From: Arnd Bergmann <arnd@arndb.de>
To: Florian Weimer <fw@deneb.enyo.de>
Cc: Paul Eggert <eggert@cs.ucla.edu>,
Linus Torvalds <torvalds@linux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
John Stultz <john.stultz@linaro.org>,
Alexandre Belloni <alexandre.belloni@bootlin.com>,
Stephen Boyd <sboyd@kernel.org>,
Florian Weimer <fweimer@redhat.com>,
"Theodore Ts'o" <tytso@mit.edu>, "H. Peter Anvin" <hpa@zytor.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Alistair Francis <alistair.francis@wdc.com>,
GNU C Library <libc-alpha@sourceware.org>,
Karel Zak <kzak@redhat.com>,
Lennart Poettering <lennart@poettering.net>,
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Subject: Re: New kernel interface for sys_tz and timewarp?
Date: Tue, 13 Aug 2019 22:04:05 +0200 [thread overview]
Message-ID: <CAK8P3a13f7an3xkQcP7qcSR-yhp=wYMT_cJ9h7gEdB3Qk8chBw@mail.gmail.com> (raw)
In-Reply-To: <87tvakuak6.fsf@mid.deneb.enyo.de>
On Tue, Aug 13, 2019 at 9:31 PM Florian Weimer <fw@deneb.enyo.de> wrote:
> * Paul Eggert:
> > Linus Torvalds wrote:
> >> I assume/think that glibc uses (a) environment
> >> variables and (b) a filesystem-set default (per-user file with a
> >> system-wide default? I don't know what people do).
>
> > glibc relies on the TZ environment variable, with a system-wide
> > default specified in /etc/localtime or suchlike (there is no
> > per-user default). glibc ignores the kernel's 'struct timezone'
> > settings for of this, as 'struct timezone' is obsolete/vestigial and
> > doesn't contain enough info to do proper conversions anyway.
>
> I think the configuration value that settimeofday changes is not
> actually a time zone, but an time offset used to interpret various
> things, mostly in a dual-boot environment with Windows, apparently
> (Like the default time offset for extracting timetamps from FAT
> volumes.)
>
> This data has to come from *somewhere*. The TZ variable and
> /etc/localtime cover something else entirely.
systemd and hwclock call localtime_r() when setting initial
system time an tz information at boot time, so that information
comes from /etc/localtime.
/etc/adjtime is used to determine whether to set warp the
time at boot and rtc update or not warp it.
Arnd
next prev parent reply other threads:[~2019-08-13 20:04 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-13 9:05 New kernel interface for sys_tz and timewarp? Arnd Bergmann
2019-08-13 17:10 ` John Stultz
2019-08-13 21:45 ` Alexandre Belloni
2019-08-13 17:30 ` Linus Torvalds
2019-08-13 17:49 ` Paul Eggert
2019-08-13 19:31 ` Florian Weimer
2019-08-13 20:04 ` Arnd Bergmann [this message]
2019-08-13 21:56 ` Alexandre Belloni
2019-08-14 0:06 ` Theodore Y. Ts'o
2019-08-14 8:31 ` Arnd Bergmann
2019-08-14 9:09 ` Lennart Poettering
2019-08-14 9:32 ` Alexandre Belloni
2019-08-14 12:15 ` Lennart Poettering
2019-08-19 11:09 ` Karel Zak
2019-08-19 13:43 ` Thomas Gleixner
2019-08-19 13:49 ` Thomas Gleixner
2019-08-20 18:45 ` Alexandre Belloni
2019-08-20 18:47 ` Alexandre Belloni
2019-08-20 18:58 ` Alexandre Belloni
2019-08-27 16:27 ` Arnd Bergmann
2019-08-27 16:31 ` Alexandre Belloni
2019-08-14 16:26 ` David Laight
2019-08-14 16:47 ` hpa
2019-08-15 13:22 ` Arnd Bergmann
2019-08-15 15:05 ` Theodore Y. Ts'o
2019-08-15 15:24 ` hpa
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