Jan Kara wrote: > > So for UP systems, we should by default disable async printing anyway I > > suppose. It is just a pointless overhead. So please just make printk_sync > > default to true if !CONFIG_SMP. > > > > When IRQs are disabled, you're right we will have a change in behavior. I > > don't see an easy way of avoiding delaying of printk until IRQs get > > enabled. I don't want to queue work directly because that creates > > possibility for lock recursion in queue_work(). And playing some tricks > > with irq_works isn't easy either - you cannot actually rely on any other > > CPU doing anything (even a timer tick) because of NOHZ. > > > > So if this will be a problem in practice, using a kthread will probably be > > the easiest solution. > > Hum, and thinking more about it: Considering that WQ_MEM_RECLAIM workqueues > create kthread anyway as a rescuer thread, it may be the simplest to just > go back to using a single kthread for printing. What do you think? >
I think a plain kthread is better. printing_work_func() can become a buggy function. console_unlock() from printing_work_func() can occupy kworker for many seconds due to looping with cond_resched() (i.e. without calling schedule_timeout_*()) from schedulable context which can in turn defer other work items.
