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xen-devel
Re: [Xen-devel] Re: [PATCH] xen: always handle VIRQ_TIMER first.
>>> On 17.10.10 at 08:11, Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:
> I think (but I haven't spelunked into that code lately) that after a
> tickless idle period it will update jiffies N ticks based on the
> clocksource, and then run any other interrupt handler code, so jiffies
> will always appear to be up to date.
>
> Ah, yes, here it is:
>
> /**
> * tick_nohz_update_jiffies - update jiffies when idle was interrupted
> *
> * Called from interrupt entry when the CPU was idle
> *
> * In case the sched_tick was stopped on this CPU, we have to check if
> jiffies
> * must be updated. Otherwise an interrupt handler could use a stale jiffy
> * value. We do this unconditionally on any cpu, as we don't know whether
> the
> * cpu, which has the update task assigned is in a long sleep.
> */
> static void tick_nohz_update_jiffies(ktime_t now)
> {
> ...
> }
But this is available only with CONFIG_NO_HZ, which is a freely
selectable option. So perhaps the code should still be added
inside an #ifndef CONFIG_NO_HZ?
Jan
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