2016-01-26 23:21 GMT+08:00 Thomas Gleixner <[email protected]>: > On Thu, 21 Jan 2016, Wanpeng Li wrote: > >> After commit 0ff53d096422 ("tick: sched: Force tick interrupt and get rid >> of softirq magic"), next expire time is overwritten by last_jiffies_update >> while switch to low-res nohz mode which leads to jiffies warp. This patch >> fix it by programming ce device the expire time in the future. > >> - hrtimer_forward_now(&ts->sched_timer, tick_period); >> hrtimer_set_expires(&ts->sched_timer, next); >> - tick_program_event(next, 1); >> + hrtimer_forward_now(&ts->sched_timer, tick_period); >> + tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1); >> tick_nohz_activate(ts, NOHZ_MODE_LOWRES); > > I agree, that the ordering forward/set is wrong and needs to be fixed, but how > does that result in a jiffies warp? > > tick_nohz_handler() > tick_sched_do_timer() > tick_do_update_jiffies64() > delta = ktime_sub(now, last_jiffies_update); > if (delta.tv64 < tick_period.tv64) > return;
Yeah, I know this catch it and that's why no real warp happen, just send out v2, thanks for your review, Thomas. :-) Regards, Wanpeng Li
