Comment # 46 on bug 907393 from Dr. Werner Fink

(In reply to Takashi Iwai from comment #45)

Hmmm ... I had added this patch due to a request from the kernel guys. Without
this patch it would not happen but killed after 30 seconds.  Please note that
systemd/udevd uses libkmod.so by spawning a worker process to do the final load
of the module(s).  AFAIK there is no API within libkmod to enable systemd/udevd
to handle success or fail or timeouts (beside of missing dependencies or remove
or insert a not existing module).