[PATCH 1/4] arm64: topology: Implement basic CPU topology support

[Mark Brown]

On Tue, Feb 11, 2014 at 03:46:04PM +0100, Vincent Guittot wrote:
> On 11 February 2014 15:07, Catalin Marinas <catalin.marinas at arm.com> wrote:

> > As Will said, smp_*mb() do not ensure absolute visibility, only relative
> > to subsequent memory accesses on the same processor. So just placing a
> > barrier at the end of a function does not mean much, it only shows half
> > of the problem it is trying to solve.

> OK, that's probably the shortcut that has been made, we want to drain
> the write buffer to make modification available to other cpus and I
> though smp_wmb and the associated mb(ishst) was there for that
> purpose.

It does also explain where I got to trying to figure out what exactly
the mechanism was!

> > So my proposal is to remove the smp_wmb() from topology.c and add it
> > where it is relevant as described above. If we have some race in
> > topology.c (like for example we may later decide to start more
> > secondaries at the same time), it needs to be solved using spinlocks.

I'll just repost a version dropping them from the topology series and
separately add the barriers elsewhere.  The 32 bit ARM implementation
probably ought to be fixed as well.
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