Re: [PATCH] x86_64: avoid sending LOCAL_TIMER_VECTOR IPI to itself

Ingo Molnar
2007-03-24T19:12:31Z

* Ray Lee <ray-lk@madrabbit.org> wrote:

> Subject: [PATCH] x86_64: avoid sending LOCAL_TIMER_VECTOR IPI to
> itself
>
> Ray Lee reported, that on an UP kernel with "noapic" command line
> option set, the box locks hard during boot.

i think this bug deserves a bit more attention, because similar problems
could be in other codepaths too.

the problem here is that we tried to send an IPI to ourselves - which
confused Ray's system which has an IO-APIC, but where due to noapic we
keep the IO-APIC in its BIOS default.

this isnt a new problem: the new time code just exposed it more
prominently that it was visible before. (the SMP kernel probably would
hang in a similar way on Ray's system)

i dont see any clear debugging in the IPI code that excludes self-IPIs.
I think the only valid way to do that is to use DEST_SELF. Andi?

Ingo