From: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
To: Darren Hart <dvhart@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
Jakub Jelinek <jakub@redhat.com>,
"linux-man@vger.kernel.org" <linux-man@vger.kernel.org>,
lkml <linux-kernel@vger.kernel.org>,
Davidlohr Bueso <davidlohr.bueso@hp.com>,
Arnd Bergmann <arnd@arndb.de>,
Steven Rostedt <rostedt@goodmis.org>,
Peter Zijlstra <peterz@infradead.org>,
Linux API <linux-api@vger.kernel.org>,
"Carlos O'Donell" <carlos@redhat.com>
Subject: Re: futex(2) man page update help request
Date: Wed, 14 May 2014 21:03:02 +0200 [thread overview]
Message-ID: <CAKgNAkh+PWzT2SByaLk_OtiAXeZSkWoMgu+ivDOt1dTWVtaatQ@mail.gmail.com> (raw)
In-Reply-To: <CF98E3EF.90564%dvhart@linux.intel.com>
Hi Darren,
On Wed, May 14, 2014 at 6:18 PM, Darren Hart <dvhart@linux.intel.com> wrote:
> On 5/14/14, 3:35, "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
> wrote:
>
>>[So, some futex recent discussions remind me I should make this request]
>>
>>Hello all (especially those in the To:, namely Thomas, Darren, Ingo,
>>Jakub),
>>
>>The futex man pages:
>>http://man7.org/linux/man-pages/man2/futex.2.html
>>http://man7.org/linux/man-pages/man7/futex.7.html
>>are currently in a sorry state. I'm by no means convinced that all of the
>>futex operations described there are explained fully and correctly. And
>>probably not all error cases for each operation are properly documented.
>>I'd be very happy if some folk could review those pages and send me
>>corrections (Git:
>>http://git.kernel.org/pub/scm/docs/man-pages/man-pages).
>>
>>But worse, a number of futex operations remain undocumented in futex(2)
>>(see the list below).
>>
>>I am aware of Documentation/pi-futex.txt and
>>Documentation/futex-requeue-pi.txt. However, both of those documents
>>are rather thin on details / explain what certain FUTEX_* operations are
>>used for rather than what they do / focus on the implementation, rather
>>than the semantics.
>>
>>What I would like is that the futex(2) page documenta each one of
>>these operations with a focus on the semantics in a way that might be
>>useful to writers of library functions or those who simply wish to
>>better understand (from a user-space perspective) what futexes are
>>and how they are used. However, I don't have the knowledge to do
>>this well in any reasonable time.
>>
>>Would the folk in the To: list (or anyone else who is knowledgeable)
>>be willing to write patches
>>(Git: http://git.kernel.org/pub/scm/docs/man-pages/man-pages )
>>or just supply me with some raw text that documents these currently
>>undocumented futex operations, in the manner suggested?
>
> Yes, I'll be glad to help.
Thanks!
> However, unless I'm sorely mistaken, the larger problem is that glibc
> removed the futex() call entirely, so these man pages don't describe
I don't think futex() ever was in glibc--that's by design, and
completely understandable: no user-space application would want to
directly use futex(). (BTW, I mispoke in my earlier mail when I said I
wanted documentation suitable for "writers of library functions" -- I
meant suitable for "writers of *C library*".)
> something users even have access to anymore. I had to revert to calling
> the syscalls directly in the futextest test suite because of this:
>
> http://git.kernel.org/cgit/linux/kernel/git/dvhart/futextest.git/tree/inclu
> de/futextest.h#n67
>
>
> Which basically defines:
>
> #define futex(uaddr, op, val, timeout, uaddr2, val3, opflags) \
> syscall(SYS_futex, uaddr, op | opflags, val, timeout, uaddr2, val3)
>
>
> Adding Carlos for his perspective.
>
> If I'm wrong, or we can restore the futex() call, great. If not... Should
> we keep the man-pages and document it as syscall(SYS_futex, ..., op, ...) ?
We should keep the man page ;-). I just need to add some words to
point out the use of syscall(). Mostly though, I'm interested in
getting documentation of the operations listed below :-).
Cheers,
Michael
>> commit 4732efbeb997189d9f9b04708dc26bf8613ed721
>> Author: Jakub Jelinek <jakub@redhat.com>
>> Date: Tue Sep 6 15:16:25 2005 -0700
>> See also https://bugzilla.kernel.org/show_bug.cgi?id=14303
>>
>>2.6.18 adds priority inheritance support:
>>FUTEX_LOCK_PI, FUTEX_UNLOCK_PI, and FUTEX_TRYLOCK_PI.
>> commit c87e2837be82df479a6bae9f155c43516d2feebc
>> Author: Ingo Molnar <mingo@elte.hu>
>> Date: Tue Jun 27 02:54:58 2006 -0700
>>
>> commit e2970f2fb6950183a34e8545faa093eb49d186e1
>> Author: Ingo Molnar <mingo@elte.hu>
>> Date: Tue Jun 27 02:54:47 2006 -0700
>>
>> See Documentation/pi-futex.txt
>>
>>2.6.25 adds FUTEX_WAKE_BITSET, FUTEX_WAIT_BITSET
>> commit cd689985cf49f6ff5c8eddc48d98b9d581d9475d
>> Author: Thomas Gleixner <tglx@linutronix.de>
>> Date: Fri Feb 1 17:45:14 2008 +0100
>>
>>2.6.31 adds FUTEX_WAIT_REQUEUE_PI, FUTEX_CMP_REQUEUE_PI
>> commit 52400ba946759af28442dee6265c5c0180ac7122
>> Author: Darren Hart <dvhltc@us.ibm.com>
>> Date: Fri Apr 3 13:40:49 2009 -0700
>>
>> commit ba9c22f2c01cf5c88beed5a6b9e07d42e10bd358
>> Author: Darren Hart <dvhltc@us.ibm.com>
>> Date: Mon Apr 20 22:22:22 2009 -0700
>>
>> See Documentation/futex-requeue-pi.txt
>>
>>Thanks,
>>
>>Michael
>>
>>
>>--
>>Michael Kerrisk
>>Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
>>Linux/UNIX System Programming Training: http://man7.org/training/
>>
>
>
> --
> Darren Hart Open Source Technology Center
> darren.hart@intel.com Intel Corporation
>
>
>
--
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:[~2014-05-14 19:03 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-14 10:35 futex(2) man page update help request Michael Kerrisk (man-pages)
2014-05-14 16:18 ` Darren Hart
2014-05-14 19:03 ` Michael Kerrisk (man-pages) [this message]
2014-05-14 19:59 ` Darren Hart
2014-05-14 20:23 ` Carlos O'Donell
2014-05-14 20:44 ` Andy Lutomirski
2014-05-14 23:34 ` Thomas Gleixner
2014-05-15 3:12 ` Carlos O'Donell
2014-05-15 4:49 ` Michael Kerrisk (man-pages)
2014-05-15 4:53 ` Michael Kerrisk (man-pages)
2014-05-15 14:14 ` Thomas Gleixner
2014-05-15 20:19 ` Michael Kerrisk (man-pages)
2014-08-04 14:46 ` Carlos O'Donell
2014-05-15 20:35 ` Darren Hart
2015-01-15 15:12 ` Michael Kerrisk (man-pages)
2015-01-17 1:33 ` Darren Hart
2015-01-17 9:16 ` Michael Kerrisk (man-pages)
2015-01-17 19:26 ` Darren Hart
2015-01-18 10:18 ` Michael Kerrisk (man-pages)
2015-01-15 15:10 ` Michael Kerrisk (man-pages)
2015-01-15 22:23 ` Thomas Gleixner
2015-01-16 15:17 ` Michael Kerrisk (man-pages)
2015-01-16 15:20 ` Thomas Gleixner
2015-01-16 20:54 ` Michael Kerrisk (man-pages)
2015-01-17 0:46 ` Darren Hart
2015-01-19 10:45 ` Thomas Gleixner
2015-01-19 14:07 ` Michael Kerrisk (man-pages)
2015-01-23 18:19 ` Torvald Riegel
2015-01-24 10:05 ` Thomas Gleixner
2015-01-24 12:58 ` Torvald Riegel
2015-01-24 16:25 ` Thomas Gleixner
2015-01-17 0:56 ` Davidlohr Bueso
2015-01-17 1:11 ` Darren Hart
2015-01-23 18:29 ` Torvald Riegel
2015-01-24 11:35 ` Thomas Gleixner
2015-01-24 13:12 ` Torvald Riegel
2015-01-27 7:48 ` Michael Kerrisk (man-pages)
2015-02-05 19:57 ` Darren Hart
2014-05-15 8:13 ` Peter Zijlstra
2014-05-15 15:43 ` Darren Hart
2014-05-15 8:14 ` Peter Zijlstra
2014-05-15 13:18 ` Carlos O'Donell
2014-05-15 13:22 ` Peter Zijlstra
2014-05-15 13:49 ` Michael Kerrisk (man-pages)
2014-05-15 13:55 ` Peter Zijlstra
2014-05-15 14:39 ` Carlos O'Donell
2014-05-15 15:11 ` Peter Zijlstra
2014-05-14 20:56 ` Davidlohr Bueso
2014-05-14 21:03 ` Darren Hart
2014-05-14 22:21 ` Paul E. McKenney
2014-05-15 0:28 ` H. Peter Anvin
2014-05-15 0:35 ` Andy Lutomirski
2014-05-15 0:41 ` H. Peter Anvin
2014-05-15 19:10 ` Carlos O'Donell
2014-05-14 21:05 ` Davidlohr Bueso
2014-05-15 15:15 ` Joseph S. Myers
2014-05-15 0:18 ` H. Peter Anvin
2014-05-15 5:21 ` Darren Hart
2014-05-15 8:23 ` Peter Zijlstra
2014-05-15 13:46 ` Michael Kerrisk (man-pages)
2014-05-15 14:59 ` H. Peter Anvin
2014-05-15 15:42 ` chrubis
2014-05-15 15:52 ` H. Peter Anvin
2014-05-15 16:01 ` chrubis
2014-05-15 16:07 ` H. Peter Anvin
2014-05-15 16:17 ` chrubis
2014-05-15 16:56 ` H. Peter Anvin
2014-05-15 17:06 ` chrubis
2014-05-15 15:47 ` Darren Hart
2014-05-15 15:35 ` chrubis
2014-05-15 15:28 ` chrubis
2014-05-15 15:40 ` Steven Rostedt
2014-05-15 16:14 ` Darren Hart
2014-05-15 16:30 ` chrubis
2014-05-15 18:17 ` Darren Hart
2014-05-15 19:05 ` chrubis
2014-05-15 19:38 ` Darren Hart
2014-08-11 10:19 ` chrubis
2014-11-26 13:41 ` Cyril Hrubis
2015-02-16 13:14 ` Cyril Hrubis
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