diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 90c8be22d57a..f51385b86ea3 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -418,16 +418,23 @@ void rcu_momentary_dyntick_idle(void)
 EXPORT_SYMBOL_GPL(rcu_momentary_dyntick_idle);
 
 /**
- * rcu_is_cpu_rrupt_from_idle - see if interrupted from idle
+ * rcu_is_cpu_rrupt_from_idle - see if 'interrupted' from idle
  *
  * If the current CPU is idle and running at a first-level (not nested)
- * interrupt from idle, return true.  The caller must have at least
- * disabled preemption.
+ * interrupt, or directly, from idle, return true.
+ *
+ * The caller must have at least disabled IRQs.
  */
 static int rcu_is_cpu_rrupt_from_idle(void)
 {
-	/* Called only from within the scheduling-clock interrupt */
-	lockdep_assert_in_irq();
+	long nesting;
+
+	/*
+	 * Usually called from the tick; but also used from smp_function_call()
+	 * for expedited grace periods. This latter can result in running from
+	 * the idle task, instead of an actual IPI.
+	 */
+	lockdep_assert_irqs_disabled();
 
 	/* Check for counter underflows */
 	RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nesting) < 0,
@@ -436,9 +443,15 @@ static int rcu_is_cpu_rrupt_from_idle(void)
 			 "RCU dynticks_nmi_nesting counter underflow/zero!");
 
 	/* Are we at first interrupt nesting level? */
-	if (__this_cpu_read(rcu_data.dynticks_nmi_nesting) != 1)
+	nesting = __this_cpu_read(rcu_data.dynticks_nmi_nesting);
+	if (nesting > 1)
 		return false;
 
+	/*
+	 * If we're not in an interrupt, we must be in the idle task!
+	 */
+	WARN_ON_ONCE(!nesting && !is_idle_task(current));
+
 	/* Does CPU appear to be idle from an RCU standpoint? */
 	return __this_cpu_read(rcu_data.dynticks_nesting) == 0;
 }