linux-kernel - [PATCH] wireguard/queueing: simplify wg_cpumask_next

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Message-ID: <20250604233656.41896-1-yury.norov@gmail.com>
Date: Wed,  4 Jun 2025 19:36:55 -0400
From: Yury Norov <yury.norov@...il.com>
To: "Jason A. Donenfeld" <Jason@...c4.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	wireguard@...ts.zx2c4.com,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Yury Norov <yury.norov@...il.com>
Subject: [PATCH] wireguard/queueing: simplify wg_cpumask_next_online()

wg_cpumask_choose_online() opencodes cpumask_nth(). Use it and make the
function significantly simpler. While there, fix opencoded cpu_online()
too. 

Signed-off-by: Yury Norov <yury.norov@...il.com>
---
 drivers/net/wireguard/queueing.h | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/drivers/net/wireguard/queueing.h b/drivers/net/wireguard/queueing.h
index 7eb76724b3ed..3bfe16f71af0 100644
--- a/drivers/net/wireguard/queueing.h
+++ b/drivers/net/wireguard/queueing.h
@@ -104,17 +104,11 @@ static inline void wg_reset_packet(struct sk_buff *skb, bool encapsulating)
 
 static inline int wg_cpumask_choose_online(int *stored_cpu, unsigned int id)
 {
-	unsigned int cpu = *stored_cpu, cpu_index, i;
+	if (likely(*stored_cpu < nr_cpu_ids && cpu_online(*stored_cpu)))
+		return cpu;
 
-	if (unlikely(cpu >= nr_cpu_ids ||
-		     !cpumask_test_cpu(cpu, cpu_online_mask))) {
-		cpu_index = id % cpumask_weight(cpu_online_mask);
-		cpu = cpumask_first(cpu_online_mask);
-		for (i = 0; i < cpu_index; ++i)
-			cpu = cpumask_next(cpu, cpu_online_mask);
-		*stored_cpu = cpu;
-	}
-	return cpu;
+	*stored_cpu = cpumask_nth(id % num_online_cpus(), cpu_online_mask);
+	return *stored_cpu;
 }
 
 /* This function is racy, in the sense that it's called while last_cpu is
-- 
2.43.0