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Date:   Fri, 17 May 2019 00:53:41 +1000
From:   Aleksa Sarai <cyphar@cyphar.com>
To:     Christian Brauner <christian@brauner.io>
Cc:     Daniel Colascione <dancol@google.com>,
        Jann Horn <jannh@google.com>, Oleg Nesterov <oleg@redhat.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        David Howells <dhowells@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        elena.reshetova@intel.com, Kees Cook <keescook@chromium.org>,
        Andy Lutomirski <luto@amacapital.net>,
        Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <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, linux-parisc@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org,
        linux-sh@vger.kernel.org, sparclinux@vger.kernel.org,
        linux-xtensa@linux-xtensa.org,
        Linux API <linux-api@vger.kernel.org>,
        linux-arch@vger.kernel.org,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@vger.kernel.org>
Subject: Re: [PATCH 1/2] pid: add pidfd_open()
Message-ID: <20190516145341.xx7bpyakezvpqujj@yavin>
References: <20190515100400.3450-1-christian@brauner.io>
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 <20190516130813.i66ujfzftbgpqhnh@brauner.io>
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On 2019-05-16, Christian Brauner <christian@brauner.io> wrote:
> On Wed, May 15, 2019 at 10:45:06AM -0700, Daniel Colascione wrote:
> > On Wed, May 15, 2019 at 3:04 AM Christian Brauner <christian@brauner.io=
> wrote:
> > > +       if (pid <=3D 0)
> > > +               return -EINVAL;
> >=20
> > WDYT of defining pid =3D=3D 0 to mean "open myself"?
>=20
> I'm torn. It be a nice shortcut of course but pid being 0 is usually an
> indicator for child processes. So unless the getpid() before
> pidfd_open() is an issue I'd say let's leave it as is. If you really
> want the shortcut might -1 be better?

I'd suggest not using negative numbers, and instead reserving them for
PIDTYPE_TGID if we ever want to have that in the future. IMHO, doing

  pfd =3D pidfd_open(getpid(), 0);

is not the end of the world.


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

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