rcu: Change _wait_rcu_gp() to work around GCC bug 67055

Code like this in inline functions confuses some recent versions of gcc:

	const int n = const-expr;
	whatever_t array[n];

For more details, see:

	https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67055#c13

This compiler bug results in the following failure after 114b7fd4b (rcu:
Create rcu_sync infrastructure):

	In file included from include/linux/rcupdate.h:429:0,
			  from include/linux/rcu_sync.h:5,
			  from kernel/rcu/sync.c:1:
	include/linux/rcutiny.h: In function 'rcu_barrier_sched':
	include/linux/rcutiny.h:55:20: internal compiler error: Segmentation fault
	  static inline void rcu_barrier_sched(void)

This commit therefore eliminates the constant local variable in favor of
direct use of the expression.

Reported-and-tested-by: Mark Salter <msalter@redhat.com>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index ff476515f7163ab1b0247cfd64c0a4f6a364b2f3..581abf84856691ad2e5ce39f77f9c9112170061c 100644 (file)
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -230,12 +230,11 @@ void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array,
                   struct rcu_synchronize *rs_array);
 
 #define _wait_rcu_gp(checktiny, ...) \
-do { \
-       call_rcu_func_t __crcu_array[] = { __VA_ARGS__ }; \
-       const int __n = ARRAY_SIZE(__crcu_array); \
-       struct rcu_synchronize __rs_array[__n]; \
-       \
-       __wait_rcu_gp(checktiny, __n, __crcu_array, __rs_array); \
+do {                                                                   \
+       call_rcu_func_t __crcu_array[] = { __VA_ARGS__ };               \
+       struct rcu_synchronize __rs_array[ARRAY_SIZE(__crcu_array)];    \
+       __wait_rcu_gp(checktiny, ARRAY_SIZE(__crcu_array),              \
+                       __crcu_array, __rs_array);                      \
 } while (0)
 
 #define wait_rcu_gp(...) _wait_rcu_gp(false, __VA_ARGS__)