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 <mi...@kernel.org> > Cc: Richard Cochran <richardcoch...@gmail.com> > Cc: Prarit Bhargava <pra...@redhat.com> > Cc: Thomas Gleixner <t...@linutronix.de> > Cc: Daniel Lezcano <daniel.lezc...@linaro.org> > Reported-and-bisected-by: Daniel Lezcano <daniel.lezc...@linaro.org> > Tested-by: Daniel Lezcano <daniel.lezc...@linaro.org> > Signed-off-by: John Stultz <john.stu...@linaro.org>
Acked-by: Prarit Bhargava <pra...@redhat.com> P. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
