[S390] atomic ops: add effecient atomic64 support for 31 bit

Use compare double and swap to implement efficient atomic64 ops for 31 bit.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2 files changed