Jens Axboe <axboe@xxxxxxxxx> writes:
>
> I mentioned this in our out-of-band discussions on this patch set, and
> we cannot call napi_busy_loop() under rcu_read_lock() if loop_end and
> loop_end_arg is set AND loop_end() doesn't always return true. Because
> otherwise we can end up with napi_busy_loop() doing:
>
> if (unlikely(need_resched())) {
> if (napi_poll)
> busy_poll_stop(napi, have_poll_lock, prefer_busy_poll, budget);
> preempt_enable();
> rcu_read_unlock();
> cond_resched();
> if (loop_end(loop_end_arg, start_time))
> return;
> goto restart;
> }
>
> and hence we're now scheduling with rcu read locking disabled. So we
> need to handle that case appropriately as well.
I'll have a look.
