Re: New kernel interface for sys_tz and timewarp?

Lennart Poettering
2019-08-14T09:17:49Z

On Mi, 14.08.19 10:31, Arnd Bergmann (arnd@arndb.de) wrote:

> - glibc stops passing the caller timezone argument to the kernel
> - the distro kernel disables CONFIG_RTC_HCTOSYS,
> CONFIG_RTC_SYSTOHC and CONFIG_GENERIC_CMOS_UPDATE

What's the benefit of letting userspace do this? It sounds a lot more
fragile to leave this syncing to userspace if the kernel can do this
trivially on its own.

IIRC there are uses in kernel that use CLOCK_REALTIME already before
userspace starts. e.g. iirc networking generally prefers
CLOCK_REALTIME timestamps over CLOCK_MONOTONIC timestamps
(i.e. SO_TIMESTAMP and friends are still CLOCK_REALTIME only so far,
unless I am missing something). If the kernel comes up with a
CLOCK_REALTIME that starts at 0 this is pretty annoying I
figure... Hence, so far I suggested to distros to continue turning on
the options above, and let the kernel do this on its own without
involving userspace in that.

Lennart

--
Lennart Poettering, Berlin