Sorry for taking my time replying. Really appreciate you answering!

Is the workqueue usage that is problematic in the tty core?  Or, is it
in a specific driver?  This is a more generic problem with most of the
deferred work mechanisms that the kernel offers.

Any work deferral system that doesn't map work units one-to-one with
threads suffers the problem where the units cannot independently be
prioritized amongst other system tasks.

It's in the tty core. Some work queue usage in the driver also, but it seems to only be at open or close.

Everyone always asks "is there a kernel config option that magically
fixes my problem?", and the answer is almost always "no" :).

Without having more information about the case you are looking at, I
think it will be difficult to prescribe a potential solution.  If the
workqueue is being used to defer work from interrupt context, then the
use of request_threaded_irq() and pushing the work to thread context
would be better.

I see. Hm, there is some IRQ thread, but not exactly sure if it's the kind you mean, or just a smaller handler. Luckily, we found a patch that converts tty core to using its own kthreads (http://www.spinics.net/lists/linux-serial/msg17783.html). Looking into it right now. It does seem promising.

Regards,
Rasmus Ahlberg
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