Hello linux-usb, I think I might have found a kernel bug related to the USB subsystem (cdc_acm perhaps). Context: I was playing around with a device I'm creating, essentially a USB quad modem device that exposes four modems to the host system. This device is still a prototype so there's a few bugs here and there, most likely in the USB descriptors and control requests. What happens: After plugging the device the system starts spitting warnings and BUGs and it locks up. Most of the time some CPUs get into some spinloop and never comes back (you can see it being detected by the watchdog after a few seconds). Generally after that the USB devices stop working completely and at some point the machine freezes completely. In a couple of ocasions I managed to see a bug in dmesg saying "unable to handle page fault for address XXX" and "Supervisor read access in kernel mode" "error code (0x0000) not present page". I could not get a trace for that one since the kernel died completely and my log files were truncated/lost. Since it is happening to my two machines (both Intel but rather different controllers, Sunrise Point-LP USB 3.0 vs 8 Series/C220) and with different kernel versions I suspect this might be a bug in the kernel. I have 4 logs that I collected, they are sort of long-ish, not sure how to best send them to the list. Thanks! David
