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SubjectRe: [RFC] sched,livepatch: call klp_try_switch_task in __cond_resched
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On Tue, 2022-05-10 at 09:52 -0700, Josh Poimboeuf wrote:
> On Tue, May 10, 2022 at 04:07:42PM +0000, Rik van Riel wrote:
> > >
> > Now I wonder if we could just hook up a preempt notifier
> > for kernel live patches. All the distro kernels already
> > need the preempt notifier for KVM, anyway...
> >
>
> I wouldn't be opposed to that, but how does it solve this problem? 
> If
> as Peter said cond_resched() can be a NOP, then preemption would have
> to
> be from an interrupt, in which case frame pointers aren't reliable.
>
The systems where we are seeing problems do not, as far
as I know, throw softlockup errors, so the kworker
threads that fail to transition to the new KLP version
are sleeping and getting scheduled out at times.

A KLP transition preempt notifier would help those
kernel threads transition to the new KLP version at
any time they reschedule.

How much it will help is hard to predict, but I should
be able to get results from a fairly large sample size
of systems within a few weeks :)
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