netdev - [PATCH net] netdevsim: disable local BH when scheduling NAPI

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Message-Id: <20250212-netdevsim-v1-1-20ece94daae8@debian.org>
Date: Wed, 12 Feb 2025 10:34:22 -0800
From: Breno Leitao <leitao@...ian.org>
To: Jakub Kicinski <kuba@...nel.org>, Andrew Lunn <andrew+netdev@...n.ch>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Paolo Abeni <pabeni@...hat.com>, David Wei <dw@...idwei.uk>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 paulmck@...nel.org, kernel-team@...a.com, stable@...r.kernel.org, 
 Breno Leitao <leitao@...ian.org>
Subject: [PATCH net] netdevsim: disable local BH when scheduling NAPI

The netdevsim driver was getting NOHZ tick-stop errors during packet
transmission due to pending softirq work when calling napi_schedule().

This is showing the following message when running netconsole selftest.

	NOHZ tick-stop error: local softirq work is pending, handler #08!!!

Add local_bh_disable()/enable() around the napi_schedule() call to
prevent softirqs from being handled during this xmit.

Cc: stable@...r.kernel.org
Fixes: 3762ec05a9fb ("netdevsim: add NAPI support")
Suggested-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Breno Leitao <leitao@...ian.org>
---
 drivers/net/netdevsim/netdev.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c
index 42f247cbdceecbadf27f7090c030aa5bd240c18a..6aeb081b06da226ab91c49f53d08f465570877ae 100644
--- a/drivers/net/netdevsim/netdev.c
+++ b/drivers/net/netdevsim/netdev.c
@@ -87,7 +87,9 @@ static netdev_tx_t nsim_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	if (unlikely(nsim_forward_skb(peer_dev, skb, rq) == NET_RX_DROP))
 		goto out_drop_cnt;

+	local_bh_disable();
 	napi_schedule(&rq->napi);
+	local_bh_enable();

 	rcu_read_unlock();
 	u64_stats_update_begin(&ns->syncp);

---
base-commit: cf33d96f50903214226b379b3f10d1f262dae018
change-id: 20250212-netdevsim-258d2d628175

Best regards,
-- 
Breno Leitao <leitao@...ian.org>