netdev - Re: [PATCH net 1/4] ice: Create a separate kthread to handle ptp extts work

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Date:   Mon, 12 Dec 2022 23:24:22 +0000
From:   "Kolacinski, Karol" <karol.kolacinski@...el.com>
To:     "richardcochran@...il.com" <richardcochran@...il.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "G, GurucharanX" <gurucharanx.g@...el.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>
Subject: Re: [PATCH net 1/4] ice: Create a separate kthread to handle ptp
 extts work

>On 12/7/2022 4:27 PM, Richard Cochran wrote:
>> On Wed, Dec 07, 2022 at 01:10:37PM -0800, Tony Nguyen wrote:
>>> From: Anatolii Gerasymenko anatolii.gerasymenko@...el.com
>>>
>>> ice_ptp_extts_work() and ice_ptp_periodic_work() are both scheduled on
>>> the same kthread_worker pf.ptp.kworker. But, ice_ptp_periodic_work()
>>> sends messages to AQ and waits for responses. This causes
>>> ice_ptp_extts_work() to be blocked while waiting to be scheduled. This
>>> causes problems with the reading of the incoming signal timestamps,
>>> which disrupts a 100 Hz signal.
>>>
>>> Create an additional kthread_worker pf.ptp.kworker_extts to service only
>>> ice_ptp_extts_work() as soon as possible.
>> 
>> Looks like this driver isn't using the do_aux_work callback.  That
>> would provide a kthread worker for free.  Why not use that?

According to do_aux_work description, it is used to do 'auxiliary (periodic)
operations'.
ice_ptp_extts_work is not exactly periodic as the work is queued only when the
interrupt comes.

Thanks,
Karol