lkml.org 
[lkml]   [2019]   [Aug]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: New kernel interface for sys_tz and timewarp?
Date
* 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 settings for of this, as 'struct timezone' is obsolete/vestigial and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.

Maybe it is possible to replace these things with other mechanisms
which exist today. For example, the mount program could read a
configuration file to determine the system default for the time_offset
mount option and apply the value automatically. The real-time clock
offset could be maintained by whatever mechanism hwclock uses.

I think whatever we end up doing, we should maintain consistency after
a system upgrade after architectures. It does not make sense to keep
using the settimeofday hack on amd64 indefinitely, and switch to a
different mechanism on RV32, so that the two ways of supplying the
offset are never reconciled across architectures.

\
 
 \ /
  Last update: 2019-08-13 21:31    [W:0.096 / U:0.168 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site