svn commit: r336025 - in head/sys: amd64/include i386/include

[Peter Jeremy]

On 2018-Jul-06 09:47:00 -0600, Warner Losh <imp at bsdimp.com> wrote:
>On UP systems, these additional opcodes are harmless. They take a few extra
>cycles (since they lock an uncontested bus) and add a couple extra memory
>barriers (which will be NOPs). On MP systems, atomics now work by default.

Atomics in modules used to work by default (at least on x86) - they were
explicitly not inlined so that modules on UP systems didn't have to include
the lock and barrier instructions that were very expensive on some systems
20 years ago.  That said, those systems are (hopefully) all dead now so
moving to inlining SMP versions of atomic operations in modules is probably
the correct decision now.

-- 
Peter Jeremy
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