Subject: Re: memsync/cacheflush proposals: status
To: None <,>
From: Wolfgang Solfrank <>
List: tech-userlevel
Date: 02/09/1999 16:08:21

one minor nit:

> - I did a bit code and manual browsing myself and noticed that mmap() can 
> be told to make the region semaphore-safe, which would make userland
> memory barriers for userland semaphores (as implemented using CAS/CAS2 on m68k
> or maybe the reservation stuff on PPC) unneeded. Multi-CPU machines that
> do NOT provide coherency in hardware should be thr^H^H^Htaught to make share
> regions uncached, maybe... you'll have a performance penalty in either case.

If you are looking for a semaphore mechanism on PPC independent from the
particular implementation of the cpu, there is _no_ possibility to do
this without the use of lwarx/stwcx..  No, making the shared regions
uncached/guarded etc. isn't sufficient.

ws@TooLs.DE     (Wolfgang Solfrank, TooLs GmbH) 	+49-228-985800