linux-kernel - Re: For review: pidfd

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Date:   Mon, 23 Sep 2019 22:57:40 +0200
From:   "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:     Florian Weimer <fw@...eb.enyo.de>
Cc:     mtk.manpages@...il.com, 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

Hello Florian,

On 9/23/19 10:41 PM, Florian Weimer wrote:
> * 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 isn't such a failure a good thing? I mean: it encourages
people to rid their programs of uses of syscall(2).

>> 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.

Okay.

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

Okay. I see that's a little more problematic.

Cheers,

Michael

-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/