Force reading of *in_sync in while loop. Loops where the content that
is checked for is changed by a different cpu always should have some
sort of barrier() semantics.
Otherwise this might lead to very subtle bugs.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>