linux-kernel - Re: [RFC/RFT patch 0/7] timekeeping: Unify clock MONOTONIC and clock BOOTTIME

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Message-ID: <2580c734d38041e984215ccc522a4f2d@genki.is>
Date:   Mon, 23 Apr 2018 20:40:36 -0400
From:   Genki Sky <sky@...ki.is>
To:     David Herrmann <dh.herrmann@...il.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [RFC/RFT patch 0/7] timekeeping: Unify clock MONOTONIC and clock BOOTTIME

  Hello,

I came across this thread for same reason as [0]: Daemons getting
killed by systemd on resume (after >WatchdogSec seconds of
suspending). I'm using master branch of systemd and the kernel. As
mentioned, systemd uses CLOCK_MONOTONIC, originally expecting it to
not include suspend time.

Correct me if I'm mistaken, but I don't see the ambiguity of whether
this patch series breaks systemd. If it's implemented correctly, you'd
hope it *would* break it!

As a random end user, I see three options to get suspend/resume
working again on my laptop:

(A) Change systemd to keep track of the difference between
CLOCK_MONOTONIC and CLOCK_MONOTONIC_ACTIVE, using their difference via
clock_gettime(). This seems to be what the author of this patch series
intends (?).

(B) Implement timerfd_*(2) for CLOCK_MONOTONIC_ACTIVE in the kernel.
Do a sed s/CLOCK_MONOTONIC/&_ACTIVE in systemd source code.

(C) Do a 90% reverting of this patch series. Just introduce
CLOCK_MONOTONIC_ACTIVE as the "what you should use", document and
publicize this fact, and sometime in the future (monotonically
speaking :) finally unify CLOCK_MONOTONIC and CLOCK_BOOTTIME.

Thoughts?

Also, agreed, the missing break in do_clock_gettime() should be fixed,
as David mentioned in [1]. Is someone already patching this?

[0]: http://lkml.kernel.org/r/CANq1E4Tf27FJHTrO4ZVtWhYK=DLmwzszK=njOpgXZZXqzAOunA@mail.gmail.com
[1]: http://lkml.kernel.org/r/CANq1E4QppGAaU5PYbGpuC00S6wGQcAt70Z7CntZHiLC6748z2A@mail.gmail.com

  Genki