Re: [PATCH v5 06/13] lockdep: Implement crossrelease feature

Byungchul Park
2017-02-28T14:10:06Z

On Tue, Feb 28, 2017 at 02:10:12PM +0100, Peter Zijlstra wrote:
> > +#ifdef CONFIG_LOCKDEP_CROSSRELEASE
> > +
> > +#define idx(t) ((t)->xhlock_idx)
> > +#define idx_prev(i) ((i) ? (i) - 1 : MAX_XHLOCKS_NR - 1)
> > +#define idx_next(i) (((i) + 1) % MAX_XHLOCKS_NR)
>
> Note that:
>
> #define idx_prev(i) (((i) - 1) % MAX_XHLOCKS_NR)
> #define idx_next(i) (((i) + 1) % MAX_XHLOCKS_NR)
>
> is more symmetric and easier to understand.

OK. I will do it after forcing MAX_XHLOCKS_NR to be power of 2. Current
value of it is already power of 2 but I need to add comment explaning it.

> > +
> > +/* For easy access to xhlock */
> > +#define xhlock(t, i) ((t)->xhlocks + (i))
> > +#define xhlock_prev(t, l) xhlock(t, idx_prev((l) - (t)->xhlocks))
> > +#define xhlock_curr(t) xhlock(t, idx(t))
>
> So these result in an xhlock pointer
>
> > +#define xhlock_incr(t) ({idx(t) = idx_next(idx(t));})
>
> This does not; which is confusing seeing how they share the same
> namespace; also incr is weird.

OK.. Could you suggest a better name? xhlock_adv()? advance_xhlock()?
And.. replace it with a function?