Messages in this thread | | | Date | Fri, 15 Nov 2002 17:48:33 +0000 | From | John Levon <> | Subject | Re: NMI handling rework for x86 |
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On Fri, Nov 15, 2002 at 08:13:51AM -0600, Corey Minyard wrote:
> I don't think that's a good idea for two reasons: > > * If the oprofile code is only using the counter that the NMI > watchdog is not using, it will silently cause the NMI watchdog to > stop working. I know that's not the case now, but it could be in > the future.
Uh, this is fine. We always call the NMI watchdog handler, so it will see apic irqs get stuck, and work anyway.
> * The oprofile code will always reset the counter, so the NMI > watchdog will never see the timeout, so it doesn't matter.
wrong. If we are using counters 0 and 1, and 1 overflows, oprofile resets that, then 0 overflows, the NMI watchdog will see it and incorrectly reset it. You HAVE to avoid the reset - you can test it if you don't believe me.
> It's currently kind of an unnatural relationship. IMHO, it would be > better to have a separate handler for the perf counters that they both > use. But that's beyond the scope of this right now.
Yes.
> +/* This is for I/O APIC, until we can figure out how to tell if it's from the > + I/O APIC. If the NMI was not handled before now, we handle it. */ > +static int dummy_watchdog_reset(int handled) > +{ > + return !handled; > +}
And if it was handled previously, you reset it to not handled ? Uh ?
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