rcu: add grace-period age and more kthread state to tracing

This commit adds the age in jiffies of the current grace period along
with the duration in jiffies of the longest grace period since boot
to the rcu/rcugp debugfs file.  It also adds an additional "O" state
to kthread tracing to differentiate between the kthread waiting due to
having nothing to do on the one hand and waiting due to being on the
wrong CPU on the other hand.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 67341dbebd95..37502a27a072 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -93,8 +93,9 @@ struct rcu_dynticks {
 #define RCU_KTHREAD_STOPPED  0
 #define RCU_KTHREAD_RUNNING  1
 #define RCU_KTHREAD_WAITING  2
-#define RCU_KTHREAD_YIELDING 3
-#define RCU_KTHREAD_MAX      3
+#define RCU_KTHREAD_OFFCPU   3
+#define RCU_KTHREAD_YIELDING 4
+#define RCU_KTHREAD_MAX      4
 
 /*
  * Definition for node within the RCU grace-period-detection hierarchy.
@@ -383,6 +384,8 @@ struct rcu_state {
                                                 /*  but in jiffies. */
         unsigned long jiffies_stall;            /* Time at which to check */
                                                 /*  for CPU stalls. */
+        unsigned long gp_max;                   /* Maximum GP duration in */
+                                                /*  jiffies. */
         char *name;                             /* Name of structure. */
 };