[PATCH] Avoid unpaired stwcx. on some processors

[Benjamin Herrenschmidt]

> Seems like a "better" (but still ugly) workaround would be to create a
> _new_ reservation to a RA that's unavailable to any userspace process,
> so that they could never do a successful store to it. That way you would
> have stray reservations, but never dangling stwcx:es. No?

Many processors don't compare the reservation address locally. If
there's any valid reservation held by that processor, a subsequent
stwcx. will always succeed. That would make you scheme dangerous :-)

Ben.