atomic, arch: Audit atomic_{read,set}()

This patch makes sure that atomic_{read,set}() are at least
{READ,WRITE}_ONCE().

We already had the 'requirement' that atomic_read() should use
ACCESS_ONCE(), and most archs had this, but a few were lacking.
All are now converted to use READ_ONCE().

And, by a symmetry and general paranoia argument, upgrade atomic_set()
to use WRITE_ONCE().

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: james.hogan@imgtec.com
Cc: linux-kernel@vger.kernel.org
Cc: oleg@redhat.com
Cc: will.deacon@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/ia64/include/asm/atomic.h

@@ -21,11 +21,11 @@
 #define ATOMIC_INIT(i)		{ (i) }
 #define ATOMIC64_INIT(i)	{ (i) }
 
-#define atomic_read(v)		ACCESS_ONCE((v)->counter)
-#define atomic64_read(v)	ACCESS_ONCE((v)->counter)
+#define atomic_read(v)		READ_ONCE((v)->counter)
+#define atomic64_read(v)	READ_ONCE((v)->counter)
 
-#define atomic_set(v,i)		(((v)->counter) = (i))
-#define atomic64_set(v,i)	(((v)->counter) = (i))
+#define atomic_set(v,i)		WRITE_ONCE(((v)->counter), (i))
+#define atomic64_set(v,i)	WRITE_ONCE(((v)->counter), (i))
 
 #define ATOMIC_OP(op, c_op)						\
 static __inline__ int							\