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Date: Tue, 10 Apr 2012 18:00:22 -0700
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
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        "Rafael J. Wysocki" <rjw@sisk.pl>,
        Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
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Subject: Re: CPU Hotplug rework
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On Tue, Apr 10, 2012 at 08:37:18PM -0400, Steven Rostedt wrote:
> On Tue, 2012-04-10 at 17:28 -0700, Paul E. McKenney wrote:
> 
> > > Just to throw out the stupid silly approach.
> > > 
> > > What about creating a "__register_cpu_notifier()" that just does:
> > > 
> > > int __ref __register_cpu_notifier(struct notifier_block *nb)
> > > {
> > > 	return raw_notifier_chain_register(&cpu_chain, nb);
> > > }
> > > 
> > > Also making cpu_maps_update_begin/done() global (and probably rename
> > > them).
> 
> I just noticed that the cpu_maps_update_begin/done() are already global.
> 
> > > 
> > > and then in the above code do:
> > > 
> > > 	cpu_maps_update_begin();
> > > 	__register_cpu_notifier(nb);
> > > 	do_setup();
> > > 	cpu_maps_update_done();
> > > 
> > > 
> > > Just saying,
> > 
> > That does have some attractive properties, now that you mention it.  ;-)
> 
> Which property? Stupid or Silly ;-)

As with any piece of software, no matter how small, both.  ;-)

Of course, __register_cpu_notifier() would need lockdep checking to make
sure that it wasn't called without the benefit of cpu_maps_update_begin().
I might be missing something, but as long as that was in place, seems
like it is a lot simpler and easier to use than the alternatives that
Srivatsa and I were kicking around.

							Thanx, Paul