[RFC] arm: Add for atomic half word exchange

[Russell King - ARM Linux]

On Tue, May 19, 2015 at 11:20:11AM +0000, Sarbojit Ganguly wrote:
> Yes, I will try to do that. OTOH, I saw that  there was a discussion on
> removal of bad_xchg() altogether. Perhaps that approach be better than
> adding this half word exchange?

The only possibility for removal of __bad_xchg() is to remove it's
_definition_ only, not its callsite, so that we get a _link_ time
error for use cases we don't support.

Removing its callsite leaves us open to code malfunction: xchg()
effectively becomes a no-op for sizes which are not supported, and
that's a _very_ bad thing to happen.

-- 
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.