Re: [PATCH 0/2] arm64: Allow the rescheduling IPI to bypass irq_enter/exit

[Peter Zijlstra]

On Mon, Nov 02, 2020 at 10:30:50AM +0000, Valentin Schneider wrote:

> Now, I'd like to pen exactly why we think it's okay to forgo irq_{enter,
> exit}() for that one IRQ and not any other.

Thomas already said a few words on this, but basically scheduler_ipi()
is a NOP (*almost*), the IPI has no body. All it does is tickle the
return-from-interrupt path. So any setup and tear-down done for the
non-existing body is a waste of time.