linux-kernel - Re: [PATCH v2 1/2] time/timekeeping: Fix possible inconsistencies in

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Message-ID: <877c41wkis.ffs@tglx>
Date: Thu, 03 Apr 2025 13:29:31 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Miroslav Lichvar <mlichvar@...hat.com>
Cc: John Stultz <jstultz@...gle.com>, LKML <linux-kernel@...r.kernel.org>,
 Stephen Boyd <sboyd@...nel.org>, Anna-Maria Behnsen
 <anna-maria@...utronix.de>, Frederic Weisbecker <frederic@...nel.org>,
 Shuah Khan <shuah@...nel.org>, linux-kselftest@...r.kernel.org,
 kernel-team@...roid.com, Lei Chen <lei.chen@...rtx.com>
Subject: Re: [PATCH v2 1/2] time/timekeeping: Fix possible inconsistencies
 in _COARSE clockids

On Thu, Apr 03 2025 at 10:32, Miroslav Lichvar wrote:
> On Tue, Apr 01, 2025 at 08:29:23PM +0200, Thomas Gleixner wrote:
>> > 64		64		0.138
>> 
>> That's weird as it only delays the update to the next tick.
>
> Ok, so it's not an instability of the clock, but rather an instability
> of the chronyd synchronization loop, which since kernel 4.19 expects
> the frequency to be applied as soon as the adjtimex call is finished.

Interesting.

>> Patch applies after reverting 757b000f7b93 ("timekeeping: Fix possible
>> inconsistencies in _COARSE clockids").
>
> I ran multiple longer tests to be able to compare the small values in
> the noise and yes, from the adjtimex point of view this seems to work
> as well as before the first COARSE fix. I didn't run any tests of the
> COARSE clock.

I did run those, but did not run the adjtimex() muck :)