1 files changed, 51 insertions, 3 deletions

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index b70cc91a7831..fe46e7008667 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1928,6 +1928,33 @@ static void do_nocb_bypass_wakeup_timer(struct timer_list *t)
 	__call_rcu_nocb_wake(rdp, true, flags);
 }
 
+static inline bool nocb_gp_enabled_cb(struct rcu_data *rdp)
+{
+	u8 flags = SEGCBLIST_OFFLOADED | SEGCBLIST_KTHREAD_GP;
+
+	return rcu_segcblist_test_flags(&rdp->cblist, flags);
+}
+
+static inline bool nocb_gp_update_state(struct rcu_data *rdp, bool *needwake_state)
+{
+	struct rcu_segcblist *cblist = &rdp->cblist;
+
+	if (rcu_segcblist_test_flags(cblist, SEGCBLIST_OFFLOADED)) {
+		return true;
+	} else {
+		/*
+		 * De-offloading. Clear our flag and notify the de-offload worker.
+		 * We will ignore this rdp until it ever gets re-offloaded.
+		 */
+		WARN_ON_ONCE(!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_GP));
+		rcu_segcblist_clear_flags(cblist, SEGCBLIST_KTHREAD_GP);
+		if (!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB))
+			*needwake_state = true;
+		return false;
+	}
+}
+
+
 /*
  * No-CBs GP kthreads come here to wait for additional callbacks to show up
  * or for grace periods to end.
@@ -1956,8 +1983,17 @@ static void nocb_gp_wait(struct rcu_data *my_rdp)
 	 */
 	WARN_ON_ONCE(my_rdp->nocb_gp_rdp != my_rdp);
 	for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_cb_rdp) {
+		bool needwake_state = false;
+		if (!nocb_gp_enabled_cb(rdp))
+			continue;
 		trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("Check"));
 		rcu_nocb_lock_irqsave(rdp, flags);
+		if (!nocb_gp_update_state(rdp, &needwake_state)) {
+			rcu_nocb_unlock_irqrestore(rdp, flags);
+			if (needwake_state)
+				swake_up_one(&rdp->nocb_state_wq);
+			continue;
+		}
 		bypass_ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass);
 		if (bypass_ncbs &&
 		    (time_after(j, READ_ONCE(rdp->nocb_bypass_first) + 1) ||
@@ -2221,7 +2257,8 @@ static void do_nocb_deferred_wakeup(struct rcu_data *rdp)
 static int __rcu_nocb_rdp_deoffload(struct rcu_data *rdp)
 {
 	struct rcu_segcblist *cblist = &rdp->cblist;
-	bool wake_cb = false;
+	struct rcu_data *rdp_gp = rdp->nocb_gp_rdp;
+	bool wake_cb = false, wake_gp = false;
 	unsigned long flags;
 
 	printk("De-offloading %d\n", rdp->cpu);
@@ -2247,9 +2284,19 @@ static int __rcu_nocb_rdp_deoffload(struct rcu_data *rdp)
 	if (wake_cb)
 		swake_up_one(&rdp->nocb_cb_wq);
 
-	swait_event_exclusive(rdp->nocb_state_wq,
-			      !rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB));
+	raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags);
+	if (rdp_gp->nocb_gp_sleep) {
+		rdp_gp->nocb_gp_sleep = false;
+		wake_gp = true;
+	}
+	raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);
 
+	if (wake_gp)
+		wake_up_process(rdp_gp->nocb_gp_kthread);
+
+	swait_event_exclusive(rdp->nocb_state_wq,
+			      !rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB |
+							SEGCBLIST_KTHREAD_GP));
 	return 0;
 }
 
@@ -2332,6 +2379,7 @@ void __init rcu_init_nohz(void)
 			rcu_segcblist_init(&rdp->cblist);
 		rcu_segcblist_offload(&rdp->cblist, true);
 		rcu_segcblist_set_flags(&rdp->cblist, SEGCBLIST_KTHREAD_CB);
+		rcu_segcblist_set_flags(&rdp->cblist, SEGCBLIST_KTHREAD_GP);
 	}
 	rcu_organize_nocb_kthreads();
 }