Re: implementing Futex

Arnd Bergmann
2009-08-14T13:33:22Z

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.