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From: David Xu <davidxu@FreeBSD.org>
Date: Mon, 16 Jan 2012 06:15:14 +0000 (UTC)
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Subject: svn commit: r230201 - head/lib/libc/gen
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Author: davidxu
Date: Mon Jan 16 06:15:14 2012
New Revision: 230201
URL: http://svn.freebsd.org/changeset/base/230201

Log:
  Insert read memory barriers.

Modified:
  head/lib/libc/gen/sem.c
  head/lib/libc/gen/sem_new.c

Modified: head/lib/libc/gen/sem.c
==============================================================================
--- head/lib/libc/gen/sem.c	Mon Jan 16 06:00:44 2012	(r230200)
+++ head/lib/libc/gen/sem.c	Mon Jan 16 06:15:14 2012	(r230201)
@@ -434,7 +434,7 @@ _libc_sem_post_compat(sem_t *sem)
 		return ksem_post((*sem)->semid);
 
 	atomic_add_rel_int(&(*sem)->count, 1);
-
+	rmb();
 	if ((*sem)->nwaiters)
 		return _umtx_wake(&(*sem)->count);
 	return (0);

Modified: head/lib/libc/gen/sem_new.c
==============================================================================
--- head/lib/libc/gen/sem_new.c	Mon Jan 16 06:00:44 2012	(r230200)
+++ head/lib/libc/gen/sem_new.c	Mon Jan 16 06:15:14 2012	(r230201)
@@ -332,6 +332,7 @@ _sem_getvalue(sem_t * __restrict sem, in
 static __inline int
 usem_wake(struct _usem *sem)
 {
+	rmb();
 	if (!sem->_has_waiters)
 		return (0);
 	return _umtx_op(sem, UMTX_OP_SEM_WAKE, 0, NULL, NULL);