On Thu, Oct 26, 2023 at 03:00:25PM +0200, Uladzislau Rezki wrote:
> On Wed, Oct 25, 2023 at 05:13:27PM +0200, Frederic Weisbecker wrote:
> > > + llist_for_each_safe(pos, head, head) {
> >
> > Two times head intended here? There should be some
> > temporary storage in the middle.
> >
> Yes. It is intentially done. The head is updated, i.e. shifted to a next,
> because we directly process users from a GP. The number is limited to 5
> all the rest is deferred.
Ah ok.
> > So you can have:
> >
> > * Queue to sr.curr is atomic fully ordered
> > * Check and move from sr.curr to sr.wait is atomic fully ordered
> > * Check from sr.wait can have a quick unatomic unordered
> > llist_empty() check. Then extract unatomic unordered as well.
> > * If too many, move atomic/ordered to sr.done.
> >
> > Am I missing something?
> >
> If too many move to done and kick the helper. The sr.wait can not
> be touched until the rcu_sr_normal_gp_cleanup() is completed, i.e.:
>
> <snip>
> GP-kthread(same and one task context):
> rcu_sr_normal_gp_cleanup();
> wait for a grace period;
> rcu_sr_normal_gp_cleanup();
> <snip>
>
> Am i missing your point?
Yeah got it. My point was just that any manipulation of sr.wait can be
done without atomic/ordered operations. Such as using __list_empty() and
__llist_del_all().
Ah there is also the line:
llist_add_batch(head, tail, &sr.wait);
in rcu_sr_normal_gp_init() that can be turned into __llist_add_batch()
Thanks.
