Unfair qspinlocks on ARM64 without LSE atomics => 3ms delay in interrupt handling

[Bouska, Zdenek]

> Why is this interrupt handling specific? Just because it's the place
> where you observed it?
Yes.

> So if that helps, then this needs to be addressed globaly and not with
> some crude hack in the interrupt handling code.
I just wrote, what helps for me. I didn't mean it as a proposal for merge.
Sorry for confusion.

I tried using Will's cpu_relax() implementation [1] everywhere but I was not 
successful with that yet. ARM64's VDSO makes it complicating and even
if I left original cpu_relax() just in VDSO, Linux did not boot for me.

Thank you all!

[1] https://lore.kernel.org/lkml/20170728092831.GA24839@arm.com/

Zdenek Bouska

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