Re: smp_call_function_single lockups

[Ingo Molnar]

* 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 
code.

> 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!

Thanks,

	Ingo
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