Hello, Kent.
On Mon, Jan 28, 2013 at 12:55:40PM -0800, Kent Overstreet wrote:
> > I don't understand why we need two stages. What prevents the killing
> > thread from fetching percpu counters after dying passes one
> > synchronize_sched()?
>
> It does. The second synchronize_sched() is needed after we set state :=
> dead, and before we drop the initial ref. Otherwise the ref could hit 0
> before percpu_ref_put knows to check for it.
Still a bit confused. Why do we need to make the two steps separate?
What prevents us from doing the following?
set dying;
synchronize_sched();
collect percpu refs into global atomic_t;
put the base ref;
Thanks.
--
tejun
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