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List:       netbsd-current-users
Subject:    Re: heartbeat panic by heavy traffic
From:       Manuel Bouyer <bouyer () antioche ! eu ! org>
Date:       2023-09-15 15:54:11
Message-ID: ZQR-I0KwMCRymUAk () mail ! soc ! lip6 ! fr
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On Fri, Sep 15, 2023 at 02:00:31PM -0000, Michael van Elst wrote:
> bouyer@antioche.eu.org (Manuel Bouyer) writes:
> 
> >But the clock softint shouldn't be locked out for 16s, ever.
> 
> Then the clock softint must have a higher priority than
> everything else including hard interrupts.
> 
> Obviously that's not how the system is designed, there
> are no limits on how long specific events may take and
> thus no guarantee for lower priority tasks to actually
> execute with a certain time. That would be some kind
> of real-time system.

But obviously such events are not expected to take a long time, or
they would have been deffered to lower priority, preemptible tasks.
Letting such events run for a long time wedges the system.

I still maintain that the bug here is the network soft interrupt running
for such a long time, without gigving a chance to other tasks

> 
> Such systems also rarely panic if they detect a violation
> of their rules.
> 
> In any case, locking out lower priority tasks by an
> overwhelmed network layer probably isn't the bug that
> we look for.

I disagree. And the heartbeat panic is here to help locate such bugs.

-- 
Manuel Bouyer <bouyer@antioche.eu.org>
     NetBSD: 26 ans d'experience feront toujours la difference
--
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