linux-kernel - Re: [PATCH 6.6 3/3] net: Allow to use SMP threads for backlog NAPI.

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Message-ID: <2a4cfb05-f627-4f07-a0a3-a5c05d91bac3@linux.dev>
Date: Sun, 8 Feb 2026 04:26:48 +0800
From: Wen Yang <wen.yang@...ux.dev>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: Jakub Kicinski <kuba@...nel.org>, stable@...r.kernel.org,
 linux-kernel@...r.kernel.org, Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH 6.6 3/3] net: Allow to use SMP threads for backlog NAPI.

On 2/4/26 21:54, Greg Kroah-Hartman wrote:
> On Tue, Jan 20, 2026 at 11:38:33AM +0100, Sebastian Andrzej Siewior wrote:
>> On 2026-01-20 10:21:58 [+0100], Greg Kroah-Hartman wrote:
>>>>> Please see patch 0/3 in this series:
>>>>> 	https://lore.kernel.org/all/cover.1768751557.git.wen.yang@linux.dev/
>>>>
>>>> The reasoning why this is needed is due to PREEMPT_RT. This targets v6.6
>>>> and PREEMPT_RT is officially supported upstream since v6.12. For v6.6
>>>> you still need the out-of-tree patch. This means not only select the
>>>> Kconfig symbol but also a bit futex, ptrace or printk. This queue does
>>>> not include the three patches here but has another workaround having
>>>> more or less the same effect.
>>>>
>>>> If this is needed only for PREEMPT_RT's sake I would suggest to route it
>>>> via the stable-rt instead and replace what is currently there.
>>>
>>> It's already merged, should this be reverted?  I forgot RT was only for
>>> 6.12 and newer, sorry.
>>
>> Jakub doesn't seem to be thrilled about this backport and I don't see a
>> requirement for it. Based on this yes, please revert it.
>>
>> If Wen wants this still to happen he should either provide better
>> reasoning why this is needed based on the latest stable v6.6 as-is or
>> ask stable-rt team to take this instead the current workaround.
> 
> Ok, both now reverted, thanks for the review!
> 

Thank you, we are using 6.6/6.1 lts + rt patch, and this issue 
occasionally occurs in production environments.

Based on the above comments, we are also trying further back porting and 
testing, which involves many changes and may take some time.

After it has been fully tested, we will send it out for review again.

--
Best wishes,
Wen