netdev - Re: [PATCH net] net: lwtunnel: disable preemption when required

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Message-ID: <85eefdd9-ec5d-4113-8a50-5d9ea11c8bf5@uliege.be>
Date: Sun, 6 Apr 2025 10:59:45 +0200
From: Justin Iurman <justin.iurman@...ege.be>
To: Sebastian Sewior <bigeasy@...utronix.de>,
 Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Stanislav Fomichev <stfomichev@...il.com>,
 Network Development <netdev@...r.kernel.org>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Simon Horman <horms@...nel.org>, Kuniyuki Iwashima <kuniyu@...zon.com>,
 bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH net] net: lwtunnel: disable preemption when required

On 4/4/25 16:19, Sebastian Sewior wrote:
> Alexei, thank you for the Cc.
> 
> On 2025-04-03 13:35:10 [-0700], Alexei Starovoitov wrote:
>> Stating the obvious...
>> Sebastian did a lot of work removing preempt_disable from the networking
>> stack.
>> We're certainly not adding them back.
>> This patch is no go.
> 
> While looking through the code, it looks as if lwtunnel_xmit() lacks a
> local_bh_disable().

Thanks Sebastian for the confirmation, as the initial idea was to use 
local_bh_disable() as well. Then I thought preempt_disable() would be 
enough in this context, but I didn't realize you made efforts to remove 
it from the networking stack.

@Alexei, just to clarify: would you ACK this patch if we do 
s/preempt_{disable|enable}()/local_bh_{disable|enable}()/g ?

> Sebastian