Messages in this thread | | | Date | Tue, 18 Jun 2019 15:46:54 -0700 | From | Ricardo Neri <> | Subject | Re: [RFC PATCH v4 12/21] watchdog/hardlockup/hpet: Adjust timer expiration on the number of monitored CPUs |
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On Tue, Jun 11, 2019 at 10:11:04PM +0200, Thomas Gleixner wrote: > On Thu, 23 May 2019, Ricardo Neri wrote: > > @@ -52,10 +59,10 @@ static void kick_timer(struct hpet_hld_data *hdata, bool force) > > return; > > > > if (hdata->has_periodic) > > - period = watchdog_thresh * hdata->ticks_per_second; > > + period = watchdog_thresh * hdata->ticks_per_cpu; > > > > count = hpet_readl(HPET_COUNTER); > > - new_compare = count + watchdog_thresh * hdata->ticks_per_second; > > + new_compare = count + watchdog_thresh * hdata->ticks_per_cpu; > > hpet_set_comparator(hdata->num, (u32)new_compare, (u32)period); > > So with this you might get close to the point where you trip over the SMI > induced madness where CPUs vanish for several milliseconds in some value > add code. You really want to do a read back of the hpet to detect that. See > the comment in the hpet code. RHEL 7/8 allow up to 768 logical CPUs....
Do you mean adding a readback to check if the new compare value is greater than the current count? Similar to the check at the end of hpet_next_event():
return res < HPET_MIN_CYCLES ? -ETIME : 0;
In such a case, should it try to set the comparator again? I think it should, as otherwise the hardlockup detector would stop working.
Thanks and BR, Ricardo > > Thanks, > > tglx
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