On Mon, 2018-09-24 at 11:01 -0700, Tejun Heo wrote: > Hello, Bart. > > On Fri, Sep 21, 2018 at 01:31:19PM -0700, Bart Van Assche wrote: > > +void percpu_ref_resurrect(struct percpu_ref *ref) > > +{ > > + unsigned long __percpu *percpu_count; > > unsigned long flags; > > > > spin_lock_irqsave(&percpu_ref_switch_lock, flags); > > > > - WARN_ON_ONCE(!percpu_ref_is_zero(ref)); > > + WARN_ON_ONCE(!(ref->percpu_count_ptr & __PERCPU_REF_DEAD)); > > + WARN_ON_ONCE(__ref_is_percpu(ref, &percpu_count)); > > So, this in itself is fine but I'm a bit worried that this might it > easier to abuse percpu_ref's dying mode. More specifically, it isn't > a good idea to depend on percpu_ref's implementation details from > outside - ie. the only guarantee there ever is that percpu_ref won't > give out new refs after ->percpu_ref is called - e.g. users can't > piggy back on implied rcu grace period. > > Can you please note that in the function comment? Provided that, > > Acked-by: Tejun Heo <t...@kernel.org>
Hi Tejun, Thanks for the review. But could you please clarify what "after ->percpu_ref is called" refers to? Thanks, Bart.