Messages in this thread | | | Date | Wed, 12 Sep 2012 10:53:12 -0400 | From | Prarit Bhargava <> | Subject | Re: [PATCH] time: Fix timeekeping_get_ns overflow on 32bit systems |
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On 09/11/2012 07:26 PM, John Stultz wrote: > Thomas: Please queue this in tip/timers/urgent for 3.6. > > Daniel Lezcano reported seeing multi-second stalls from > keyboard input on his T61 laptop when NOHZ and CPU_IDLE > were enabled on a 32bit kernel. > > He bisected the problem down to > 1e75fa8be9fb61e1af46b5b3b176347a4c958ca1 (time: Condense > timekeeper.xtime into xtime_sec). > > After reproducing this issue, I narrowed the problem down > to the fact that timekeeping_get_ns() returns a 64bit > nsec value that hasn't been accumulated. In some cases > this value was being then stored in timespec.tv_nsec > (which is a long). > > On 32bit systems, With idle times larger then 4 seconds > (or less, depending on the value of xtime_nsec), the > returned nsec value would overflow 32bits. This limited > kept time from increasing, causing timers to not expire. > > The fix is to make sure we don't directly store the > result of timekeeping_get_ns() into a tv_nsec field, > instead using a 64bit nsec value which can then be > added into the timespec via timespec_add_ns(). > > Cc: Ingo Molnar <mingo@kernel.org> > Cc: Richard Cochran <richardcochran@gmail.com> > Cc: Prarit Bhargava <prarit@redhat.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Daniel Lezcano <daniel.lezcano@linaro.org> > Reported-and-bisected-by: Daniel Lezcano <daniel.lezcano@linaro.org> > Tested-by: Daniel Lezcano <daniel.lezcano@linaro.org> > Signed-off-by: John Stultz <john.stultz@linaro.org>
Acked-by: Prarit Bhargava <prarit@redhat.com>
P.
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