rcu: Prepare for synchronization fixes: clean up for non-NO_HZ handling of ->completed counter

Impose a clear locking design on non-NO_HZ handling of the
->completed counter.  This increases the distance between the
RCU and the CPU-hotplug mechanisms.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
Cc: <stable@kernel.org> # .32.x
LKML-Reference: <12571987491353-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 4 insertions, 4 deletions

diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 1899023b0962..8a4c1650ad8d 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -204,11 +204,12 @@ struct rcu_data {
 #define RCU_GP_IDLE             0       /* No grace period in progress. */
 #define RCU_GP_INIT             1       /* Grace period being initialized. */
 #define RCU_SAVE_DYNTICK        2       /* Need to scan dyntick state. */
-#define RCU_FORCE_QS            3       /* Need to force quiescent state. */
+#define RCU_SAVE_COMPLETED      3       /* Need to save rsp->completed. */
+#define RCU_FORCE_QS            4       /* Need to force quiescent state. */
 #ifdef CONFIG_NO_HZ
 #define RCU_SIGNAL_INIT         RCU_SAVE_DYNTICK
 #else /* #ifdef CONFIG_NO_HZ */
-#define RCU_SIGNAL_INIT         RCU_FORCE_QS
+#define RCU_SIGNAL_INIT         RCU_SAVE_COMPLETED
 #endif /* #else #ifdef CONFIG_NO_HZ */
 
 #define RCU_JIFFIES_TILL_FORCE_QS        3      /* for rsp->jiffies_force_qs */
@@ -274,9 +275,8 @@ struct rcu_state {
         unsigned long jiffies_stall;            /* Time at which to check */
                                                 /*  for CPU stalls. */
 #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
-#ifdef CONFIG_NO_HZ
         long dynticks_completed;                /* Value of completed @ snap. */
-#endif /* #ifdef CONFIG_NO_HZ */
+                                                /*  Protected by fqslock. */
 };
 
 #ifdef RCU_TREE_NONCORE