Process synchronize with CAS

Hi, everyone
     I am interested in the interface of linux. As we all know, there
is CAS way to accomplish the lockless ring buffer  with the kernel .
The kernel api can realize the datastruct Such as
__sync_fetch_and_add   type __sync_fetch_and_sub (type  * ptr, type
value, ...) and so on
But I find the limitation that this CAS  is work good for the  thread
model rather than Process model .  I want to create a shared Memory
and use mmap API  to mount this shared memory into  producter and
consumer process. What should I do to realize the synchronization
using the CAS algorithm . Are there have any API can over cross
Multi-Process just like the thread model? I would appreciate that
someone can provide the information for this email. Thank you!

Regards,
Jack