Merge branch 'linus' into x86/urgent

[linux-2.6-omap-h63xx.git] / include / linux / rcupdate.h

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index d32c14de270ea28a1490c3241fe71057a1b0f582..d42dbec0608343c9471c3fd3a8c8ae734e27e55f 100644 (file)
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -33,8 +33,6 @@
 #ifndef __LINUX_RCUPDATE_H
 #define __LINUX_RCUPDATE_H
 
-#ifdef __KERNEL__
-
 #include <linux/cache.h>
 #include <linux/spinlock.h>
 #include <linux/threads.h>
@@ -133,18 +131,6 @@ struct rcu_head {
  */
 #define rcu_read_unlock_bh() __rcu_read_unlock_bh()
 
-/*
- * Prevent the compiler from merging or refetching accesses.  The compiler
- * is also forbidden from reordering successive instances of ACCESS_ONCE(),
- * but only when the compiler is aware of some particular ordering.  One way
- * to make the compiler aware of ordering is to put the two invocations of
- * ACCESS_ONCE() in different C statements.
- *
- * This macro does absolutely -nothing- to prevent the CPU from reordering,
- * merging, or refetching absolutely anything at any time.
- */
-#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
-
 /**
  * rcu_dereference - fetch an RCU-protected pointer in an
  * RCU read-side critical section.  This pointer may later
@@ -174,10 +160,13 @@ struct rcu_head {
  * code.
  */
 
-#define rcu_assign_pointer(p, v)       ({ \
-                                               smp_wmb(); \
-                                               (p) = (v); \
-                                       })
+#define rcu_assign_pointer(p, v) \
+       ({ \
+               if (!__builtin_constant_p(v) || \
+                   ((v) != NULL)) \
+                       smp_wmb(); \
+               (p) = (v); \
+       })
 
 /**
  * synchronize_sched - block until all CPUs have exited any non-preemptive
@@ -242,5 +231,4 @@ extern long rcu_batches_completed_bh(void);
 extern void rcu_init(void);
 extern int rcu_needs_cpu(int cpu);
 
-#endif /* __KERNEL__ */
 #endif /* __LINUX_RCUPDATE_H */