netdev - Re: [PATCH net-next v3] page_pool: avoid infinite loop to schedule delayed worker

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Message-ID: <165410d2-98b5-48d2-9e51-6590d014bfd6@kernel.org>
Date: Mon, 17 Feb 2025 10:38:48 +0100
From: Jesper Dangaard Brouer <hawk@...nel.org>
To: Jason Xing <kerneljasonxing@...il.com>,
 Mina Almasry <almasrymina@...gle.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
 pabeni@...hat.com, horms@...nel.org, ilias.apalodimas@...aro.org,
 netdev@...r.kernel.org
Subject: Re: [PATCH net-next v3] page_pool: avoid infinite loop to schedule
 delayed worker



On 15/02/2025 00.14, Jason Xing wrote:
> On Sat, Feb 15, 2025 at 4:27 AM Mina Almasry <almasrymina@...gle.com> wrote:
>>
>> On Thu, Feb 13, 2025 at 10:43 PM Jason Xing <kerneljasonxing@...il.com> wrote:
>>>
>>> We noticed the kworker in page_pool_release_retry() was waken
>>> up repeatedly and infinitely in production because of the
>>> buggy driver causing the inflight less than 0 and warning
>>> us in page_pool_inflight()[1].
>>>
>>> Since the inflight value goes negative, it means we should
>>> not expect the whole page_pool to get back to work normally.
>>>
>>> This patch mitigates the adverse effect by not rescheduling
>>> the kworker when detecting the inflight negative in
>>> page_pool_release_retry().
>>>
>>> [1]
>>> [Mon Feb 10 20:36:11 2025] ------------[ cut here ]------------
>>> [Mon Feb 10 20:36:11 2025] Negative(-51446) inflight packet-pages
>>> ...
>>> [Mon Feb 10 20:36:11 2025] Call Trace:
>>> [Mon Feb 10 20:36:11 2025]  page_pool_release_retry+0x23/0x70
>>> [Mon Feb 10 20:36:11 2025]  process_one_work+0x1b1/0x370
>>> [Mon Feb 10 20:36:11 2025]  worker_thread+0x37/0x3a0
>>> [Mon Feb 10 20:36:11 2025]  kthread+0x11a/0x140
>>> [Mon Feb 10 20:36:11 2025]  ? process_one_work+0x370/0x370
>>> [Mon Feb 10 20:36:11 2025]  ? __kthread_cancel_work+0x40/0x40
>>> [Mon Feb 10 20:36:11 2025]  ret_from_fork+0x35/0x40
>>> [Mon Feb 10 20:36:11 2025] ---[ end trace ebffe800f33e7e34 ]---
>>> Note: before this patch, the above calltrace would flood the
>>> dmesg due to repeated reschedule of release_dw kworker.
>>>
>>> Signed-off-by: Jason Xing <kerneljasonxing@...il.com>
>>
>> Thanks Jason,
>>
>> Reviewed-by: Mina Almasry <almasrymina@...gle.com>
> 
> Thanks for the review.
> 
>>
>> When you find the root cause of the driver bug, if you can think of
>> ways to catch it sooner in the page_pool or prevent drivers from
>> triggering it, please do consider sending improvements upstream.
>> Thanks!
> 
> Sure, it's exactly what I want to do :)

What driver is this happening in?

--Jesper