rcu: add tracing for RCU's kthread run states.

Add tracing to help debugging situations when RCU's kthreads are not
running but are supposed to be.

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

1 files changed, 11 insertions, 0 deletions

diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index d49046c79c59..67341dbebd95 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -89,6 +89,13 @@ struct rcu_dynticks {
         atomic_t dynticks;      /* Even value for dynticks-idle, else odd. */
 };
 
+/* RCU's kthread states for tracing. */
+#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
+
 /*
  * Definition for node within the RCU grace-period-detection hierarchy.
  */
@@ -152,6 +159,8 @@ struct rcu_node {
         wait_queue_head_t boost_wq;
                                 /* Wait queue on which to park the boost */
                                 /*  kthread. */
+        unsigned int boost_kthread_status;
+                                /* State of boost_kthread_task for tracing. */
         unsigned long n_tasks_boosted;
                                 /* Total number of tasks boosted. */
         unsigned long n_exp_boosts;
@@ -179,6 +188,8 @@ struct rcu_node {
         wait_queue_head_t node_wq;
                                 /* Wait queue on which to park the per-node */
                                 /*  kthread. */
+        unsigned int node_kthread_status;
+                                /* State of node_kthread_task for tracing. */
 } ____cacheline_internodealigned_in_smp;
 
 /*