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>

diff --git a/arch/s390/include/asm/atomic.h b/arch/s390/include/asm/atomic.h
index 117fa5c921c1b035ad8c4a60cc8774cc5022778f..911064aa59b2f25c5c1dc7a7ac846a560ea99b1e 100644 (file)
--- a/arch/s390/include/asm/atomic.h
+++ b/arch/s390/include/asm/atomic.h
@@ -36,7 +36,6 @@
                                                                        \
        typecheck(atomic_t *, ptr);                                     \
        asm volatile(                                                   \
-               __barrier                                               \
                op_string "     %0,%2,%1\n"                             \
                __barrier                                               \
                : "=d" (old_val), "+Q" ((ptr)->counter)                 \
@@ -180,7 +179,6 @@ static inline int __atomic_add_unless(atomic_t *v, int a, int u)
                                                                        \
        typecheck(atomic64_t *, ptr);                                   \
        asm volatile(                                                   \
-               __barrier                                               \
                op_string "     %0,%2,%1\n"                             \
                __barrier                                               \
                : "=d" (old_val), "+Q" ((ptr)->counter)                 \

diff --git a/arch/s390/include/asm/bitops.h b/arch/s390/include/asm/bitops.h
index 66a1cff673531f6cd9f4f0414bf91acc0b499ae6..47bd0878a00670288dc809e9262ec867bcf66ad4 100644 (file)
--- a/arch/s390/include/asm/bitops.h
+++ b/arch/s390/include/asm/bitops.h
@@ -64,7 +64,6 @@
                                                                \
        typecheck(unsigned long *, (__addr));                   \
        asm volatile(                                           \
-               __barrier                                       \
                __op_string "   %0,%2,%1\n"                     \
                __barrier                                       \
                : "=d" (__old), "+Q" (*(__addr))                \