> I have problems with cdc-acm killing ohci. I tried to narrow down the problem, 
> but didn't get far. 
> Basically `killall -HUP pppd` gives (in dmesg):
> 
> drivers/usb/class/cdc-acm.c: acm_ctrl_irq - urb shutting down with status: -2
> ohci_hcd 0001:01:1b.1: OHCI Unrecoverable Error, disabled
> ohci_hcd 0001:01:1b.1: HC died; cleaning up
> usb 4-1: USB disconnect, address 2
> bus usb: remove device 4-1:1.0
> bus usb: remove device 4-1:1.1
> bus usb: remove device 4-1

After having looked some more hours, it looks like acm_tty_close() unlinks 
urbs too soon or something like that... The attached patch fixes it for me 
(I don't think it's really clean, but it may help ?)

-- 
Colin