Re: smp_call_function_single lockups

From: Ingo Molnar
Date: Sun Feb 22 2015 - 05:37:24 EST

* Daniel J Blueman <daniel@xxxxxxxxxxxxx> wrote:

> The Intel SDM [1] and AMD F15h BKDG [2] state that IPIs
> are queued, so the wait_icr_idle() polling is only
> necessary on PPro and older, and maybe then to avoid
> delivery retry. This unnecessarily ties up the IPI
> caller, so we bypass the polling in the Numachip APIC
> driver IPI-to-self path.

It would be nice to propagate this back to the generic x86

> On Linus's earlier point, with the large core counts on
> Numascale systems, I previously implemented a shortcut to
> allow single IPIs to bypass all the cpumask generation
> and walking; it's way down on my list, but I'll see if I
> can generalise and present a patch series at some point
> if interested?

I am definitely interested!


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