From: Lukasz Majewski <lukma@denx.de>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrei Vagin <avagin@gmail.com>, Dmitry Safonov <dima@arista.com>,
GNU C Library <libc-alpha@sourceware.org>,
Arnd Bergmann <arnd@arndb.de>,
linux-kernel@vger.kernel.org
Subject: Re: [Y2038][time namespaces] Question regarding CLOCK_REALTIME support plans in Linux time namespaces
Date: Fri, 30 Oct 2020 16:43:37 +0100 [thread overview]
Message-ID: <20201030164337.347fe961@jawa> (raw)
In-Reply-To: <871rhfoo7z.fsf@nanos.tec.linutronix.de>
[-- Attachment #1: Type: text/plain, Size: 1839 bytes --]
Hi Thomas,
> Lukasz,
>
> On Fri, Oct 30 2020 at 11:02, Lukasz Majewski wrote:
> > I do have a question regarding the Linux time namespaces in respect
> > of adding support for virtualizing the CLOCK_REALTIME.
> >
> > According to patch description [1] and time_namespaces documentation
> > [2] the CLOCK_REALTIME is not supported (for now?) to avoid
> > complexity and overhead in the kernel.
> >
> > Is there any plan to add support for it in a near future?
>
> Not really. Just having an offset on clock realtime would be incorrect
> in a number of ways. Doing it correct is a massive trainwreck.
>
> For a debug aid, which is what you are looking for, the correctness
> would not really matter, but providing that is a really slippery
> slope.
>
> If at all we could hide it under a debug option which depends on
> CONFIG_BROKEN and emitting a big fat warning in dmesg with a clear
> statement that it _is_ broken, stays so forever and any attempt to
> "fix" it results in a permanent ban from all kernel lists.
>
> Preferrably we don't go there.
I see. Thanks for the explanation.
Now, I do use QEMU to emulate ARM 32 bit system with recent kernel
(5.1+). It works.
Another option would be to give a shoot to QEMU with the "user mode" to
run cross-compiled tests (with using a cross-compiled glibc in earlier
CI stage). The problem with above is the reliance on QEMU emulation of
ARM syscalls (and if 64 bit time supporting syscalls - i.e.
clock_settime64 - are available).
>
> Thanks,
>
> tglx
>
>
Best regards,
Lukasz Majewski
--
DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de
[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 488 bytes --]
next prev parent reply other threads:[~2020-10-30 15:44 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-30 10:02 Lukasz Majewski
2020-10-30 13:08 ` Thomas Gleixner
2020-10-30 15:43 ` Lukasz Majewski [this message]
2020-10-30 13:58 ` Cyril Hrubis
2020-10-30 14:02 ` Zack Weinberg
2020-10-30 15:10 ` Thomas Gleixner
2020-10-30 16:58 ` Carlos O'Donell
2020-10-30 20:06 ` Thomas Gleixner
2020-10-30 22:19 ` Carlos O'Donell
2020-10-31 1:38 ` Thomas Gleixner
2020-11-03 12:43 ` Cyril Hrubis
2020-11-05 17:25 ` Carlos O'Donell
2020-11-07 0:47 ` Thomas Gleixner
2020-11-19 18:37 ` Carlos O'Donell
2020-11-20 0:14 ` Thomas Gleixner
2020-11-25 17:06 ` Petr Špaček
2020-11-25 20:37 ` Carlos O'Donell
2020-11-26 0:17 ` Thomas Gleixner
2020-11-26 3:05 ` Carlos O'Donell
2020-11-26 8:21 ` Andreas Schwab
2020-11-19 12:08 ` Petr Špaček
2020-11-14 10:25 ` Pavel Machek
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20201030164337.347fe961@jawa \
--to=lukma@denx.de \
--cc=arnd@arndb.de \
--cc=avagin@gmail.com \
--cc=dima@arista.com \
--cc=libc-alpha@sourceware.org \
--cc=linux-kernel@vger.kernel.org \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).