udev-rtirq automatically changes the priority of soundcard interrupt handling threads.
Linux low-latency audio depends on the concept of POSIX realtime threads, the idea being to run important audio processing as realtime threads at a high priority, thus giving the work preference to much anything else running on the system.
udev-rtirq automatically changes the priority of the thread handling the soundcard, firewire or usb hub interrupt when it detects that a soundcard has been added or removed.
udev-rtirq accomplishes this by installing an udev rule which calls a script to find the thread handling the interrupt and then changing its priority to a predefined value.
udev-rtirq needs interrupt handlers exported as threads to userspace, this can be achieved either by using a realtime kernel, or booting a lowlatency kernel with the "threadirqs" boot flag.
In its present form it also depends on systemd.
Run make install to copy the udev rules file, the script, and the default config file to the right destinations.
By default udev-rtirq will set the interrupt handler to priority 95 when it detects a soundcard, and it will set it back to 50 when it detects its removal. You can change the priority level in /etc/defaults/udev-rtirq. You can also blacklist certain PCI ids, say you have a soundcard for which you'd never want to change the priority.