Re: pserialize(9) vs. TAILQ

[Taylor R Campbell <campbell+netbsd-tech-kern%mumble.net@localhost>]

   Date: Fri, 21 Nov 2014 18:25:02 +0800
   From: Dennis Ferguson <dennis.c.ferguson%gmail.com@localhost>

   Beyond the Alpha-barrier, he only thing I find lacking about the membar_*()
   API is maybe a set of functions that would eliminate the #ifndef/#endif
   around

       #ifndef __HAVE_ATOMIC_AS_MEMBAR
                   membar_foo();
       #endif

   repeated over and over when synchronization is done via atomic_ops(3).

I've been meaning to add preatomic_membar_foo/postatomic_membar_foo to
address this, since finding typos in the cpp conditional that went
undetected for years.

Not sure it's necessary to distinguish the pre/post cases -- Linux
does with smp_mb__before_atomic/smp_mb__after_atomic, but I'm not sure
that distinction is needed for all our membar_foos, and I haven't
taken the time to research the situation adequately.