Re: [PATCH v5 7/8] mm: Only IPI CPUs to drain local pages if theyexist

[Mel Gorman]

On Tue, Jan 03, 2012 at 12:45:45PM -0500, KOSAKI Motohiro wrote:
> >   void drain_all_pages(void)
> >   {
> > -	on_each_cpu(drain_local_pages, NULL, 1);
> > +	int cpu;
> > +	struct per_cpu_pageset *pcp;
> > +	struct zone *zone;
> > +
> 
> get_online_cpu() ?
> 

Just a separate note;

I'm looking at some mysterious CPU hotplug problems that only happen
under heavy load. My strongest suspicion at the moment that the problem
is related to on_each_cpu() being used without get_online_cpu() but you
cannot simply call get_online_cpu() in this path without causing
deadlock.

If/when I get a patch that can complete a CPU hotplug stress test
successfully, I'll post it. It'll collide with this series but it should
be manageable.

-- 
Mel Gorman
SUSE Labs
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