linux-kernel - [Y2038][time namespaces] Question regarding CLOCK_REALTIME support plans in Linux time namespaces

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Message-ID: <20201030110229.43f0773b@jawa>
Date:   Fri, 30 Oct 2020 11:02:29 +0100
From:   Lukasz Majewski <lukma@...x.de>
To:     Andrei Vagin <avagin@...il.com>, Dmitry Safonov <dima@...sta.com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     GNU C Library <libc-alpha@...rceware.org>,
        Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org
Subject: [Y2038][time namespaces] Question regarding CLOCK_REALTIME support
 plans in Linux time namespaces

Hi Andrei, Dmitry,

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?

Why I'm asking? 

It looks like this kernel feature (with CLOCK_REALTIME support
available) would be very helpful for testing Y2038 compliance for e.g.
glibc 32 bit ports.

To be more specific - it would be possible to modify time after time_t
32 bit overflow (i.e. Y2038 bug) on the process running Y2038
regression tests on the host system (64 bit one). By using Linux time
namespaces the system time will not be affected in any way.

Thanks in advance for your help.

Links:

[1] - https://lkml.org/lkml/2019/10/10/1329
[2] - https://www.man7.org/linux/man-pages/man7/time_namespaces.7.html

Best regards,

Lukasz Majewski

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