Messages in this thread | | | Date | Wed, 26 Nov 2014 13:28:11 -0800 | Subject | Re: [time] WARNING: CPU: 0 PID: 1 at kernel/time/timekeeping.c:1337 update_wall_time() | From | John Stultz <> |
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On Wed, Nov 26, 2014 at 12:00 PM, Fengguang Wu <fengguang.wu@intel.com> wrote: > Greetings, > > 0day kernel testing robot got the below dmesg and the first bad commit is > > git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master > > commit 6067dc5a8c2b1b57e67eaf1125db1d63c1ed6361 > Author: pang.xunlei <pang.xunlei@linaro.org> > AuthorDate: Wed Oct 8 15:03:34 2014 +0800 > Commit: John Stultz <john.stultz@linaro.org> > CommitDate: Fri Nov 21 11:59:56 2014 -0800 > > time: Avoid possible NTP adjustment mult overflow. > > Ideally, __clocksource_updatefreq_scale, selects the largest shift > value possible for a clocksource. This results in the mult memember of > struct clocksource being particularly large, although not so large > that NTP would adjust the clock to cause it to overflow. > > That said, nothing actually prohibits an overflow from occuring, its > just that it "shouldn't" occur. > > So while very unlikely, and so far never observed, the value of > (cs->mult+cs->maxadj) may have a chance to reach very near 0xFFFFFFFF, > so there is a possibility it may overflow when doing NTP positive > adjustment > > See the following detail: When NTP slewes the clock, kernel goes > through update_wall_time()->...->timekeeping_apply_adjustment(): > tk->tkr.mult += mult_adj; > > Since there is no guard against it, its possible tk->tkr.mult may > overflow during this operation. > > This patch avoids any possible mult overflow by judging the overflow > case before adding mult_adj to mult, also adds the WARNING message > when capturing such case. > > Signed-off-by: pang.xunlei <pang.xunlei@linaro.org> > [jstultz: Reworded commit message] > Signed-off-by: John Stultz <john.stultz@linaro.org>
So you caught this false-positive issue in my tree, unfortunately just mintes before it was pulled into -tip. :)
I've since submitted a fix which was pulled into -tip just the other day, but looks like it isn't yet in the current -next. See: http://git.kernel.org/cgit/linux/kernel/git/tip/tip.git/commit/?h=timers/core&id=cb2aa63469f81426c7406227be70b628b42f7a05
It should go away as soon as that patch lands in -next, but do let me know if you continue to see this.
thanks -john
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