Re: [PATCH net v3 2/2] net: ethernet: oa_tc6: fix tx skb race condition between reference pointers

[<Parthiban.Veerasooran@microchip.com>]

Hi Jakub,

On 14/12/24 8:12 am, Jakub Kicinski wrote:
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> 
> On Fri, 13 Dec 2024 10:35:03 +0000 Parthiban.Veerasooran@microchip.com
> wrote:
>>>> start_xmit runs in BH / softirq context. You can't take sleeping locks.
>>>> The lock has to be a spin lock. You could possibly try to use the
>>>> existing spin lock of the tx queue (__netif_tx_lock()) but that may be
>>>> more challenging to do cleanly from within a library..
>>> Thanks for the input. Yes, it looks like implementing a spin lock would
>>> be a right choice. I will implement it and do the testing as you
>>> suggested below and share the feedback.
>> I tried using spin_lock_bh() variants (as the softirq involved) on both
>> start_xmit() and spi_thread() where the critical regions need to be
>> protected and tested by enabling the Kconfigs in the
>> kernel/configs/debug.config. Didn't notice any warnings in the dmesg log.
>>
>> Note: Prior to the above test, purposefully I tried with spin_lock()
>> variants on both the sides to check/simulate for the warnings using
>> Kconfigs kernel/configs/debug.config. Got some warnings in the dmesg
>> regarding deadlock which clarified the expected behavior. And then I
>> proceeded with the above fix and it worked as expected.
>>
>> If you agree, I will prepare the next version with this fix and post.
> 
> Go ahead.
Thanks for your comment. It is already posted for review.

https://patchwork.kernel.org/project/netdevbpf/patch/20241213123159.439739-3-parthiban.veerasooran@microchip.com/

Best regards,
Parthiban V