[PATCH tip/core/rcu 1/3] rcu: avoid build error for third-party modules

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

The initial definition of __kfree_rcu() checked a static inline function
argument to see if it was a compile-time constant.  Apparently not all
compilers are willing to put up with this at all optimization levels.
Add a nasty comment and remove the warning, relying on the fact that
__kfree_rcu() is called only from kfree_rcu(), which always passes in
a compile-time constant.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 include/linux/rcupdate.h |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 99f9aa7..58b13f1 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -814,13 +814,14 @@ static __always_inline bool __is_kfree_rcu_offset(unsigned long offset)
 	return offset < 4096;
 }
 
+/*
+ * Intended to be called only from the kfree_rcu() macro.
+ */
 static __always_inline
 void __kfree_rcu(struct rcu_head *head, unsigned long offset)
 {
 	typedef void (*rcu_callback)(struct rcu_head *);
 
-	BUILD_BUG_ON(!__builtin_constant_p(offset));
-
 	/* See the kfree_rcu() header comment. */
 	BUILD_BUG_ON(!__is_kfree_rcu_offset(offset));
 
-- 
1.7.3.2