Thanks Shane, queued for crash-7.1.8: https://github.com/crash-utility/crash/commit/fe63125327e6b8b04d6723656bfd263453a87dc9 Dave ----- Original Message ----- > Hi Dave, > > I've been staring at an issue in crash all afternoon trying to work out what > happened to the current clock value printed by timer -r. I've got output > from the timer -r command that looks like (the vmcore has 315+ days of > uptime) this: > > CPU: 0 HRTIMER_CPU_BASE: ffff883f7fa0d7a0 > CLOCK: 0 HRTIMER_CLOCK_BASE: ffff883f7fa0d7e0 [ktime_get] > CURRENT > 9017759896290448 > SOFTEXPIRES EXPIRES HRTIMER FUNCTION > 27464498630000000 27464498630000000 ffff883f7fa0da40 ffffffff810d0440 > <tick_sched_timer> > 27464498643441992 27464498643491992 ffff880243f5bd60 ffffffff8109ae70 > <hrtimer_wakeup> > 27464498690255938 27464498690755937 ffff8842d7c1b908 ffffffff8109ae70 > <hrtimer_wakeup> > ... > > The time under the CURRENT heading is way less than the softexpires/expires > which really didn't look correct so I dug into the crash code and found that > the calculation in dump_hrtimer_clock_base() can overflow for a largish > value of current_time (I did the calculations involved in working out what > current_time was by hand to make sure that they would overflow and they did, > but I haven't included those workings). The value above works out to be the > amount over the maximum value of an unsigned 64bit in that would have been > calculated (i.e. it wrapped). > > When I changed it from: > > now = current_time * 1000000000LL / machdep->hz + offset; > > to > > now = current_time * (1000000000LL / machdep->hz) + offset; > > It works as I expected it to. I've tested with that change and the fixed > output is: > > CPU: 0 HRTIMER_CPU_BASE: ffff883f7fa0d7a0 > CLOCK: 0 HRTIMER_CLOCK_BASE: ffff883f7fa0d7e0 [ktime_get] > CURRENT > 27464503970000000 > SOFTEXPIRES EXPIRES HRTIMER FUNCTION > 27464498630000000 27464498630000000 ffff883f7fa0da40 ffffffff810d0440 > <tick_sched_timer> > 27464498643441992 27464498643491992 ffff880243f5bd60 ffffffff8109ae70 > <hrtimer_wakeup> > 27464498690255938 27464498690755937 ffff8842d7c1b908 ffffffff8109ae70 > <hrtimer_wakeup> > > There's a second one in dump_hrtimer_base(): > > now = current_time * 1000000000LL / machdep->hz; > > that may have similar issues but it wasn't impacting on the vmcore I was > looking at but I changed it anyway. > > Thanks > Shane > > P.S. cut and pasted the diff output not sure if it's going to work correctly > or not because of that. > --- > --- a/kernel.c 2016-11-30 13:56:29.000000000 -0500 > +++ b/kernel.c 2017-02-06 02:23:35.179164828 -0500 > @@ -7263,7 +7263,7 @@ dump_hrtimer_clock_base(const void *hrti > offset = 0; > if (VALID_MEMBER(hrtimer_clock_base_offset)) > offset = ktime_to_ns(base + > OFFSET(hrtimer_clock_base_offset)); > - now = current_time * 1000000000LL / machdep->hz + offset; > + now = current_time * (1000000000LL / machdep->hz) + offset; > > dump_active_timers(base, now); > } > @@ -7285,7 +7285,7 @@ dump_hrtimer_base(const void *hrtimer_ba > > /* get current time(uptime) */ > get_uptime(NULL, ¤t_time); > - now = current_time * 1000000000LL / machdep->hz; > + now = current_time * (1000000000LL / machdep->hz); > > dump_active_timers(base, now); > } > > -- > Crash-utility mailing list > Crash-utility@xxxxxxxxxx > https://www.redhat.com/mailman/listinfo/crash-utility > -- Crash-utility mailing list Crash-utility@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/crash-utility
