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, 3 insertions, 0 deletions

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 07d346445d12..22a6a46de7c6 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -1198,11 +1198,13 @@ static int rcu_boost_kthread(void *arg)
         int more2boost;
 
         for (;;) {
+                rnp->boost_kthread_status = RCU_KTHREAD_WAITING;
                 wait_event_interruptible(rnp->boost_wq, rnp->boost_tasks ||
                                                         rnp->exp_tasks ||
                                                         kthread_should_stop());
                 if (kthread_should_stop())
                         break;
+                rnp->boost_kthread_status = RCU_KTHREAD_RUNNING;
                 more2boost = rcu_boost(rnp);
                 if (more2boost)
                         spincnt++;
@@ -1213,6 +1215,7 @@ static int rcu_boost_kthread(void *arg)
                         spincnt = 0;
                 }
         }
+        rnp->boost_kthread_status = RCU_KTHREAD_STOPPED;
         return 0;
 }