Re: [PATCH 1/9] percpu-refcount: introduce percpu_ref_is_dead()

[Ming Lei]

On Fri, Sep 01, 2017 at 06:59:15AM -0700, Tejun Heo wrote:
> Hello, Ming.
> 
> > +/**
> > + * percpu_ref_is_dead - test whether a percpu refcount is killed
> > + * @ref: percpu_ref to test
> > + *
> > + * Returns %true if @ref is dead
> > + *
> > + * This function is safe to call as long as @ref is between init and exit.
> > + */
> > +static inline bool percpu_ref_is_dead(struct percpu_ref *ref)
> > +{
> > +   unsigned long __percpu *percpu_count;
> > +
> > +   if (__ref_is_percpu(ref, _count))
> > +   return false;
> > +   return ref->percpu_count_ptr & __PERCPU_REF_DEAD;
> > +}
> 
> Can you please explain why percpu_ref_is_dying() isn't enough for your
> use case?

Hi Tejun,

You are right, looks percpu_ref_is_dying() is enough,
percpu_ref_get_many() works fine no matter the ref is dying or not.

Thanks!

-- 
Ming

Re: [PATCH 1/9] percpu-refcount: introduce percpu_ref_is_dead()

[Bart Van Assche]

On Fri, 2017-09-01 at 06:59 -0700, Tejun Heo wrote:
> > +/**
> > + * percpu_ref_is_dead - test whether a percpu refcount is killed
> > + * @ref: percpu_ref to test
> > + *
> > + * Returns %true if @ref is dead
> > + *
> > + * This function is safe to call as long as @ref is between init and exit.
> > + */
> > +static inline bool percpu_ref_is_dead(struct percpu_ref *ref)
> > +{
> > +   unsigned long __percpu *percpu_count;
> > +
> > +   if (__ref_is_percpu(ref, _count))
> > +   return false;
> > +   return ref->percpu_count_ptr & __PERCPU_REF_DEAD;
> > +}
> 
> Can you please explain why percpu_ref_is_dying() isn't enough for your
> use case?

Hello Tejun,

The approach of the whole series is wrong so I think that you can ignore this 
patch.

Bart.

Re: [PATCH 1/9] percpu-refcount: introduce percpu_ref_is_dead()

[Tejun Heo]

Hello, Ming.

> +/**
> + * percpu_ref_is_dead - test whether a percpu refcount is killed
> + * @ref: percpu_ref to test
> + *
> + * Returns %true if @ref is dead
> + *
> + * This function is safe to call as long as @ref is between init and exit.
> + */
> +static inline bool percpu_ref_is_dead(struct percpu_ref *ref)
> +{
> + unsigned long __percpu *percpu_count;
> +
> + if (__ref_is_percpu(ref, _count))
> + return false;
> + return ref->percpu_count_ptr & __PERCPU_REF_DEAD;
> +}

Can you please explain why percpu_ref_is_dying() isn't enough for your
use case?

Thanks.

-- 
tejun