On Thu, 13 Jul 2006 11:50:01 -0700 (PDT)
Linus Torvalds <[email protected]> wrote:
>
>
> On Thu, 13 Jul 2006, Ingo Molnar wrote:
> >
> > +#ifdef CONFIG_LOCKDEP
> > +
> > +/*
> > + * Slab sometimes uses the kmalloc slabs to store the slab headers
> > + * for other slabs "off slab".
> > + * The locking for this is tricky in that it nests within the locks
> > + * of all other slabs in a few places; to deal with this special
> > + * locking we put on-slab caches into a separate lock-class.
> > + */
> > +static struct lock_class_key on_slab_key;
> > +
> > +static inline void init_lock_keys(struct cache_sizes *s)
> > +{
> > + int q;
> > +
> > + for (q = 0; q < MAX_NUMNODES; q++) {
> > + if (!s->cs_cachep->nodelists[q] || OFF_SLAB(s->cs_cachep))
> > + continue;
> > + lockdep_set_class(&s->cs_cachep->nodelists[q]->list_lock,
> > + &on_slab_key);
> > + }
> > +}
> > +
> > +#else
> > +static inline void init_lock_keys(struct cache_sizes *s)
> > +{
> > +}
> > +#endif
>
> Why isn't the "on_slab_key" local to just the init_lock_keys() function,
> and the #ifdef around it all?
>
> Ie just
>
> static inline void init_lock_keys(struct cache_sizes *s)
> {
> #ifdef CONFIG_LOCKDEP
> static struct lock_class_key on_slab_key;
> int q;
>
> for (q = 0; q < MAX_NUMNODES; q++) {
> ...
> #endif CONFIG_LOCKDEP
> }
>
> instead?
>
It could be wholly hidded inside a macro
#define lockdep_go_away(p) {
static struct lock_class_key foo;
lockdep_set_class(p, &foo);
}
But istr suggesting that a couple of weeks ago and was given a
good-sounding reason which I forget.
At least when the code laid out as Ingo proposed, we have room for a
decent comment, which is rather desirable for this sort of thing.
-
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