"sudo modprobe -r g_multi" hangs forever.
May 05 13:58:07 beaglebone kernel: INFO: task modprobe:419 blocked for more than 120 seconds.
May 05 13:58:07 beaglebone kernel: Not tainted 4.0.1-bone1 #1
May 05 13:58:07 beaglebone kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
May 05 13:58:07 beaglebone kernel: modprobe D c05f1c79 0 419 418 0x00000001
May 05 13:58:07 beaglebone kernel: [<c05f1c79>] (__schedule) from [<c05f1ea7>] (schedule+0x2f/0x64)
May 05 13:58:07 beaglebone kernel: [<c05f1ea7>] (schedule) from [<bf8951e7>] (gserial_free_port+0x3e/0x94 [u_serial])
May 05 13:58:07 beaglebone kernel: [<bf8951e7>] (gserial_free_port [u_serial]) from [<bf895279>] (gserial_free_line+0x3c/0x64 [u_serial])
May 05 13:58:07 beaglebone kernel: [<bf895279>] (gserial_free_line [u_serial]) from [<bf89c683>] (acm_free_instance+0x12/0x1c [usb_f_acm])
May 05 13:58:07 beaglebone kernel: [<bf89c683>] (acm_free_instance [usb_f_acm]) from [<bf85185f>] (usb_put_function_instance+0x12/0x1c [libcomposite])
May 05 13:58:07 beaglebone kernel: [<bf85185f>] (usb_put_function_instance [libcomposite]) from [<bf88802f>] (multi_unbind+0x2e/0x4c [g_multi])
May 05 13:58:07 beaglebone kernel: [<bf88802f>] (multi_unbind [g_multi]) from [<bf85169b>] (__composite_unbind+0x3e/0x68 [libcomposite])
May 05 13:58:07 beaglebone kernel: [<bf85169b>] (__composite_unbind [libcomposite]) from [<bf8516d3>] (composite_unbind+0xe/0x10 [libcomposite])
May 05 13:58:07 beaglebone kernel: [<bf8516d3>] (composite_unbind [libcomposite]) from [<c047d0d3>] (usb_gadget_remove_driver+0x3f/0x6c)
May 05 13:58:07 beaglebone kernel: [<c047d0d3>] (usb_gadget_remove_driver) from [<c047d149>] (usb_gadget_unregister_driver+0x49/0x7c)
May 05 13:58:07 beaglebone kernel: [<c047d149>] (usb_gadget_unregister_driver) from [<bf8500bb>] (usb_composite_unregister+0xe/0x10 [libcomposite])
May 05 13:58:07 beaglebone kernel: [<bf8500bb>] (usb_composite_unregister [libcomposite]) from [<bf88805b>] (multi_driver_exit+0xe/0x10 [g_multi])
May 05 13:58:07 beaglebone kernel: [<bf88805b>] (multi_driver_exit [g_multi]) from [<c006f617>] (SyS_delete_module+0xdf/0x178)
May 05 13:58:07 beaglebone kernel: [<c006f617>] (SyS_delete_module) from [<c000d6a1>] (ret_fast_syscall+0x1/0x44)