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SubjectRe: reason for delay in arch/x86/kernel/traps.c::io_check_error()?

* Chris Friesen <cfriesen@nortel.com> wrote:

> Hi all,
>
> I was just wondering about the basis for the delay in
> io_check_error(). The ICH7 manual doesn't have any mention of
> a delay being required here--is it necessary for other
> hardware, something not mentioned in the manual, or just an
> accident?

That code has seriously bitrotten along the years. All those
port 61H accesses:

arch/x86/kernel/traps.c: reason = get_nmi_reason();
arch/x86/kernel/traps.c: outb(reason, 0x61);
arch/x86/kernel/traps.c: outb(reason, 0x61);
arch/x86/kernel/traps.c: outb(reason, 0x61);

... are often wrong on modern chipsets - including the logic in
io_check_error(). But we dont really have lowlevel chipset
drivers on this level in Linux, so there's nothing suitable to
replace it with and it never got fixed.

Can you see this trigger on a box perhaps? Or are you worried
about the potential unbound execution time of this function
which can be up to 2 seconds in NMI context?

Ingo


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