Re: [net] devlink: Add method for time-stamp on reporter's dump

Arnd Bergmann
2019-08-22T19:12:03Z

On Thu, Aug 22, 2019 at 7:40 PM Ido Schimmel <idosch@idosch.org> wrote:
> On Thu, Aug 22, 2019 at 04:06:35PM +0200, Andrew Lunn wrote:
> > On Thu, Aug 22, 2019 at 11:17:51AM +0300, Aya Levin wrote:
> > > When setting the dump's time-stamp, use ktime_get_real in addition to
> > > jiffies. This simplifies the user space implementation and bypasses
> > > some inconsistent behavior with translating jiffies to current time.
> >
> > Is this year 2038 safe? I don't know enough about this to answer the
> > question myself.
>
> Good point. 'struct timespec' is not considered year 2038 safe and
> unfortunately I recently made the mistake of using it to communicate
> timestamps to user space over netlink. :/ The code is still in net-next,
> so I will fix it while I can.
>
> Arnd, would it be acceptable to use 'struct __kernel_timespec' instead?

The in-kernel representation should just use 'timespec64' if you need
separate seconds and nanoseconds, you can convert that to
__kernel_timespec while copying to user space.

However, please consider two other points:

- for simplicity, the general recommendation is to use 64-bit nanoseconds
without separate seconds for timestamps
- instead of CLOCK_REALTIME, you could use CLOCK_MONOTONIC
timestamps that are not affected by clock_settime() or leap second jumps.

Arnd