atomic operations in user space

[Liu Dave-r63238]

> > 2) These mutexes are based on futexes which requires atomic 
> > operations in userspace. These are available on most architectures.
Look at
> > the glibc code in
> > nptl/sysdeps/unix/sysv/linux/powerpc/lowlevellock.h for instance.
> > Use that and your PPC manual to implement your atomic operations.
> 
> No matter semaphore or futex, it uses system calls to kernel.  And the
> true atomic operation is in kernel not user space.  Maybe 
> it's feasible
> for other architectures to do atomic operations directly in 
> user space.
> IMHO, not for powerpc.

Are you meaning that we didn't do atomic operations directly in user
space
on powerpc platform ?

-DAve