Re: [PATCH] hotplug: Optimize {get,put}_online_cpus()

[Paul E. McKenney]

On Tue, Oct 01, 2013 at 04:48:20PM +0200, Peter Zijlstra wrote:
> On Tue, Oct 01, 2013 at 07:45:37AM -0700, Paul E. McKenney wrote:
> > If you don't have cpuhp_seq, you need some other way to avoid
> > counter overflow.  Which might be provided by limited number of
> > tasks, or, on 64-bit systems, 64-bit counters.
> 
> How so? PID space is basically limited to 30 bits, so how could we
> overflow a 32bit reference counter?

Nesting.

							Thanx, Paul

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