linux-kernel - Re: implementing Futex

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Message-Id: <200908141533.16714.arnd@arndb.de>
Date:	Fri, 14 Aug 2009 15:33:16 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Michael Schnell <mschnell@...ino.de>
Cc:	linux-kernel@...r.kernel.org,
	Mike Frysinger <vapier.adi@...il.com>,
	Paul Mundt <lethal@...ux-sh.org>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Ingo Molnar <mingo@...e.hu>, Jakub Jelinek <jakub@...hat.com>,
	Thomas Chou <thomas@...ron.com.tw>
Subject: Re: implementing Futex

On Friday 14 August 2009, Michael Schnell wrote:
> Arnd Bergmann wrote:
> > The man page says that the last parameter is ignored for op=FUTEX_WAKE,
> > which is correct. The code that you were looking at however is for
> > of=FUTEX_WAKE_OP, which is not documented as of manpages-3.22.
> > 
> > It was added by Jakub back in 2005, but if he wrote a documentation
> > for it, it never went into the man pages package. On a similar
> > note, Ingo also added other futex operations that are not documented
> > yet.
> > 
> 
> Thus in any documented software, the quite complex stuff in
> "futex_atomic_op_inuser", which is provided in several different
> "futex.h" files for all those architectures never is used ?

No, my point was that futex_atomic_op_inuser is indeed used
correctly, it's just not documented.
See http://lwn.net/Articles/148830/ for the initial posting

> Is there any viable use for this ?

glibc heavily uses it for the pthreads implementation.
 
> Would it not be appropriate either to do a documentation or to remove it ?

Adding documentation, yes.

	Arnd <><
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