Re: [RFC PATCH 01/20] asm-generic/mmiowb: Add generic implementation of mmiowb() tracking

[Linus Torvalds]

On Tue, Feb 26, 2019 at 10:33 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> Arguably we could fix that for __this_cpu_xchg(), which isn't IRQ-safe.

Yeah, I guess x86 _should_ really do __this_cpu_xchg() as just a
read-write pair.

In general, a read-write pair is probably always the right thing to
do, and the only reason we can't just do it in an
architecture-independent way is that we'd want to avoid doing the
address generation twice (for architectures where that is an issue).

                  Linus