On 22/02/2016 at 17:18:03 +0100, Arnd Bergmann wrote :

quoted

quoted

IIRC, the problem is that user space passes in TIME_T_MAX and the kernel
is considering that to be in the past because the clock is set beyond 2038.

I find it hard to blame user space for that, but I don't have a good
idea for solving this either.

In case of systemd, it is literally the first thing that runs on the kernel
after booting, so we could fall back to setting the time to some known
working state (1970 or 2016 or something), but that would be a rather
bad default policy once the system has been running for a while.

Also, how would you know that it is an invalid time, some RTC doesn't
provide that information. 

What I meant was encountering a time past the 2038 date, which is invalid
as seen from current 32-bit user space, but not necessarily from the
kernel.

I'm not completely sure how this would be different from my current patch...

quoted

One other workaround is to asked distributions
using systemd to stop using HCTOSYS so userspace would be responsible to
set the system time and in that case we won't have the 32/64 discrepancy.

I'm missing a bit of background here. This seems like a fairly useful
piece of infrastructure for the majority of the use cases (working RTC)

How would the time get set when this is disabled? Is systemd able
to read the rtc and write it back to the kernel? That could in fact
be a nicer workaround for the problem, if it just does this before
setting up the timerfd.

I didn't check other distribution but debian and poky have
/etc/init.d/hwclock.sh that reads the rtc and sets the system time at
startup. It also saves the time to the RTC on shutdown.


-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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