linux-kernel - Re: For review: pidfd

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Date:   Mon, 23 Sep 2019 22:41:19 +0200
From:   Florian Weimer <fw@...eb.enyo.de>
To:     "Michael Kerrisk \(man-pages\)" <mtk.manpages@...il.com>
Cc:     Christian Brauner <christian@...uner.io>,
        Jann Horn <jannh@...gle.com>,
        Daniel Colascione <dancol@...gle.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Linux API <linux-api@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        linux-man <linux-man@...r.kernel.org>,
        Oleg Nesterov <oleg@...hat.com>
Subject: Re: For review: pidfd_open(2) manual page

* Michael Kerrisk:

>>>        static
>>>        int pidfd_open(pid_t pid, unsigned int flags)
>>>        {
>>>            return syscall(__NR_pidfd_open, pid, flags);
>>>        }
>> 
>> Please call this function something else (not pidfd_open), so that the
>> example continues to work if glibc provides the system call wrapper.
>
> I figured that if the syscall does get added to glibc, then I would
> modify the example. In the meantime, this does seem the most natural
> way of doing things, since the example then uses the real syscall
> name as it would be used if there were a wrapper function.

The problem is that programs do this as well, so they fail to build
once they are built on a newer glibc version.

> But, this leads to the question: what do you think the likelihood
> is that this system call will land in glibc?

Quite likely.  It's easy enough to document, there are no P&C issues,
and it doesn't need any new types.

pidfd_send_signal is slightly more difficult because we probably need
to add rt_sigqueueinfo first, for consistency.