* Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> > And if we are into getting reference counts, why not solve it at a higher
> > level and get a reference count to 'x' to make sure it's safe to use? Then we
> > could do:
> >
> > lock(y->lock);
> > retry:
> > x = y->x;
> > if (!trylock(x->lock)) {
> > get_ref(x->count)
> > unlock(y->lock);
> > lock(x->lock);
> > lock(y->lock);
> > put_ref(x->count);
> > if (y->x != x) { /* Retry if 'x' got dropped meanwhile */
> > unlock(x->lock);
> > goto retry;
> > }
> > }
> >
> > Or so.
>
> In the case of dcache::dentry_kill() we probably do not have to take refcounts
> and it might be actually counterproductive to do so. y->x, i.e. dentry->parent,
> cannot vanish under us, if I understand the life time rules correctly.
Ok, that's even better.
> Aside of that, yes, I was thinking about a similar scheme for that. I need some
> more time to grok all the rules there :)
Ok, great! :-)
I really don't think we need a new locking primitive - and with something like the
above we could improve the code upstream as well and make it scale better in some
scenarios, right?
Thanks,
Ingo
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