Re: [PATCH] percpu-refcount: relax limit on percpu_ref_reinit()

Tejun Heo
2018-09-11T16:30:38Z

On Wed, Sep 12, 2018 at 12:05:33AM +0800, Ming Lei wrote:
> On Tue, Sep 11, 2018 at 08:49:59AM -0700, Tejun Heo wrote:
> > On Tue, Sep 11, 2018 at 11:45:41PM +0800, Ming Lei wrote:
> > > > 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.
> >
> > The comment goes "when perpcu_ref_init() finished". The function is
> > called re _init_. It should put the ref in the initial state, right?
>
> OK, I am fine to keep the behaviour for this API, will introduce a new helper
> for NVMe.

Why aren't switch_to_atomic/percpu enough?

> However, it is doable to switch to percpu mode from atomic mode when it
> doesn't drop to zero, looks like sort of perpcu_ref_reinit(inherit_old_refcount).

Isn't that way more contorted than just switching operating modes?

Thanks.

--
tejun