rcu/nocb: Use separate flag to indicate disabled ->cblist

NULLing the RCU_NEXT_TAIL pointer was a clever way to save a byte, but
forward-progress considerations would require that this pointer be both
NULL and non-NULL, which, absent a quantum-computer port of the Linux
kernel, simply won't happen.  This commit therefore creates as separate
->enabled flag to replace the current NULL checks.

[ paulmck: Add include files per 0day test robot and -next. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/rcu_segcblist.h b/include/linux/rcu_segcblist.h
index 87404cb015f1..ed2cfd3c0743 100644
--- a/include/linux/rcu_segcblist.h
+++ b/include/linux/rcu_segcblist.h
@@ -14,6 +14,9 @@
 #ifndef __INCLUDE_LINUX_RCU_SEGCBLIST_H
 #define __INCLUDE_LINUX_RCU_SEGCBLIST_H
 
+#include <linux/types.h>
+#include <linux/atomic.h>
+
 /* Simple unsegmented callback lists. */
 struct rcu_cblist {
 	struct rcu_head *head;
@@ -67,6 +70,7 @@ struct rcu_segcblist {
 	unsigned long gp_seq[RCU_CBLIST_NSEGS];
 	long len;
 	long len_lazy;
+	u8 enabled;
 };
 
 #define RCU_SEGCBLIST_INITIALIZER(n) \