673
Subj : Re: User-level thread library/package for Linux
To   : comp.programming.threads
From : David Butenhof
Date : Mon Sep 19 2005 01:34 pm

50295@web.de wrote:
>>> Does anyone know where I can find a user-level thread library/package
>>> for Linux?
>> Do you mean a M:1 implementation model? A possibility would be to use
>> GNU Pth:
>> http://www.gnu.org/software/pth/
> 
> Thanks.
> 
>> Note howewer that this implementation uses a non-preemptive scheduler.
> 
> This could be a problem because my intention I'm trying to illustrate
> (preemptive) scheduling with a user-level threads.
> 
> Do user-level thread libraries support preemptive scheduling? I'm still
> looking for one.

It's been done. But if you want preemptive scheduling done right, you 
need to have kernel support. It may be "1:1" kernel support like Linux, 
or "M:N" kernel support like Tru64 UNIX -- but anyone who thinks they 
can do a reasonable job (for anything but small scale demonstration 
purposes) without kernel support is just wrong. We spent an enormous 
amount of time on this in the original DCE threads implementation, and 
it was an emormous mess and continual maintenance problem for what at 
best might be considered an 80% solution.

If all you're looking for is that "small scale demonstration", maybe you 
could find something -- but what's the point? If you have any interest 
in real use, forget about it.

-- 
Dave Butenhof, David.Butenhof@hp.com
HP Utility Pricing software, POSIX thread consultant
Manageability Solutions Lab (MSL), Hewlett-Packard Company
110 Spit Brook Road, ZK2/3-Q18, Nashua, NH 03062

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