Actually, I never send reschedule IPIs.
- For "usual" cpus, rcu_check_callbacks() checks for quiescent states.
There should be a set_need_resched() if a cpu holds up a grace period
for too long. I just haven't implemented it yet.
IMHO it doesn't make sense to perform a "for_each_cpu()
smd_send_reschedule()". rcu has a hook in each cpu, thus a
set_need_resched() by the per-cpu hook is faster/simpler.
- For nohz cpus, a poller function [schedule_work(), enabled interrupts]
peeks into the per-cpu data of the nohz cpu and checks if it is quiet or
if it passed through a quiescent state.
If it didn't, then it sets a cpu_data->kick_poller flag and
rcu_irq_exit() reports the grace period.
No need for an IPI either - rcu has a hook in the irq exit path.
Right now, I cheat if a nohz cpu is in a long-running nmi
[while(other_cpu_is_in_nmi()) cpu_relax()], but I think I can fix that
with an set_need_resched() in the rcu_nmi_exit().
--
Manfred
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