Found a really fun one.
Plug in or unplug my headphone, and my computer locks up. This is with hda-intel with
msi-enable.
Apparently the headphone plugging/unplugging generates an interrupt. I am using
msi-enable. When the thing sleeps and comes back from sleep, sometimes the kernel, the
BIOS, ACPI, and the snd-hda-intel driver aren't in agreement as to what IRQ the thing
is on. Sometimes I end up with this:
 16:    1321610   IO-APIC-fasteoi   uhci_hcd:usb5, i915@pci:0000:00:02.0, HDA Intel
218:          2      none-edge
219:    3063329      none-edge
I've got RT kernel, and the IRQ-219 is set to highest priority.
 1673 FF      85   - 125  0.2 S<   IRQ-219
 Now, if I am careless enough to generate an interrupt by plugging in the headphone, the
system will lock-up, hard-core.
 I can avoid the problem by whacking the snd-hda-intel driver with a ball-peen hammer
until it decides to go back onto the correct IRQ again:
 sudo modprobe -r snd-hda-intel
 sudo modprobe snd-hda-intel
Yay,
 16:    1337804   IO-APIC-fasteoi   uhci_hcd:usb5, i915@pci:0000:00:02.0
219:    3063459   PCI-MSI-edge      HDA Intel
And no problem.
:-)
-ken