On Wed, 2013-03-20 at 16:47 +0400, Ilya Zykov wrote: > >> I have little question about flush_to_ldisc(). > >> Does can it be multithreaded? > >> > >> I think yes, because on SMP schedule_work() can work on different CPU paralleled. > > > > Yes, the same work item can now run in parallel on SMP since Tejun Heo > > re-did the workqueue implementation on 2.6.36 [Stefan Richter, the > > firewire maintainer, recently explained this history to me]. > > About multi threaded delayed works: > > In many cases tty layer needs single threaded delayed work for each tty instance. > I propose discussion about create for this purpose (tty layer)'s workqueue with WQ_NON_REENTRANT flag. > And use it instead common schedule_work()'s workqueue - system_wq. > I don't know how expensive(for system resource and CPU) it can be, > but for tty layer, it can be very useful. Ok. I agree it makes sense to explore the possible benefit. There is another potential drawback to using non-reentrant workqueues. The motivation for changing the workqueue api to allow parallel work items on SMP was to fix a class of deadlocks where forward progress could not be made due to subtle dependencies between work items (actually that potential still exists with self-modifying work-items, ie., work items that change their function). The tty layer would need a detailed and thorough analysis of potential dependencies to avoid creating problems. The drivers that use work items might need examination as well. Regards, Peter Hurley -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
