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SubjectRe: [RFC] sched: Add a new lockless wake-from-idle implementation

* Andy Lutomirski <> wrote:

> This is a strawman proposal to simplify the idle implementation, eliminate
> a race
> Benefits over current code:
> - ttwu_queue_remote doesn't use an IPI unless needed


> - The diffstat should speak for itself :)


> - Less racy. Spurious IPIs are possible, but only in narrow windows or
> when two wakeups occur in rapid succession.
> - Seems to work (?)
> Issues:
> - Am I doing the percpu stuff right?
> - Needs work on non-x86 architectures

Absolutely, and with the least amount of disruption possible, as
people are not very good at testing 'all' of them.

> - The !CONFIG_SMP case needs to be checked

Which also happens to be the default for half of all non-x86 arches.

> - Is "idlepoll" a good name for the new code? It doesn't have *that*
> much to do with the idle state. Maybe cpukick?

'cpukick', hands down.

> If this turns out okay, TIF_NEED_RESCHED could possibly be deleted as well.

Cool ...



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