tree 5fa860d7cbf09ccc0d3096d5986867b5bfc6b86f
parent b5a6b71b1901b9ca495f669c9ad86f2181960aba
author Martin Schwidefsky <schwidefsky@de.ibm.com> 1443446846 +0200
committer Martin Schwidefsky <schwidefsky@de.ibm.com> 1444825927 +0200

s390/barrier: remove unnecessary serialization in atomics and bitops

The principles of operation states reads are in order, writes are in
order, writes can be reordered after reads, but no reads can be
reordered after writes.

The atomic and bitops variantes for z196 use the interlocked-access
facility instructions with a memory barrier before and after the
instruction. Because of the memory ordering the first barrier is
unnecessary and can be removed.

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