linux-kernel - Re: Question on expiring HRtimer in-kernel

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Message-ID: <CACRpkdai4+1NJ+UJxdcEHJjKtccE=LnDyv7pr1pzuQo88-MdaQ@mail.gmail.com>
Date:   Thu, 3 Mar 2022 23:55:11 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Matti Vaittinen <mazziesaccount@...il.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Anna-Maria Gleixner <anna-maria@...utronix.de>,
        Sebastian Reichel <sre@...nel.org>,
        Code Kipper <codekipper@...il.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: Question on expiring HRtimer in-kernel

On Thu, Mar 3, 2022 at 1:43 PM Matti Vaittinen <mazziesaccount@...il.com> wrote:

> In any case, I remember few cases where I hit nasty issues because I
> used CLOCK_REALTIME - which (AFAIR) is subject to the time adjustments.
> NTP, GPS-time and so on can make the time tick in a strange way :) I
> guess you would have noticed if time was set when timer did expire.
>
> Anyways, I guess the battery charging should rather be tied CLOCK_MONOTONIC.

That makes a lot of sense, and is what I have learned from the internal
kernel primitives as well, I just assumed the HRTimer was some special
kind of beast.

I'll patch this and run some testing, if it goes away with MONOTONIC
I'll send a patch. Thanks!

Yours,
Linus Walleij