Messages in this thread | | | Date | Tue, 23 Feb 2021 16:53:06 +0100 (CET) | From | Anna-Maria Behnsen <> | Subject | Re: Sv: [PATCH] hrtimer: Interrupt storm on clock_settime |
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Hi Micke,
On Fri, 12 Feb 2021, Beckius, Mikael wrote:
> Thanks for the update and sorry for the late reply. After long-term > testing of the patch, storm detection improved, it turns out that a > similar problem can occur if hrtimer_interrupt runs during > clock_settime. In this case it seems the offset can get updated and later > read using hrtimer_update_base in hrtimer_interrupt before > softirq_expires_next gets updated. As soon as softirq_expires_next gets > updated by hrtimer_force_reprogram the storm ends. To fix this I made the > below changes. > > --- a/kernel/time/hrtimer.c > +++ b/kernel/time/hrtimer.c > @@ -529,8 +529,10 @@ static ktime_t __hrtimer_next_event_base(struct hrtimer_cpu_base *cpu_base, > if (exclude) > continue; > > - if (timer->is_soft) > + if (timer->is_soft) { > cpu_base->softirq_next_timer = timer; > + cpu_base->softirq_expires_next = expires; > + } > else > cpu_base->next_timer = timer; > } > @@ -633,19 +635,6 @@ hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base, int skip_equal) > */ > expires_next = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_ALL); > > - if (cpu_base->next_timer && cpu_base->next_timer->is_soft) { > - /* > - * When the softirq is activated, hrtimer has to be > - * programmed with the first hard hrtimer because soft > - * timer interrupt could occur too late. > - */ > - if (cpu_base->softirq_activated) > - expires_next = __hrtimer_get_next_event(cpu_base, > - HRTIMER_ACTIVE_HARD); > - else > - cpu_base->softirq_expires_next = expires_next; > - } > - > if (skip_equal && expires_next == cpu_base->expires_next) > return; > > -- >
The proposed change breaks the reprogramming logic. To keep it working cpu_base::*expires_next is only updated by hrtimer_reprogram() and hrtimer_interrupt(). I will send you a patch for testing in reply to this thread. The patch is compile tested only.
Thanks,
Anna-Maria
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