releases/5.10.20/rcu-pull-deferred-rcuog-wake-up-to-rcu_eqs_enter-callers.patch

From 54b7429efffc99e845ba9381bee3244f012a06c2 Mon Sep 17 00:00:00 2001
From: Frederic Weisbecker <frederic@kernel.org>
Date: Mon, 1 Feb 2021 00:05:44 +0100
Subject: rcu: Pull deferred rcuog wake up to rcu_eqs_enter() callers

From: Frederic Weisbecker <frederic@kernel.org>

commit 54b7429efffc99e845ba9381bee3244f012a06c2 upstream.

Deferred wakeup of rcuog kthreads upon RCU idle mode entry is going to
be handled differently whether initiated by idle, user or guest. Prepare
with pulling that control up to rcu_eqs_enter() callers.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20210131230548.32970-2-frederic@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 kernel/rcu/tree.c |   11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -636,7 +636,6 @@ static noinstr void rcu_eqs_enter(bool u
 	trace_rcu_dyntick(TPS("Start"), rdp->dynticks_nesting, 0, atomic_read(&rdp->dynticks));
 	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
 	rdp = this_cpu_ptr(&rcu_data);
-	do_nocb_deferred_wakeup(rdp);
 	rcu_prepare_for_idle();
 	rcu_preempt_deferred_qs(current);
 
@@ -664,7 +663,10 @@ static noinstr void rcu_eqs_enter(bool u
  */
 void rcu_idle_enter(void)
 {
+	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
+
 	lockdep_assert_irqs_disabled();
+	do_nocb_deferred_wakeup(rdp);
 	rcu_eqs_enter(false);
 }
 EXPORT_SYMBOL_GPL(rcu_idle_enter);
@@ -683,7 +685,14 @@ EXPORT_SYMBOL_GPL(rcu_idle_enter);
  */
 noinstr void rcu_user_enter(void)
 {
+	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
+
 	lockdep_assert_irqs_disabled();
+
+	instrumentation_begin();
+	do_nocb_deferred_wakeup(rdp);
+	instrumentation_end();
+
 	rcu_eqs_enter(true);
 }
 #endif /* CONFIG_NO_HZ_FULL */