From: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
To: Florian Weimer <fw@deneb.enyo.de>
Cc: mtk.manpages@gmail.com, Oleg Nesterov <oleg@redhat.com>,
Christian Brauner <christian@brauner.io>,
Jann Horn <jannh@google.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Daniel Colascione <dancol@google.com>,
Joel Fernandes <joel@joelfernandes.org>,
linux-man <linux-man@vger.kernel.org>,
Linux API <linux-api@vger.kernel.org>,
lkml <linux-kernel@vger.kernel.org>
Subject: Re: For review: pidfd_send_signal(2) manual page
Date: Tue, 24 Sep 2019 21:43:38 +0200 [thread overview]
Message-ID: <f4330496-f34e-59f2-6de4-0aafdf639c7a@gmail.com> (raw)
In-Reply-To: <87pnjr9rth.fsf@mid.deneb.enyo.de>
Hello Florian,
On 9/23/19 1:26 PM, Florian Weimer wrote:
> * Michael Kerrisk:
>
>> SYNOPSIS
>> int pidfd_send_signal(int pidfd, int sig, siginfo_t info,
>> unsigned int flags);
>
> This probably should reference a header for siginfo_t.
Thanks. I added: #include <signal.h>
>> ESRCH The target process does not exist.
>
> If the descriptor is valid, does this mean the process has been waited
> for? Maybe this can be made more explicit.
Yes. I added "(i.e., it has terminated and been waited on)".
>> The pidfd_send_signal() system call allows the avoidance of race
>> conditions that occur when using traditional interfaces (such as
>> kill(2)) to signal a process. The problem is that the traditional
>> interfaces specify the target process via a process ID (PID), with
>> the result that the sender may accidentally send a signal to the
>> wrong process if the originally intended target process has termi‐
>> nated and its PID has been recycled for another process. By con‐
>> trast, a PID file descriptor is a stable reference to a specific
>> process; if that process terminates, then the file descriptor
>> ceases to be valid and the caller of pidfd_send_signal() is
>> informed of this fact via an ESRCH error.
>
> It would be nice to explain somewhere how you can avoid the race using
> a PID descriptor. Is there anything else besides CLONE_PIDFD?
Please see my comment in reply to Christian (which will be sent just
after this).
>> static
>> int pidfd_send_signal(int pidfd, int sig, siginfo_t *info,
>> unsigned int flags)
>> {
>> return syscall(__NR_pidfd_send_signal, pidfd, sig, info, flags);
>> }
>
> Please use a different function name. Thanks.
Please see my open question in the thread on pidfd_open().
Thanks for the review, Florian.
Cheers,
Michael
Michael
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
next prev parent reply other threads:[~2019-09-24 19:43 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-23 9:12 For review: pidfd_send_signal(2) manual page Michael Kerrisk (man-pages)
2019-09-23 11:26 ` Florian Weimer
2019-09-23 11:26 ` Florian Weimer
2019-09-23 14:23 ` Christian Brauner
2019-09-24 19:44 ` Michael Kerrisk (man-pages)
2019-09-24 19:57 ` Christian Brauner
2019-09-24 20:07 ` Christian Brauner
2019-09-24 21:00 ` Michael Kerrisk (man-pages)
2019-09-24 21:08 ` Daniel Colascione
2019-09-25 13:46 ` Michael Kerrisk (man-pages)
2019-09-24 21:53 ` Christian Brauner
2019-09-25 13:46 ` Michael Kerrisk (man-pages)
2019-09-25 13:51 ` Florian Weimer
2019-09-25 13:51 ` Florian Weimer
2019-09-25 14:02 ` Michael Kerrisk (man-pages)
2019-09-25 13:53 ` Christian Brauner
2019-09-25 14:29 ` Michael Kerrisk (man-pages)
2019-09-24 19:43 ` Michael Kerrisk (man-pages) [this message]
2019-09-25 1:48 ` Jann Horn
2019-09-23 11:31 ` Daniel Colascione
2019-09-24 19:42 ` Michael Kerrisk (man-pages)
2019-09-23 14:29 ` Christian Brauner
2019-09-23 20:27 ` Michael Kerrisk (man-pages)
2019-09-23 21:27 ` Eric W. Biederman
2019-09-23 21:27 ` Eric W. Biederman
2019-09-24 19:10 ` Michael Kerrisk (man-pages)
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