From: Jakub Kicinski <kuba@kernel.org>
To: Dao Zhong Ma <cz1346219@gmail.com>
Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
antonio@openvpn.net, sd@queasysnail.net, andrew+netdev@lunn.ch,
davem@davemloft.net, edumazet@google.com, pabeni@redhat.com
Subject: Re: [PATCH 1/1] ovpn: tcp - defer TX from softirq to workqueue
Date: Fri, 1 May 2026 16:12:26 -0700 [thread overview]
Message-ID: <20260501161226.0239262c@kernel.org> (raw)
In-Reply-To: <20260501145425.757147-2-cz1346219@gmail.com>
On Fri, 1 May 2026 22:54:25 +0800 Dao Zhong Ma wrote:
> ovpn_tcp_send_skb() holds sk->sk_lock.slock while performing the full TCP
> send in softirq context. This can hold the spinlock for a long time
> (large skb), blocking lock_sock() users. This can starve the RCU GP
> kthread and trigger RCU stalls warnings and hung tasks.
>
> Defer the TCP send operation to process context:
> - In interrupt context, only enqueue the skb under the spinlock
> schedule tcp_tx_work.
> - In process context, dequeue and flush the send queue under lock_sock()
>
> This reduces the softirq critical section to a short duration, allowing
> lock_sock() users to make progress and preventing RCU stalls.
This appears to break the ovpn selftests
next prev parent reply other threads:[~2026-05-01 23:12 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-01 14:54 [PATCH 0/1] ovpn: tcp - defer TX from softirq to workqueue Dao Zhong Ma
2026-05-01 14:54 ` [PATCH 1/1] " Dao Zhong Ma
2026-05-01 23:12 ` Jakub Kicinski [this message]
2026-05-03 21:14 ` Antonio Quartulli
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