Re: [PATCH, RFC] v7 scalable classic RCU implementation

[Manfred Spraul]

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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