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SubjectRe: [uml-devel] [UM] Long loop in __getnsdayoftime() after resume from ram
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Am 20.10.2014 10:27 schrieb Richard Weinberger <richard.weinberger@gmail.com>:
>
> On Sun, Oct 19, 2014 at 2:39 PM, Thomas Meyer <thomas@m3y3r.de> wrote:
> > Hello,
> >
> > in UML kernel I get a long cpu using loop in __getnstimeofday()
> > (kernel/time/timekeeping.c:315) in the call of timespec_add_ns(),
> > when I left the host kernel suspended to ram for a few hours and resume
> > again.
> > this is because it seems like the tk->xtime_sec wasn't updated yet, but
> > the nsecs were. nsecs can be as high as 8111000111000111000l
> >
> > the function timespec_add_ns() (include/linux/time.h:266) will call
> > __iter_div_u64_rem() which has an optimized loop for the case
> > that the dividend is not much bigger as the divisior.
> > but this isn't the case for resume from ram on the host kernel.
> >
> > any ideas how to fix this? is it possible to intercept the resume from
> > ram and update the timekeeper->xtime_sec somehow?
> > or can the um arch somehow overwrite timespec_add_ns() to always use
> > div_u64_rem() instead?
>
> Hmm, does this always happen?

Yes, my single core system seems to trigger this every time after resume from ram.

> At least on my notebook it did not happen. I've started an UML yesterday
> suspended it and after more than 12h it worked fine today.
>
> BTW: Do you see the issue also then freezing UML using the freezer cgroup?

I'm not sure what do you mean by this. Do I need to enable some special configs for this in the host or uml kernel?

> Would be easier to debug. :)
>
> --
> Thanks,
> //richard
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