On Thu, May 12, 2022 at 04:56:03PM -0700, Paul E. McKenney wrote:
> On Thu, May 12, 2022 at 03:04:29AM +0000, Joel Fernandes (Google) wrote:
> > + preempt_enable();
> > +
> > + if (debug_rcu_head_queue((void *)head)) {
> > + // Probable double call_rcu(), just leak.
> > + WARN_ONCE(1, "%s(): Double-freed call. rcu_head %p\n",
> > + __func__, head);
> > +
> > + // Mark as success and leave.
> > + return;
> > + }
> > +
> > + // Queue to per-cpu llist
> > + head->func = func;
> > + llist_add(&head->llist_node, &rlp->head);
>
> Suppose that there are a bunch of preemptions between the preempt_enable()
> above and this point, so that the current CPU's list has lots of
> callbacks, but zero ->count. Can that cause a problem?
>
> In the past, this sort of thing has been an issue for rcu_barrier()
> and friends.
Speaking of, shouldn't rcu_barrier() flush all the lazy queues? I
might have missed that somewhere in the patchset though.
Thanks.
