>>> I know, but I'm a userland program, so I need a kernel service.
>> No...you may need an architecture-dependent service, but that
>> doesn't necessarily mean a kernel service.  A routine [from] an OS
>> library such as libc might do as well.
> I see.  I've been assuming that atomic memory operations are
> privileged instructions available only to the kernel.  You and Jason
> are telling me that assumption doesn't hold across CPU architectures.

Right.  Sometimes it does, but sometimes not (eg, the VAX has some
half-dozen instructions which are totally nonprivileged but are
specifically defined to interlock properly against other CPUs in a MP
system, and which cannot be interrupted partly done even on when UP,
and which are thus useful in cases like this).

/~\ The ASCII				der Mouse
\ / Ribbon Campaign
 X  Against HTML	       mouse@rodents.montreal.qc.ca
/ \ Email!	     7D C8 61 52 5D E7 2D 39  4E F1 31 3E E8 B3 27 4B