Date:	Wed, 14 May 2014 12:35:17 +0200
From:	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	Jakub Jelinek <jakub@...hat.com>,
	Darren Hart <dvhart@...ux.intel.com>
CC:	mtk.manpages@...il.com,
	"linux-man@...r.kernel.org" <linux-man@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Davidlohr Bueso <davidlohr.bueso@...com>,
	Arnd Bergmann <arnd@...db.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Linux API <linux-api@...r.kernel.org>
Subject: futex(2) man page update help request

[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?

The operations for which documentation is currently missing are:

2.6.14 adds FUTEX_WAKE_OP
    commit 4732efbeb997189d9f9b04708dc26bf8613ed721
    Author: Jakub Jelinek <jakub@...hat.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@...e.hu>
    Date:   Tue Jun 27 02:54:58 2006 -0700

    commit e2970f2fb6950183a34e8545faa093eb49d186e1
    Author: Ingo Molnar <mingo@...e.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@...utronix.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@...ibm.com>
    Date:   Fri Apr 3 13:40:49 2009 -0700

    commit ba9c22f2c01cf5c88beed5a6b9e07d42e10bd358
    Author: Darren Hart <dvhltc@...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/
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