linux-kernel - Re: [PATCH] rtc: adapt allowed RTC update error

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Message-ID: <87eek8dphc.fsf@nanos.tec.linutronix.de>
Date:   Wed, 02 Dec 2020 19:36:47 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Miroslav Lichvar <mlichvar@...hat.com>
Cc:     Jason Gunthorpe <jgg@...pe.ca>, linux-kernel@...r.kernel.org,
        John Stultz <john.stultz@...aro.org>,
        Prarit Bhargava <prarit@...hat.com>
Subject: Re: [PATCH] rtc: adapt allowed RTC update error

On Wed, Dec 02 2020 at 16:36, Miroslav Lichvar wrote:
> On Wed, Dec 02, 2020 at 04:07:28PM +0100, Miroslav Lichvar wrote:
>> On Wed, Dec 02, 2020 at 02:44:53PM +0100, Thomas Gleixner wrote:
>> > Something like the completely untested below should make this reliable
>> > and only needs to retry when the work is running late (busy machine),
>> > but the wakeup will be on time or at max 1 jiffie off when high
>> > resolution timers are not available or disabled.
>> 
>> It seems to work nicely. In my test most of the updates succeeded on
>> the first attempt hitting the right tick, the rest succeeding on the
>> second attempt. Only when the clock was set to run 10% faster, it
>> needed few more attempts to converge to the target time.
>
> I noticed an observable change wrt adjtimex() calls though. It seems
> it now reschedules the RTC update, i.e. there can be more than one
> update per 11 minutes. Was this intended?

No. Let me fix that.

Thanks,

        tglx