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

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Date:   Thu, 2 Feb 2023 16:10:26 -0800
From:   Richard Cochran <richardcochran@...il.com>
To:     Miroslav Lichvar <mlichvar@...hat.com>
Cc:     Íñigo Huguet <ihuguet@...hat.com>,
        netdev@...r.kernel.org, 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 05:33:15PM +0100, Miroslav Lichvar wrote:
> 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.

Can ptp_vclock_gettime use a mutex instead?

Thanks,
Richard