netdev - Re: PTP vclock: BUG: scheduling while atomic

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Date:   Thu, 2 Feb 2023 17:33:15 +0100
From:   Miroslav Lichvar <mlichvar@...hat.com>
To:     Íñigo Huguet <ihuguet@...hat.com>
Cc:     netdev@...r.kernel.org, richardcochran@...il.com,
        yangbo.lu@....com, gerhard@...leder-embedded.com,
        habetsm.xilinx@...il.com, ecree.xilinx@...il.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, alex.maftei@....com,
        Jacob Keller <jacob.e.keller@...el.com>
Subject: Re: PTP vclock: BUG: scheduling while atomic

On Thu, Feb 02, 2023 at 05:02:07PM +0100, Íñigo Huguet wrote:
> Our QA team was testing PTP vclocks, and they've found this error with sfc NIC/driver:
>   BUG: scheduling while atomic: ptp5/25223/0x00000002
> 
> The reason seems to be that vclocks disable interrupts with `spin_lock_irqsave` in
> `ptp_vclock_gettime`, and then read the timecounter, which in turns ends calling to
> the driver's `gettime64` callback.

The same issue was observed with the ice driver:
https://lists.osuosl.org/pipermail/intel-wired-lan/Week-of-Mon-20221107/030633.html

I tried to fix it generally in the vclock support, but was not
successful. There was a hint it would be fixed in the driver. I'm not
sure what is the best approach here.

-- 
Miroslav Lichvar