linux-kernel - Re: futex(2) man page update help request

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Message-ID: <CF9A2E34.90E56%dvhart@linux.intel.com>
Date:	Thu, 15 May 2014 08:43:04 -0700
From:	Darren Hart <dvhart@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Carlos O'Donell <carlos@...hat.com>
CC:	<mtk.manpages@...il.com>, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, Jakub Jelinek <jakub@...hat.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>,
	Linux API <linux-api@...r.kernel.org>
Subject: Re: futex(2) man page update help request

On 5/15/14, 1:13, "Peter Zijlstra" <peterz@...radead.org> wrote:

>On Wed, May 14, 2014 at 04:23:38PM -0400, Carlos O'Donell wrote:
>> On 05/14/2014 03:03 PM, Michael Kerrisk (man-pages) wrote:
>> >> 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*".)
>> 
>> I fully agree with Michael here.
>> 
>> The futex() syscall was never exposed to userspace specifically because
>> it was an interface we did not want to support forever with a stable
>>ABI.
>> The futex() syscall is an implementation detail that is shared between
>> the kernel and the writers of core runtimes for Linux.
>
>That ship has sailed.. for one we must always support old glibc which
>uses the futex() syscall, and secondly there are known other programs
>that actually use the futex syscall.
>
>So that's really a non-argument, we're hard tied to the ABI.

Indeed. This is specifically why FUTEX_REQUEUE still exists (despite it's
bugs) when only FUTEX_CMP_REQUEUE should ever be used in new programs.


-- 
Darren Hart					Open Source Technology Center
darren.hart@...el.com				            Intel Corporation



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