tree e7888be8d1d81987e5acc648b2c52d9bac5e41ff
parent 26760fc19a7e663e4f49d586aca6740fb21d887d
author Boqun Feng <boqun.feng@gmail.com> 1450189457 +0800
committer Michael Ellerman <mpe@ellerman.id.au> 1455714699 +1100

powerpc: atomic: Implement acquire/release/relaxed variants for cmpxchg

Implement cmpxchg{,64}_relaxed and atomic{,64}_cmpxchg_relaxed, based on
which _release variants can be built.

To avoid superfluous barriers in _acquire variants, we implement these
operations with assembly code rather use __atomic_op_acquire() to build
them automatically.

For the same reason, we keep the assembly implementation of fully
ordered cmpxchg operations.

However, we don't do the similar for _release, because that will require
putting barriers in the middle of ll/sc loops, which is probably a bad
idea.

Note cmpxchg{,64}_relaxed and atomic{,64}_cmpxchg_relaxed are not
compiler barriers.

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>