Origin of a kworker-thread

So, after some time I found the solution. In fact Anthon is right, it is the ACPI-subsystem which sends interrupts. On my system I disabled the following interrupts and the kworker-thread is calmed down.

echo disable > /sys/firmware/acpi/interrupts/gpe1B
echo disable > /sys/firmware/acpi/interrupts/gpe08

However until now haven't identified what the bogus IRQs coming from gpe08 and gpe1B.

(Seems to me this is rather off topic here, but here's the answer I posted on unix.stackexchange.com.)

I found this thread on lkml that answers your question a little. (It seems even Linus himself was puzzled as to how to find out the origin of those threads.)

Basically, there are two ways of doing this:

$ echo workqueue:workqueue_queue_work > /sys/kernel/debug/tracing/set_event
$ cat /sys/kernel/debug/tracing/trace_pipe > out.txt
(wait a few secs)

For this you will need ftrace to be compiled in your kernel.

This will output what threads are all doing, and is useful for tracing multiple small jobs.

cat /proc/THE_OFFENDING_KWORKER/stack

This will output the stack of a single thread doing a lot of work. It may allow you to find out what caused this specific thread to hog the CPU (for example). THE_OFFENDING_KWORKER is the pid of the kworker in the process list.