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). > > (For the following, I am testing with a USB hub, because as I said in a previous > e-mail, I get a kernel panic if I try to plug it in directly to the BeagleBone Black > without the hub. However, I have also had this issue on a BeagleBone Black- > based device running a 3.14.x Yocto-built kernel, where I was able to use it > without a hub, and this issue also occurs when the device is plugged directly > into the BeagleBone Black.) > > If I plug in the rt2800 device, and wait for it to connect to an access point, > then try to disable it by various methods, I get a kernel soft lockup. > > Various methods to disable the device which cause the kernel soft lockup > include (while current directory is e.g. /sys/bus/usb/devices/1-1.3): > > echo 0 > authorized > echo -1 > bConfigurationValue > modprobe -r rt2800usb > echo 1-1.3 > driver/unbind > > On the 4.4.6 kernel, they sometimes succeed, but often cause a soft lockup. > On the 3.14.x Yocto-built kernel, I found they always fail if the Wi-Fi device is > in-use (operating in client or access point mode) but succeed if it is idle. > > E.g. in a recent test doing "echo 0 > authorized", I got the following in the > serial debug console: > > [ 172.167656] NMI watchdog: BUG: soft lockup - CPU#0 stuck for 23s! > [kworker/u2:0:6] [ 200.167589] NMI watchdog: BUG: soft lockup - CPU#0 > stuck for 22s! [kworker/u2:0:6] [ 228.167550] NMI watchdog: BUG: soft > lockup - CPU#0 stuck for 22s! [kworker/u2:0:6] > > In this case, I was able to do a couple of successful "echo 0 > authorized" and > then re-enable with "echo 1 > authorized", before the lockup occurred on a > third "echo 0 > authorized". I'm attaching the corresponding dmesg dump. > My subject previously said "kernel panic" but it's actually a soft lockup. Subject changed. I've also been able to reproduce this on an i586 based eBox-3310A mini PC running Debian 8.4 with a 3.16.0 kernel. On that platform, it does not suffer from the other rt2800 issue I reported (kernel panicwhen connecting to access point without a USB hub), so I was able to test this both with and without a hub. I get a soft lockup in both cases. But in both cases, unplugging the device and/or the hub did not relieve the soft lockup condition. In contrast, I have not been able to reproduce the rt2800 issue of one of my other recent reports (soft lockup on unplug from hub) on the i586 mini-PC platform. -- 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
