The hub sends hot-plug events to the host trough it's interrupt URB. The
driver takes care of completing the URB and re-submitting it. Completion
errors are handled in the hub_event() work, yet submission errors are
ignored, rendering the device unresponsive. All further events are lost.
It is fairly hard to find this issue in the wild, since you have to time
the USB hot-plug event with the URB submission failure. For instance it
could be the system running out of memory or some malfunction in the USB
controller driver. Nevertheless, it's pretty reasonable to think it'll
happen sometime. One can trigger this issue using eBPF's function
override feature (see BCC's inject.py script).
This patch adds a retry routine to the event of a submission error. The
HUB driver will try to re-submit the URB once every second until it's
successful or the HUB is disconnected.
As some USB subsystems already take care of this issue, the
implementation was inspired from usbhid/hid_core.c's.
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Reviewed-by: Oliver Neukum <oneukum@suse.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
8eb58994dd