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SubjectRe: [RFC/RFT PATCH 1/2] sched/core: Check and schedule ksoftirq
On Fri, Dec 16, 2022 at 12:19:34PM +0100, Peter Zijlstra wrote:
> On Thu, Dec 15, 2022 at 10:42:59AM -0800, Srinivas Pandruvada wrote:
> > + /* Give ksoftirqd 1 jiffy to get a chance to start its job */
> > + if (!READ_ONCE(it.done) && task_is_running(__this_cpu_read(ksoftirqd))) {
> > + __set_current_state(TASK_UNINTERRUPTIBLE);
> > + schedule_timeout(1);
> > + }
>
> That's absolutely disgusting :-/

I know, and I hate checking task_is_running(__this_cpu_read(ksoftirqd))
everywhere in idle. And in fact it doesn't work because some cpuidle drivers
also do need_resched() checks.

I guess that either we assume that the idle injection is more important
than serving softirqs and we shutdown the warnings accordingly, or we arrange
for idle injection to have a lower prio than ksoftirqd.

Thoughts?

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