On 2020-03-18 20:47:18 [-0400], Joel Fernandes wrote:
> In RCU, there are some truly-atomic code sections containing an
> swake_upXX() call, which would be considered atomic also on
> PREEMPT_RT, one example is:
>
> rcu_core() contains an local_irq_{save,restore}() section.
>
> /* No grace period and unregistered callbacks? */
> if (!rcu_gp_in_progress() &&
> rcu_segcblist_is_enabled(&rdp->cblist) && !offloaded) {
> local_irq_save(flags);
> if (!rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL))
> rcu_accelerate_cbs_unlocked(rnp, rdp);
> local_irq_restore(flags);
> }
>
> And rcu_accelerate_cbs_unlocked(rnp, rdp) calls rcu_gp_kthread_wake()
> which does an swake_up_one(), so I think we will have to leave it as
> swake_up() the way it is.
There is also this:
irq_exit()
rcu_irq_exit()
rcu_nmi_exit_common(true);
rcu_prepare_for_idle()
if (rcu_segcblist_pend_cbs(&rdp->cblist))
rcu_gp_kthread_wake()
swake_up_one(&rcu_state.gp_wq);
So I *think* this is another one.
> thanks,
>
> - Joel
Sebastian
