quoted

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.

quoted

What do you think about this race condition?
https://lkml.org/lkml/2011/11/7/98

Yes, that is a possible race condition that could lead to some nasty
results. Good find.

If you want, I could bring that patch into this patchset or you could
re-submit that patch to Greg and I could rebase this patchset on top of
that.

Peter,
Please, do it anywhere you consider possible,
I can't do it myself now.

Thank you,
Ilya.