Date: Thu, 30 Jul 2015 11:03:43 -0700 From: Dennis Ferguson <dennis.c.fergu...@gmail.com>
On 30 Jul, 2015, at 01:53 , Maxime Villard <m...@m00nbsd.net> wrote: > Do we have a magic function that can perform two atomic_swap_ptr() > atomically? I don't think you can have a portable function like that. Not that hard: - On i386, use cmpxchg8b. - On amd64, use cmpxchg16b. - On ll/sc machines, use ll/sc. - On uniprocessor machines, use RAS. - On multiprocessor sparc and anything else not in the above classes, use a hashed locking scheme like we already use for sparc. However, the last case would require making single-word CAS use the hashed locking scheme too even if there is a native single-word CAS, in order to cooperate with double-word CAS -- unless we decide that the two don't have to agree, just as we reject doing both x++ and atomic_inc_uint(&x).
