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SubjectRe: [PATCH, RFC] v7 scalable classic RCU implementation
Paul E. McKenney wrote:
>> How do you intend to handle nohz cpus?
>>
>
> In which variant of RCU? My current thought is to apply the rcutree.c
> version to rcupreempt.c. If rcuclassic.c can be dropped, my thought
> would be to leave it alone -- it is unnecessarily awakening CPUs, but
> this is a non-fatal issue.
>
>
For rcuclassic.

As far as I can see, rcuclassic treats nohz cpus as always outside
rcu_read_lock():
rcu_start_batch() contains
>
> cpus_andnot(rcp->cpumask, cpu_online_map, nohz_cpu_mask);
>
As soon as all cpus from rcp->cpumask reported a grace period, the
callbacks are called.
That a bug, therefore I would drop rcuclassic as soon as rcutree is merged.

--
Manfred



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