Re: smp_call_function_single lockups

[Linus Torvalds]

On Thu, Apr 2, 2015 at 2:55 AM, Ingo Molnar <mingo@xxxxxxxxxx> wrote:
>
> So another possibility would be that it's the third change causing
> this change in behavior:

Oh, yes, that looks much more likely. I overlooked that small change entirely.

> ... since with this we won't send IPIs in a semi-nested fashion with
> an unacked APIC, which is a good idea to do in general. It's also a
> weird enough hardware pattern that virtualization's APIC emulation
> might get it slightly wrong or slightly different.

Yup, that's more likely than the subtle timing/reordering differences
of just the added debug printouts. I agree.

                             Linus
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