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

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Date:   Fri, 30 Oct 2020 10:02:29 -0400
From:   Zack Weinberg <zackw@...ix.com>
To:     Cyril Hrubis <chrubis@...e.cz>
Cc:     Lukasz Majewski <lukma@...x.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrei Vagin <avagin@...il.com>,
        GNU C Library <libc-alpha@...rceware.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Dmitry Safonov <dima@...sta.com>
Subject: Re: [Y2038][time namespaces] Question regarding CLOCK_REALTIME
 support plans in Linux time namespaces

On Fri, Oct 30, 2020 at 9:57 AM Cyril Hrubis <chrubis@...e.cz> wrote:
> > 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.
...
> > To be more specific - [if this were supported] 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.
>
> And what's exactly wrong with moving the system time forward for a
> duration of the test?

Interference with other processes on the same computer?  Some of us
*do* like to run the glibc test suite on computers not entirely
devoted to glibc CI.

zw