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SubjectRe: 'global' rq->clock
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> on nohz we still keep jiffies uptodate - despite there not being an
> explicit 'keep jiffies uptodate' tick interrupt anymore. So on every
> irq_enter() we roll jiffies forward - if needed - and thus emulate
> jiffies behavior to drivers and core kernel code, etc.
>
> if an IPI on Power does not do an irq_enter() then you might miss out on
> updated jiffies. That might not matter for most jiffies, but you might
> also miss out on the 'touch the softlockup watchdog because we just woke
> from idle' action. This is what triggered the false positive warnings on
> Sparc64.
>
> the same bug existed on x86 too: that too does a few IPIs without
> irq_enter/irq_exit. We now removed the softlockup dependency so it
> should not be required to do an irq_enter()/exit anymore - unless the
> code that the IPI uses accesses jiffies. (but that would be unusual)

Allright, so it looks like we don't have a problem today, though I'll be
careful if some of our CPUs come up with more fancy ways to do IPIs.
Currently they are just normal interrupts, so we do irq_enter/exit and
we process softirqs on the way out.

Ben.




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