[ale] checking for process in uninterruptable sleep state

[Todor Fassl]

[Sorry to top post but I am blind and it is very difficult for me to 
post in-line.]

These workstations are in a lab and students  are plugging usb devices 
into them all the time. I was checking the logs on one machine last week 
and I saw that somebody had plugged a web cam in. I am guessing it was 
for skype and/or linphone. I will never be able to pin it down to a 
specific usb device.

But every time a machine is hung, it is always that same file, 
/sys/bus/usb/devices/usb1/descriptors, that causes it to go into an 
uninterruptable sleep. So I think the defective usb device is the usb 
controller itself.

Well, I set the kernel parameter to disable usb autosuspend. I'll post 
back if it works. I did manage to write a script to notifiy me when the 
problem occurs so if the script doesn't trigger in a couple of days, I'm 
going to say it's fixed.





On 05/10/2016 10:16 AM, Phil Turmel wrote:
> On 05/10/2016 10:39 AM, Todor Fassl wrote:
>> Details: I have 15 Dell workstations running ubuntu 15.10 (2 are running
>> 16.04 -- that did not help). Occasionally, the keyboard and mouse
>> freeze. Logging in remotely and running lsusb hangs such that you can't
>> even control-c outand it cannot be killed even with a -9. The process
>> goes into an uninterruptable sleep during a system call to open the file
>> /sys/bus/usb/devices/usb1/descriptors. That file is part of the kernel's
>> control files for the usb controller itself. So you can see why the
>> keyboard and mouse are dead, the driver for the usb controller itself is
>> hung.
>
>> PS: I wouldn't mind ideas wrt the original problem either. Not that I
>> hold out any hope for that.
>
> Ah, you have buggy USB devices.  I've run into this.  I used the kernel
> boot parameter usbcore.autosuspend=-1 to globally disable USB per-device
> power saving on my mythtv server.  If you can narrow it down to a
> specific set of devices, you could create udev rules to prevent just
> those from sleeping.
>
> Some links:
>
> http://unix.stackexchange.com/questions/91027/how-to-disable-usb-autosuspend-on-kernel-3-7-10-or-above
>
> http://askubuntu.com/questions/80638/how-to-disable-auto-power-off-of-usb-devices-like-usb-mouse
>
> Phil
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-- 
Todd