>
> Le Mon, Oct 21, 2024 at 07:01:02PM +0800, Z qiang a écrit :
> > > For the non-nocb cpus set during boot, the corresponding
> > > rcuop kthread, we should park directly, otherwise
> > > WARN_ON_ONCE(!rcu_rdp_is_offloaded(rdp)) will be triggered.
>
> Ah but this case is different. kthread_park() is called on
> the kthread that is freshly created. In that case it is
> parked before the kthread even had a chance to call its handler
> (which is rcu_nocb_cb_kthread()).
>
> See these lines in kthread():
>
> /* OK, tell user we're spawned, wait for stop or wakeup */
> __set_current_state(TASK_UNINTERRUPTIBLE);
> create->result = current;
> /*
> * Thread is going to call schedule(), do not preempt it,
> * or the creator may spend more time in wait_task_inactive().
> */
> preempt_disable();
> complete(done);
> schedule_preempt_disabled();
> preempt_enable();
>
> ret = -EINTR;
> if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) {
> cgroup_kthread_ready();
> __kthread_parkme(self);
> ret = threadfn(data);
> }
>
Ah, Thanks!
get it, I ignored parkme in kthread(),
will update and resend.
Thanks
Zqiang
>
>
> So really rcu_rdp_is_offloaded() has to be true (but we can
> warn if it's not. Though we already have a test for this in
> nocb_cb_wait()).
>
> Thanks.
