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Date: Mon, 29 Jun 2026 15:58:33 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Breno Leitao <leitao@debian.org>
Cc: Runyu Xiao <runyu.xiao@seu.edu.cn>, davem <davem@davemloft.net>,
 edumazet <edumazet@google.com>, pabeni <pabeni@redhat.com>, horms
 <horms@kernel.org>, sashal <sashal@kernel.org>, bigeasy
 <bigeasy@linutronix.de>, netdev <netdev@vger.kernel.org>, linux-kernel
 <linux-kernel@vger.kernel.org>, "jianhao.xu" <jianhao.xu@seu.edu.cn>
Subject: Re: [RFC PATCH net-next] netpoll: hold RCU while walking napi_list
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References: <20260627101228.1191586-1-runyu.xiao@seu.edu.cn>
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On Mon, 29 Jun 2026 04:17:10 -0700 Breno Leitao wrote:
> > Sure, sorry for not including it in the RFC.  The warning was from the
> > reviewed reproducer used for the CONFIG_PROVE_RCU_LIST triage, not from
> > a production crash.  The relevant part of the dmesg is:  
> 
> Reading it, it does not come from the kernel's netpoll code at
> all -- it comes from an out-of-tree module (!?)

Yes, like Breno says, we need an in-kernel path that can trigger the
issue. Out-of-tree reproducers can be useful to validate the fix, but
they are not useful to prove that a problem actually exists.

We try to avoid defensive programming in the kernel.