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);
}
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.
