svn commit: r228222 - head/sys/sparc64/include

[Marius Strobl]

Author: marius
Date: Sat Dec  3 13:51:57 2011
New Revision: 228222
URL: http://svn.freebsd.org/changeset/base/228222

Log:
  Revert r225889 a bit. While it's correct that in total store order there's
  no need to additionally add CPU memory barriers to the acquire variants of
  atomic(9), these are documented to also include compiler memory barriers.
  So add the latter, which were previously included by using membar(), back.

Modified:
  head/sys/sparc64/include/atomic.h

Modified: head/sys/sparc64/include/atomic.h
==============================================================================
--- head/sys/sparc64/include/atomic.h	Sat Dec  3 12:35:13 2011	(r228221)
+++ head/sys/sparc64/include/atomic.h	Sat Dec  3 13:51:57 2011	(r228222)
@@ -78,7 +78,7 @@
  * order which we use for running the kernel and all of the userland atomic
  * loads and stores behave as if the were followed by a membar with a mask
  * of #LoadLoad | #LoadStore | #StoreStore.  In order to be also sufficient
- * for use of relaxed memory ordering, the atomic_cas() in the acq variants 
+ * for use of relaxed memory ordering, the atomic_cas() in the acq variants
  * additionally would have to be followed by a membar #LoadLoad | #LoadStore.
  * Due to the suggested assembly syntax of the membar operands containing a
  * # character, they cannot be used in macros.  The cmask and mmask bits thus
@@ -97,6 +97,7 @@
 #define	atomic_cas_acq(p, e, s, sz) ({					\
 	itype(sz) v;							\
 	v = atomic_cas((p), (e), (s), sz);				\
+	__asm __volatile("" : : : "memory");				\
 	v;								\
 })
 
@@ -121,6 +122,7 @@
 #define	atomic_op_acq(p, op, v, sz) ({					\
 	itype(sz) t;							\
 	t = atomic_op((p), op, (v), sz);				\
+	__asm __volatile("" : : : "memory");				\
 	t;								\
 })
 
@@ -137,6 +139,7 @@
 #define	atomic_load_acq(p, sz) ({					\
 	itype(sz) v;							\
 	v = atomic_load((p), sz);					\
+	__asm __volatile("" : : : "memory");				\
 	v;								\
 })