From: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: "Carlos O'Donell" <carlos@redhat.com>,
Darren Hart <dvhart@linux.intel.com>, 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>
Subject: Re: futex(2) man page update help request
Date: Thu, 15 May 2014 06:53:38 +0200 [thread overview]
Message-ID: <CAKgNAkjQ5Dd_U9OojXdgeforpRevvPHNFAw99kBFPCwHgf7Ggg@mail.gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.02.1405150121230.6261@ionos.tec.linutronix.de>
Hi Thomas,
On Thu, May 15, 2014 at 1:34 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
> On Wed, 14 May 2014, 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.
>
> Nonsense.
>
> If we change that interface (aside of adding functionality or some new
> error return) it would break the world and some more, simply because
> out of the blue glibc-2.xx would stop to work on linux-3.yy.
>
> Aside of that the futex syscall is used as a bare interface without
> any glibc interaction:
>
> - It's handy to implement user space wait queues
>
> - It's (ab)used in very interesting ways by data base apps
>
> - It's (ab)used by some Java monstrosities.
Thanks for the education about user-space uses of futexes. I was unaware.
> Nothing you care about and you really don't want to see the gory
> details, but you have to accept that there is an universe which is
> happy to deal with the raw syscalls instead of going through some ill
> defined posix interfaces.
And that universe would love to have your documentation of
FUTEX_WAKE_BITSET and FUTEX_WAIT_BITSET ;-),
Cheers,
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:[~2014-05-15 4:54 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)
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) [this message]
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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