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SubjectRe: [RFC:Patch: 000/008](memory hotplug) rough idea of pgdat removing
> Yasunori Goto wrote:
>
> > I thought it at first, but are there the following worst case?
> >
> >
> > CPU 0 CPU 1
> > -------------------------------------------------------
> > __alloc_pages()
> >
> > parsing_zonelist()
> > :
> > enter page_reclarim()
> > sleep (and remember zone) :
> > :
> > update zonelist and node_online_map
> > with stop_machine_run()
> > free pgdat().
> > remove the Node electrically.
> >
> > wake up and touch remembered
> > zone, but it is removed
> > (Oops!!!)
> >
> >
> >
> > Anyway, I'm happy if there is better way than my poor idea. :-)
> >
> > Thanks for your comment.
>
> Duh. Then the use of RCU would also mean that all of reclaim must
> be in a rcu period. So reclaim cannot sleep anymore.

I use srcu_read_lock() (sleepable rcu lock) if kernel must be sleep for
page reclaim. So, my patch basic idea is followings.


CPU 0 CPU 1
-------------------------------------------------------
__alloc_pages()

rcu_read_lock() and check
online bitmap
parsing_zonelist()
rcu_read_unlock()
:
enter page_reclarim()
srcu_read_lock()
parse zone/zonelist.
sleep (and remember zone) :
:
update zonelist and node_online_map
with stop_machine_run()

wake up and touch remembered zone,
srcu_read_unlock()
syncronized_sched().
free_pgdat()


Thanks.

--
Yasunori Goto




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