Fast User Space Mutexes (aka Futexes)

Bill Huey (hui) billh at
Tue Oct 21 16:52:12 PDT 2003

On Tue, Oct 21, 2003 at 04:05:04PM +0100, Hiten Pandya wrote:
> Hi Gang,
> Sinces the day when Matt was interviewed by the SlashNET people, a 
> couple of questions arised as to the implementation of Futexes for the 
> new libcr which is going to be written.
> I am sending this mail as an opening to this discussion.  Hopefully, 
> some of the Linux seniors scanning this lists (Rik et al) will provide 
> some comments and suggestions on this topic.
> IMHO, from the way Futexes work, it would be great to have an 
> implementation of it for DragonFly.  For those of you wondering what 
> Futexes are exactly, please refer to [1], as thats the most complete 
> documented information I could find, apart from the Ottawa proceedings 
> (Rusty Russell).
> [1] -

Better documentation on how it's used and some implementation issues with
glibc. The problem with futex's in the context of dfBSD is that it's
used for their 1:1 threading model, which is different than the M:N
stuff that's being done recently. I think it's essential to think about
the application of this mechanism and how it will fit into the grand
scheme of things and/or its specific use before throwing it in randomly.


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