Re: [Xen-devel] [v3,11/41] mips: reuse asm-generic/barrier.h

[Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>]

On Tue, Jan 26, 2016 at 3:29 PM, Paul E. McKenney
<paulmck@xxxxxxxxxxxxxxxxxx> wrote:
>
> No trailing data-dependent read, so agreed, no smp_read_barrier_depends()
> needed.  That said, I believe that we should encourage rcu_dereference*()
> or lockless_dereference() instead of READ_ONCE() for documentation
> reasons, though.

I agree that that is likely the right thing to do in pretty much all situations.

In theory, there might be performance situations where we'd want to
actively avoid the smp_read_barrier_depends() inherent in those, but
considering that it's only a performance issue on alpha, and we
probably have all of two or three people using Linux on alpha, it's a
pretty theoretical performance worry.

                  Linus

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