Re: [PATCH 4/4] locking: Introduce smp_cond_acquire()

[Peter Zijlstra]

On Mon, Nov 02, 2015 at 08:36:49PM +0000, David Howells wrote:
> Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> 
> > > +       smp_read_barrier_depends(); /* ctrl */  \
> > > +       smp_rmb(); /* ctrl + rmb := acquire */  \
> 
> Doesn't smp_rmb() imply an smp_read_barrier_depends() anyway?  In
> memory-barriers.txt, it says:
> 
>      Read memory barriers imply data dependency barriers, and so can
>      substitute for them.

Yes, I noted that in a follow up email, Alpha implements both as MB. So
just the smp_rmb() is sufficient.

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