3 files changed, 29 insertions, 0 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 5b8ad827fd86..f5ab50235cba 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -794,6 +794,16 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
 		rdp->offline_fqs++;
 		return 1;
 	}
+
+	/*
+	 * There is a possibility that a CPU in adaptive-ticks state
+	 * might run in the kernel with the scheduling-clock tick disabled
+	 * for an extended time period.  Invoke rcu_kick_nohz_cpu() to
+	 * force the CPU to restart the scheduling-clock tick in this
+	 * CPU is in this state.
+	 */
+	rcu_kick_nohz_cpu(rdp->cpu);
+
 	return 0;
 }
 
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index c896b5045d9d..f993c0ac47db 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -539,6 +539,7 @@ static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
 static void rcu_spawn_nocb_kthreads(struct rcu_state *rsp);
 static void init_nocb_callback_list(struct rcu_data *rdp);
 static void __init rcu_init_nocb(void);
+static void rcu_kick_nohz_cpu(int cpu);
 
 #endif /* #ifndef RCU_TREE_NONCORE */
 
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index c1cc7e17ff9d..a5745e9b5d5a 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -28,6 +28,7 @@
 #include <linux/gfp.h>
 #include <linux/oom.h>
 #include <linux/smpboot.h>
+#include <linux/tick.h>
 
 #define RCU_KTHREAD_PRIO 1
 
@@ -2502,3 +2503,20 @@ static void __init rcu_init_nocb(void)
 }
 
 #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
+
+/*
+ * An adaptive-ticks CPU can potentially execute in kernel mode for an
+ * arbitrarily long period of time with the scheduling-clock tick turned
+ * off.  RCU will be paying attention to this CPU because it is in the
+ * kernel, but the CPU cannot be guaranteed to be executing the RCU state
+ * machine because the scheduling-clock tick has been disabled.  Therefore,
+ * if an adaptive-ticks CPU is failing to respond to the current grace
+ * period and has not be idle from an RCU perspective, kick it.
+ */
+static void rcu_kick_nohz_cpu(int cpu)
+{
+#ifdef CONFIG_NO_HZ_FULL
+	if (tick_nohz_full_cpu(cpu))
+		smp_send_reschedule(cpu);
+#endif /* #ifdef CONFIG_NO_HZ_FULL */
+}