@zeniv.linux.org.uk, torvalds@linux-foundation.org,
        linux-kernel@vger.kernel.org, arnd@arndb.de,
        akpm@linux-foundation.org, dhowells@redhat.com,
        ebiederm@xmission.com, elena.reshetova@intel.com,
        keescook@chromium.org, luto@amacapital.net, luto@kernel.org,
        tglx@linutronix.de, linux-alpha@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org,
        linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org,
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        linux-s390@vger.kernel.org, linux-sh@vger.kernel.org,
        sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org,
        linux-api@vger.kernel.org, linux-arch@vger.kernel.org,
        linux-kselftest@vger.kernel.org, joel@joelfernandes.org,
        dancol@google.com, serge@hallyn.com,
        Geert Uytterhoeven <geert@linux-m68k.org>
Subject: Re: [PATCH v1 1/2] pid: add pidfd_open()
Message-ID: <20190516151202.hrawrx7hxllmz2di@yavin>
References: <20190516135944.7205-1-christian@brauner.io>
 <20190516142659.GB22564@redhat.com>
 <20190516145607.j43xyj26k6l5vmbd@yavin>
 <20190516150611.GC22564@redhat.com>
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On 2019-05-16, Oleg Nesterov <oleg@redhat.com> wrote:
> On 05/17, Aleksa Sarai wrote:
> > On 2019-05-16, Oleg Nesterov <oleg@redhat.com> wrote:
> > > On 05/16, Christian Brauner wrote:
> > > > With the introduction of pidfds through CLONE_PIDFD it is possible =
to
> > > > created pidfds at process creation time.
> > >
> > > Now I am wondering why do we need CLONE_PIDFD, you can just do
> > >
> > > 	pid =3D fork();
> > > 	pidfd_open(pid);
> >
> > While the race window would be exceptionally short, there is the
> > possibility that the child will die
>=20
> Yes,
>=20
> > and their pid will be recycled
> > before you do pidfd_open().
>=20
> No.
>=20
> Unless the caller's sub-thread does wait() before pidfd_open(), of course.
> Or unless you do signal(SIGCHILD, SIG_IGN).

What about CLONE_PARENT?

--=20
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>

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