Re: [RFC][PATCH 05/31] locking,arm64: Implement atomic{,64}_fetch_{add,sub,and,andnot,or,xor}{,_relaxed,_acquire,_release}()

From: Will Deacon
Date: Fri Apr 22 2016 - 10:23:28 EST

On Fri, Apr 22, 2016 at 11:04:18AM +0200, Peter Zijlstra wrote:
> Implement FETCH-OP atomic primitives, these are very similar to the
> existing OP-RETURN primitives we already have, except they return the
> value of the atomic variable _before_ modification.
> This is especially useful for irreversible operations -- such as
> bitops (because it becomes impossible to reconstruct the state prior
> to modification).

The LSE bits will take me some time, but you're also missing some stuff
for the LL/SC variants. Fixup below.