Messages in this thread | | | Subject | Re: [PATCH v3 03/14] sched/core: uclamp: add CPU's clamp groups accounting | From | Dietmar Eggemann <> | Date | Thu, 16 Aug 2018 17:00:44 +0200 |
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On 08/16/2018 04:21 PM, Quentin Perret wrote: > On Thursday 16 Aug 2018 at 15:45:45 (+0200), Dietmar Eggemann wrote: >> On 08/16/2018 03:37 PM, Quentin Perret wrote: >>>>> IMHO, if this is something which should not happen at all, a BUG_ON() is the >>>>> right thing to do here. >>>> >>>> I don't agree on that. I agree it should not happen but since it's a >>>> recoverable error it think we should not panic. >>> >>> FWIW, if this is a recoverable error, I think Linus will agree with >>> Patrick on this one :-) >>> >>> https://lkml.org/lkml/2016/10/4/1 >> >> Yeah, not really agreeing here that this is a recoverable error. > > A non-recoverable scenario could be, for example, if you corrupt your > stack and there is absolutely _nothing_ you can do to keep the system up > and running, because it's just too broken. I don't feel like we're > talking about such an extreme case here ...
Yeah, that's the extreme. But what about this lovely BUG_ON(busiest == env.dst_rq) in fair.c's load_balance()?
We could recover by just bailing out ;-)
I guess we know by now that there are different opinions here.
> >> Besides, we >> only consider under-run here, what about over-run?
Important thing is to also detect the over-run, i.e. add the first task and the task counter is already > 0.
>> >> Currently this warning doesn't hit and if the code will be changed and it >> hits, I still find a BUG_ON more appealing here ... >> >> So this error scenario can happen over and over again and we always recover >> from ? The important thing is that we find the culprit for this behaviour as >> fast as possible ... > > Agreed, we want to debug that ASAP, but WARN should let us do that just > fine, I think.
+1.
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