[MUD-Dev] Re: atomic functions

Jon A. Lambert jlsysinc at ix.netcom.com
Wed May 13 17:31:56 New Zealand Standard Time 1998


On  5 May 98, Joel Dillon wrote:
> > Jon A. Lambert <jlsysinc at ix.netcom.com> wrote:
> > >[...]
> > > Trivia note: My terminology "spin-lock" comes from IBM's MVS/ESA 
> > >      architecture.  MVS uses spin-locking in its page locking scheme 
> > >      to implement shared memory.  
> 
>   I was under the impression that a spinlock (from Posix threads/parallel
> processing terminology) was a mutex which was locked by repeatedly trying
> to grab the mutex for a short period of time (useful only on parallel
> processing machines where grabbing a new processor outweighs the extra
> CPU cycles expended on the old one).
> 

I'm not familiar with Posix, although I can tell you that the term is 
quite old in the mainframe world.  Where it really originated, I have 
no idea.  My introduction to it was not through Posix.  Your 
definition of spinlock from Posix is quite similar conceptually to 
the mainframe one, except the IBM is peculiar to shared memory 
rather than shared CPU.  We don't often use the terms mutex, 
semaphore, thread, etc. outside of mainframe C application 
programming.  They are implemented, but the underlying mechanisms 
have a terminology of their own at the operating system level.

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