Messages in this thread | | | Date | Tue, 11 Sep 2018 23:45:41 +0800 | From | Ming Lei <> | Subject | Re: [PATCH] percpu-refcount: relax limit on percpu_ref_reinit() |
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On Tue, Sep 11, 2018 at 06:48:36AM -0700, Tejun Heo wrote: > Hello, Ming. > > On Tue, Sep 11, 2018 at 08:00:50AM +0800, Ming Lei wrote: > > > > @@ -357,10 +349,11 @@ EXPORT_SYMBOL_GPL(percpu_ref_kill_and_confirm); > > > > void percpu_ref_reinit(struct percpu_ref *ref) > > > > { > > > > unsigned long flags; > > > > + unsigned long __percpu *percpu_count; > > > > > > > > spin_lock_irqsave(&percpu_ref_switch_lock, flags); > > > > > > > > - WARN_ON_ONCE(!percpu_ref_is_zero(ref)); > > > > + WARN_ON_ONCE(__ref_is_percpu(ref, &percpu_count)); > > > > > > Can you elaborate this part? This doesn't seem required for the > > > described change. Why is it part of the patch? > > > > The motivation of this patch is to avoid the above warning and allow > > the ref to switch back to percpu mode without dropping to zero. > > > > That is why the check has to be changed to the above way. > > So, this part seems wrong. The function is called percpu_ref_reinit() > - the refcnt is expected to be in its initial state with just the base > ref once this function returns. If you're removing the restriction on
But the comment says that 'Re-initialize @ref so that it's in the same state as when it finished', and this invariant isn't changed with this patch.
> when this can be called, you should also make sure that the function > actually enforces the target state. Also, this is a separate logical > change, please put it in a separate patch.
OK, will do it in V2.
Thanks, Ming
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