I previously wrote: > I previously wrote: > > > > I have a D-Link DWA-140 USB Wi-Fi device which is rt2800 based (5392 > > chipset). I've been testing it on a BeagleBone Black running an Ubuntu > > 16.04 image (4.4.6 kernel), with a USB hub. > > > > When I unplug the Wi-Fi device from the USB hub, and it's connected to > > an access point, and then I unplug it, the OS appears to lock up. I > > get messages about a soft lockup on the serial console: > > > > [ 9736.136702] NMI watchdog: BUG: soft lockup - CPU#0 stuck for 22s! > > [kworker/u2:0:1129] [ 9764.136701] NMI watchdog: BUG: soft lockup - > > CPU#0 stuck for 22s! [kworker/u2:0:1129] [ 9792.136701] NMI watchdog: > > BUG: soft lockup - CPU#0 stuck for 22s! [kworker/u2:0:1129] [ > > 9820.136699] NMI > > watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [kworker/u2:0:1129] > > [ 9848.136696] NMI watchdog: BUG: soft lockup - CPU#0 stuck for 22s! > > [kworker/u2:0:1129] > > > > This will repeat indefinitely, until I unplug the hub, which resolves > > the soft lockup and then the system seems to function normally. > > > > I've attached a dmesg log of the soft lockup stack traces. They seem > > to indicate a lockup in workqueue rt2x00usb_work_rxdone() > > (specifically in > > usb_hcd_submit_urb() called from rt2x00usb_kick_rx_entry() called from > > rt2x00usb_clear_entry()). > > > > I originally found this bug on a 3.14.x kernel built with Yocto for a > > BeagleBone Black-based product. So it seems this is a bug that has > > been around for some time. > > I should also note that on the 3.14.x Yocto-built kernel on BeagleBone Black, > this bug does not occur if the rt2800 device is unplugged directly from the > BBB's USB port. It only occurs if unplugged from a hub. > > I have tested this on an i586 based eBox-3310A mini-PC running Debian 8.4, > which has a 3.16.0 kernel, with the same hub and same rt2800 device. But I > was not able to reproduce this issue. There is a patch for the AM335x musb driver that seems to fix this: http://marc.info/?l=linux-usb&m=146173995117456&w=2 So it seems that this issue's root cause is in the AM335x USB interrupt handling, and not the Wi-Fi rt2800 driver. -- Craig McQueen -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
