arch: Prepare for smp_mb__{before,after}_atomic()

Since the smp_mb__{before,after}*() ops are fundamentally dependent on
how an arch can implement atomics it doesn't make sense to have 3
variants of them. They must all be the same.

Furthermore, the 3 variants suggest they're only valid for those 3
atomic ops, while we have many more where they could be applied.

So move away from
smp_mb__{before,after}_{atomic,clear}_{dec,inc,bit}() and reduce the
interface to just the two: smp_mb__{before,after}_atomic().

This patch prepares the way by introducing default implementations in
asm-generic/barrier.h that default to a full barrier and providing
__deprecated inlines for the previous 6 barriers if they're not
provided by the arch.

This should allow for a mostly painless transition (lots of deprecated
warns in the interim).

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/n/tip-wr59327qdyi9mbzn6x937s4e@git.kernel.org
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "Chen, Gong" <gong.chen@linux.intel.com>
Cc: John Sullivan <jsrhbz@kanargh.force9.co.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mauro Carvalho Chehab <m.chehab@samsung.com>
Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: linux-arch@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

3 files changed, 10 insertions, 14 deletions

diff --git a/include/asm-generic/atomic.h b/include/asm-generic/atomic.h
index 33bd2de3bc1e..9c79e7603459 100644
--- a/include/asm-generic/atomic.h
+++ b/include/asm-generic/atomic.h
@@ -16,6 +16,7 @@
 #define __ASM_GENERIC_ATOMIC_H
 
 #include <asm/cmpxchg.h>
+#include <asm/barrier.h>
 
 #ifdef CONFIG_SMP
 /* Force people to define core atomics */
@@ -182,11 +183,5 @@ static inline void atomic_set_mask(unsigned int mask, atomic_t *v)
 }
 #endif
 
-/* Assume that atomic operations are already serializing */
-#define smp_mb__before_atomic_dec()     barrier()
-#define smp_mb__after_atomic_dec()      barrier()
-#define smp_mb__before_atomic_inc()     barrier()
-#define smp_mb__after_atomic_inc()      barrier()
-
 #endif /* __KERNEL__ */
 #endif /* __ASM_GENERIC_ATOMIC_H */
diff --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h
index 6f692f8ac664..1402fa855388 100644
--- a/include/asm-generic/barrier.h
+++ b/include/asm-generic/barrier.h
@@ -62,6 +62,14 @@
 #define set_mb(var, value)  do { (var) = (value); mb(); } while (0)
 #endif
 
+#ifndef smp_mb__before_atomic
+#define smp_mb__before_atomic() smp_mb()
+#endif
+
+#ifndef smp_mb__after_atomic
+#define smp_mb__after_atomic()  smp_mb()
+#endif
+
 #define smp_store_release(p, v)                                         \
 do {                                                                    \
         compiletime_assert_atomic_type(*p);                             \
diff --git a/include/asm-generic/bitops.h b/include/asm-generic/bitops.h
index 280ca7a96f75..dcdcacf2fd2b 100644
--- a/include/asm-generic/bitops.h
+++ b/include/asm-generic/bitops.h
@@ -11,14 +11,7 @@
 
 #include <linux/irqflags.h>
 #include <linux/compiler.h>
-
-/*
- * clear_bit may not imply a memory barrier
- */
-#ifndef smp_mb__before_clear_bit
-#define smp_mb__before_clear_bit()      smp_mb()
-#define smp_mb__after_clear_bit()       smp_mb()
-#endif
+#include <asm/barrier.h>
 
 #include <asm-generic/bitops/__ffs.h>
 #include <asm-generic/bitops/ffz.h>