netdev - Re: [PATCH net-next 1/5] ptp: unregister virtual clocks when unregistering physical clock.

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Message-ID: <87czkcn33p.fsf@intel.com>
Date:   Thu, 27 Jan 2022 15:58:02 -0800
From:   Vinicius Costa Gomes <vinicius.gomes@...el.com>
To:     Miroslav Lichvar <mlichvar@...hat.com>, netdev@...r.kernel.org
Cc:     Miroslav Lichvar <mlichvar@...hat.com>,
        Yangbo Lu <yangbo.lu@....com>,
        Yang Yingliang <yangyingliang@...wei.com>,
        Richard Cochran <richardcochran@...il.com>
Subject: Re: [PATCH net-next 1/5] ptp: unregister virtual clocks when
 unregistering physical clock.

Miroslav Lichvar <mlichvar@...hat.com> writes:

> When unregistering a physical clock which has some virtual clocks,
> unregister the virtual clocks with it.
>
> This fixes the following oops, which can be triggered by unloading
> a driver providing a PTP clock when it has enabled virtual clocks:
>
> BUG: unable to handle page fault for address: ffffffffc04fc4d8
> Oops: 0000 [#1] PREEMPT SMP NOPTI
> RIP: 0010:ptp_vclock_read+0x31/0xb0
> Call Trace:
>  timecounter_read+0xf/0x50
>  ptp_vclock_refresh+0x2c/0x50
>  ? ptp_clock_release+0x40/0x40
>  ptp_aux_kworker+0x17/0x30
>  kthread_worker_fn+0x9b/0x240
>  ? kthread_should_park+0x30/0x30
>  kthread+0xe2/0x110
>  ? kthread_complete_and_exit+0x20/0x20
>  ret_from_fork+0x22/0x30
>
> Fixes: 73f37068d540 ("ptp: support ptp physical/virtual clocks conversion")
> Signed-off-by: Miroslav Lichvar <mlichvar@...hat.com>
> Cc: Yangbo Lu <yangbo.lu@....com>
> Cc: Yang Yingliang <yangyingliang@...wei.com>
> Cc: Richard Cochran <richardcochran@...il.com>
> ---

I am not against this change, but I think this problem was discussed
before and the suggestions were to fix it differently:

https://lore.kernel.org/all/20210807144332.szyazdfl42abwzmd@skbuf/


Cheers,
-- 
Vinicius