Le Mon, Nov 11, 2024 at 01:07:16PM +0530, Neeraj Upadhyay a écrit :
>
> > diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
> > index 16865475120b..2605dd234a13 100644
> > --- a/kernel/rcu/tree_nocb.h
> > +++ b/kernel/rcu/tree_nocb.h
> > @@ -891,7 +891,18 @@ static void nocb_cb_wait(struct rcu_data *rdp)
> > swait_event_interruptible_exclusive(rdp->nocb_cb_wq,
> > nocb_cb_wait_cond(rdp));
> > if (kthread_should_park()) {
> > - kthread_parkme();
> > + /*
> > + * kthread_park() must be preceded by an rcu_barrier().
> > + * But yet another rcu_barrier() might have sneaked in between
> > + * the barrier callback execution and the callbacks counter
> > + * decrement.
> > + */
> > + if (rdp->nocb_cb_sleep) {
>
> Is READ_ONCE() not required here?
No because it can't be written concurrently at this point. The value observed
here if kthread_should_park() must have been written locally on the previous
call to nocb_cb_wait().
Thanks.
>
>
> - Neeraj
>
> > + rcu_nocb_lock_irqsave(rdp, flags);
> > + WARN_ON_ONCE(rcu_segcblist_n_cbs(&rdp->cblist));
> > + rcu_nocb_unlock_irqrestore(rdp, flags);
> > + kthread_parkme();
> > + }
> > } else if (READ_ONCE(rdp->nocb_cb_sleep)) {
> > WARN_ON(signal_pending(current));
> > trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WokeEmpty"));
>
