3 files changed, 19 insertions, 28 deletions

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index aeea697d6f9f..4ea28e820f4a 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3899,11 +3899,6 @@ static void rcu_adopt_orphan_cbs(struct rcu_state *rsp, unsigned long flags)
 
 	lockdep_assert_held(&rsp->orphan_lock);
 
-	/* No-CBs CPUs are handled specially. */
-	if (!IS_ENABLED(CONFIG_HOTPLUG_CPU) ||
-	    rcu_nocb_adopt_orphan_cbs(rsp, rdp, flags))
-		return;
-
 	/* Do the accounting first. */
 	if (rsp->orphan_done.len_lazy != rsp->orphan_done.len)
 		rcu_idle_count_callbacks_posted();
@@ -3928,13 +3923,20 @@ static void rcu_adopt_orphan_cbs(struct rcu_state *rsp, unsigned long flags)
 static void rcu_migrate_callbacks(int cpu, struct rcu_state *rsp)
 {
 	unsigned long flags;
+	struct rcu_data *my_rdp;
 	struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
 	struct rcu_node *rnp = rdp->mynode;  /* Outgoing CPU's rdp & rnp. */
 
 	if (rcu_is_nocb_cpu(cpu) || rcu_segcblist_empty(&rdp->cblist))
 		return;  /* No callbacks to migrate. */
 
-	raw_spin_lock_irqsave(&rsp->orphan_lock, flags);
+	local_irq_save(flags);
+	my_rdp = this_cpu_ptr(rsp->rda);
+	if (rcu_nocb_adopt_orphan_cbs(my_rdp, rdp, flags)) {
+		local_irq_restore(flags);
+		return;
+	}
+	raw_spin_lock(&rsp->orphan_lock); /* irqs already disabled. */
 	rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp);
 	rcu_adopt_orphan_cbs(rsp, flags);
 	raw_spin_unlock_irqrestore(&rsp->orphan_lock, flags);
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index aec53c4d4aec..574513cf49b4 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -493,7 +493,7 @@ static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq);
 static void rcu_init_one_nocb(struct rcu_node *rnp);
 static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
 			    bool lazy, unsigned long flags);
-static bool rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp,
+static bool rcu_nocb_adopt_orphan_cbs(struct rcu_data *my_rdp,
 				      struct rcu_data *rdp,
 				      unsigned long flags);
 static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp);
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 908b309d60d7..ff7d5ee49816 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1961,30 +1961,19 @@ static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
  * Adopt orphaned callbacks on a no-CBs CPU, or return 0 if this is
  * not a no-CBs CPU.
  */
-static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp,
+static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_data *my_rdp,
 						     struct rcu_data *rdp,
 						     unsigned long flags)
 {
-	long ql = rsp->orphan_done.len;
-	long qll = rsp->orphan_done.len_lazy;
-
-	/* If this is not a no-CBs CPU, tell the caller to do it the old way. */
+	RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_nocb_adopt_orphan_cbs() invoked with irqs enabled!!!");
 	if (!rcu_is_nocb_cpu(smp_processor_id()))
-		return false;
-
-	/* First, enqueue the donelist, if any.  This preserves CB ordering. */
-	if (rsp->orphan_done.head) {
-		__call_rcu_nocb_enqueue(rdp, rcu_cblist_head(&rsp->orphan_done),
-					rcu_cblist_tail(&rsp->orphan_done),
-					ql, qll, flags);
-	}
-	if (rsp->orphan_pend.head) {
-		__call_rcu_nocb_enqueue(rdp, rcu_cblist_head(&rsp->orphan_pend),
-					rcu_cblist_tail(&rsp->orphan_pend),
-					ql, qll, flags);
-	}
-	rcu_cblist_init(&rsp->orphan_done);
-	rcu_cblist_init(&rsp->orphan_pend);
+		return false; /* Not NOCBs CPU, caller must migrate CBs. */
+	__call_rcu_nocb_enqueue(my_rdp, rcu_segcblist_head(&rdp->cblist),
+				rcu_segcblist_tail(&rdp->cblist),
+				rcu_segcblist_n_cbs(&rdp->cblist),
+				rcu_segcblist_n_lazy_cbs(&rdp->cblist), flags);
+	rcu_segcblist_init(&rdp->cblist);
+	rcu_segcblist_disable(&rdp->cblist);
 	return true;
 }
 
@@ -2459,7 +2448,7 @@ static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
 	return false;
 }
 
-static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp,
+static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_data *my_rdp,
 						     struct rcu_data *rdp,
 						     unsigned long flags)
 {