Re: [PATCH v11 2/9] xen: introduce generic non-atomic test_*bit()

["Oleksii K." <oleksii.kurochko@xxxxxxxxx>]

On Tue, 2024-05-28 at 09:53 +0100, Julien Grall wrote:
> > > > +/**
> > > > + * generic_test_bit - Determine whether a bit is set
> > > > + * @nr: bit number to test
> > > > + * @addr: Address to start counting from
> > > > + *
> > > > + * This operation is non-atomic and can be reordered.
> > > > + * If two examples of this operation race, one can appear to
> > > > succeed
> > > > + * but actually fail.  You must protect multiple accesses with
> > > > a
> > > > lock.
> > > > + */
> > > 
> > > You got carried away updating comments - there's no raciness for
> > > simple test_bit(). As is also expressed by its name not having
> > > those
> > > double underscores that the others have.
> > Then it is true for every function in this header. Based on the
> > naming
> > the conclusion can be done if it is atomic/npn-atomic and can/can't
> > be
> > reordered. 
> 
> So let me start with that my only request is to keep the existing 
> comments as you move it. It looks like there were none of test_bit()
> before.
Just to clarify that I understand correctly.

Do we need any comment above functions generic_*()? Based on that they
are implemented in generic way they will be always "non-atomic and can
be reordered.".

Do you find the following comment useful?

" * If two examples of this operation race, one can appear to succeed
 * but actually fail.  You must protect multiple accesses with a lock."

It seems to me that it can dropped as basically "non-atomic and can be
reordered." means that.

~ Oleksii