linux-kernel - [PATCH 1/3] rcu/nocb: Extract nocb_defer_wakeup

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Message-Id: <20260103221117.521087-2-joelagnelf@nvidia.com>
Date: Sat,  3 Jan 2026 17:11:15 -0500
From: Joel Fernandes <joelagnelf@...dia.com>
To: linux-kernel@...r.kernel.org
Cc: "Paul E . McKenney" <paulmck@...nel.org>,
	Boqun Feng <boqun.feng@...il.com>,
	rcu@...r.kernel.org,
	Frederic Weisbecker <frederic@...nel.org>,
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
	Josh Triplett <josh@...htriplett.org>,
	Uladzislau Rezki <urezki@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Zqiang <qiang.zhang@...ux.dev>,
	Joel Fernandes <joelagnelf@...dia.com>
Subject: [PATCH 1/3] rcu/nocb: Extract nocb_defer_wakeup_cancel() helper

The pattern of checking nocb_defer_wakeup and deleting the timer is
duplicated in __wake_nocb_gp() and nocb_gp_wait(). Extract this into a
common helper function nocb_defer_wakeup_cancel().

This removes code duplication and makes it easier to maintain.

Signed-off-by: Joel Fernandes <joelagnelf@...dia.com>
---
 kernel/rcu/tree_nocb.h | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
index d3e6a0e77210..d9687317a2a3 100644
--- a/kernel/rcu/tree_nocb.h
+++ b/kernel/rcu/tree_nocb.h
@@ -190,6 +190,15 @@ static void rcu_init_one_nocb(struct rcu_node *rnp)
 	init_swait_queue_head(&rnp->nocb_gp_wq[1]);
 }
 
+/* Clear any pending deferred wakeup timer (nocb_gp_lock must be held). */
+static void nocb_defer_wakeup_cancel(struct rcu_data *rdp_gp)
+{
+	if (rdp_gp->nocb_defer_wakeup > RCU_NOCB_WAKE_NOT) {
+		WRITE_ONCE(rdp_gp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT);
+		timer_delete(&rdp_gp->nocb_timer);
+	}
+}
+
 static bool __wake_nocb_gp(struct rcu_data *rdp_gp,
 			   struct rcu_data *rdp,
 			   bool force, unsigned long flags)
@@ -204,10 +213,7 @@ static bool __wake_nocb_gp(struct rcu_data *rdp_gp,
 		return false;
 	}
 
-	if (rdp_gp->nocb_defer_wakeup > RCU_NOCB_WAKE_NOT) {
-		WRITE_ONCE(rdp_gp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT);
-		timer_delete(&rdp_gp->nocb_timer);
-	}
+	nocb_defer_wakeup_cancel(rdp_gp);
 
 	if (force || READ_ONCE(rdp_gp->nocb_gp_sleep)) {
 		WRITE_ONCE(rdp_gp->nocb_gp_sleep, false);
@@ -815,10 +821,7 @@ static void nocb_gp_wait(struct rcu_data *my_rdp)
 		if (rdp_toggling)
 			my_rdp->nocb_toggling_rdp = NULL;
 
-		if (my_rdp->nocb_defer_wakeup > RCU_NOCB_WAKE_NOT) {
-			WRITE_ONCE(my_rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT);
-			timer_delete(&my_rdp->nocb_timer);
-		}
+		nocb_defer_wakeup_cancel(my_rdp);
 		WRITE_ONCE(my_rdp->nocb_gp_sleep, true);
 		raw_spin_unlock_irqrestore(&my_rdp->nocb_gp_lock, flags);
 	} else {
-- 
2.34.1