Re: Why is __cpu_simple_lock_t an unsigned char?

[Matt Thomas <matt%3am-software.com@localhost>]

On Nov 6, 2008, at 12:35 AM, Heikki Krogerus wrote:

> Matt Thomas wrote:
> > On Nov 5, 2008, at 11:21 PM, Heikki Krogerus wrote:
> >
> > > This probably is a silly quistion, I know, but how should the
> > > ldrex/strex be
> > > handled in the future? Our ARM1136JF-S does not seem to support
> > > ldrexb/strexb
> > > instructions.
> > >
> > > Thumb does not support the swp instruction.
> >
> > because armv4 and later have swpb (swap byte).
>
> but the ARM architecture reference manual mentions that "From  
> ARMv6, use of SWP
> and SWPB instructions is deprecated" and from the comments in
> sys/arch/arm/include/mutex.h I figured that ldrex/strex will be  
> added eventually.

Actually, they are already in use.

You can emulate ldrexb/strexb with ldrex/strex so that isn't really a  
problem.