[uml-user] Long loop in __getnsdayoftime() after resume from ram

[Thomas M. <th...@m3...>]

Hello,

in UML kernel 3.16.1 I get a long loop in __getnstimeofday()
(kernel/time/timekeeping.c:315) in the call of timespec_add_ns(),
because it seems like the tk->xtime_sec wasn't updated yet, but the
nsecs were. nsecs can be as high as 8111000111000111000l when left the
host kernel suspended to ram over night.

then 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?

how does the host kernel deal with this? are there some .suspend/.resume
callbacks missing in the um "itimer" clocksource?

with kind regards
thomas