Re: A question of perf NMI handler

From: Cyrill Gorcunov
Date: Wed Aug 04 2010 - 12:39:40 EST

On Wed, Aug 04, 2010 at 12:20:26PM -0400, Don Zickus wrote:
> > >
> > > Because the reason registers are never set. If they were, then the code
> > > wouldn't have to walk the notify_chain. :-)
> > >
> >
> > maybe we're talking about different things. i meant that if there is nmi
> > with a reason (from 0x61) the handling of such nmi should be done before
> > notify_die I think (if only I not miss something behind).
> No we are talking about the same thing. :-) And that code is already

seems not actually ;)

> there. The problem is the bits in register 0x61 are not always set
> correctly in the case of SERRs (well at least in all the cases I have
> dealt with). So you can easily can a flood of unknown nmis from an SERR
> and register 0x61 would have the PERR/SERR bits set to 0. Fun, huh?

if there is nothing in nmi_sc the code flows into another branch. And
it hits the problem of perf events eating all nmi giving no chance the
others. So we take if (!(reason & 0xc0)) case and hit DIE_NMI_IPI
(/me scratching the head why it's not under CONFIG_X86_LOCAL_APIC) and
drop all code, unpleasant.

> Cheers,
> Don
-- Cyrill
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