Re: Futex manpages out of date

[Darren Hart <dvhltc-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>]

Petr Baudis wrote:
> On Fri, Jan 15, 2010 at 06:11:24PM +0100, Peter Zijlstra wrote:
>> On Fri, 2010-01-15 at 08:58 -0800, Darren Hart wrote:
>>> The futex man-pages (2,7) from version 3.15-1 and at least a few earlier
>>> versions are considerably out of date with respect to the current
>>> implementation. They don't document newer op codes, such as:
>>>
>>> FUTEX_WAIT_BITSET
>>> FUTEX_WAKE_BITSET
>>> FUTEX_WAKE_OP
>>> FUTEX_LOCK_PI
>>> FUTEX_UNLOCK_PI
>>> FUTEX_WAIT_REQUEUE_PI
>>> FUTEX_CMP_REQUEUE_PI
>>>
>>> These new wait op codes now use absolute timeouts, while the original
>>> FUTEX_WAIT uses a relative timeout. Lastly, and most importantly, glibc
>>> has removed the futex() wrapper to syscall(SYS_futex, ...). With that in
>>> mind, would people prefer that we simply remove the futex man-pages
>>> (2,7)?
>> A readable text about the interaction between the futex value and the
>> various futex ops and how to build proper locking primitives with them
>> would be helpful I think, however doing that in the form of a locking
>> library (as has been suggested at KS) seems plenty fine to me.
>>
>> Readable code is much better than rambling English at conveying this
>> stuff.
> 
> http://people.redhat.com/drepper/futex.pdf is pretty good description,
> unfortunately also outdated by now. Perhaps it would be interesting to
> convert this into some kind of wiki form with Ulrich's permission?

Does anyone know what is being done documentation-wise with other 
syscalls? I believe glibc has removed other wrappers as well. In my 
opinion the best place for this is in the linux kernel Documentation 
directory. I have already documented requeue_pi there. Ulrich's paper 
would server as an excellent starting point for a sysfutex.txt or 
futex_usage.txt file.

Ulrich, do you have a preference or any requirements on how your work is 
used?

-- 
Darren Hart
IBM Linux Technology Center
Real-Time Linux Team
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