On Fri, 3 Oct 2008, Dave Hansen wrote:

quoted text
> I'm seeing some odd USB behavior with newer kernels
> (2.6.27-rc8-00062-g330f647 to be exact).  Almost exactly, every 30
> seconds, one of my USB hubs disconnects.

Actually two of the hubs disconnect: 3-4.1 and 3-4.4.4.  Neither is 
beneath the other.

quoted text
>  At first, I thought it was a
> hardware issue, and started swapping cables.  Then, I realized that I'd
> *just* rebooted into a new kernel.  So, I booted back to the distro
> kernel and these went away.
> 
> Even though my mouse is hanging off that hub,

No it isn't.  The mouse is 3-4.4.1, which is not below either 3-4.1 or 
3-4.4.4.

quoted text
> I don't seem to notice the
> disconnects.
> 
> $ dmesg | grep disconnect
> [ 3599.496217] usb 3-4.4.4: USB disconnect, address 122
> [ 3599.677346] usb 3-4.1: USB disconnect, address 121
> [ 3627.804621] usb 3-4.1: USB disconnect, address 124
> [ 3628.004400] usb 3-4.4.4: USB disconnect, address 123
> [ 3659.496421] usb 3-4.4.4: USB disconnect, address 126
> [ 3659.676186] usb 3-4.1: USB disconnect, address 125
> [ 3689.493763] usb 3-4.1: USB disconnect, address 3
> [ 3689.708916] usb 3-4.4.4: USB disconnect, address 127
> [ 3719.497221] usb 3-4.4.4: USB disconnect, address 7
> [ 3719.684965] usb 3-4.1: USB disconnect, address 6
> [ 3749.496323] usb 3-4.1: USB disconnect, address 9
> [ 3749.691180] usb 3-4.4.4: USB disconnect, address 8
> 
> Full dmesg and .config:
> 
> http://sr71.net/~dave/linux/config-10-03-2008.1.txt
> http://sr71.net/~dave/linux/dmesg-10-03-2008.1.log
> 
> The last one I tried before this was -rc3, and it appears to be OK.  The
> Ubuntu 2.6.24-19-generic kernel also appears not to have this issue.
> 
> A quick scan of LKML and linux-usb didn't turn up anything similar.
> 
> The machine is a Lenovo T61 plugged into the Lenovo dock.  At this
> point, the only thing plugged into the suspect hub is my mouse.

In fact, nothing is plugged into either of the hubs.

In theory this could be caused by a problem in the dock.  But it would 
be better to get more information before trying to pin down the cause.

You should use usbmon (see Documentation/usb/usbmon.txt) to record a 
trace of everything happening on bus 3.  And to keep things simple, you 
should unplug all the USB devices except for one of the magical 
disappearing hubs.

Alan Stern

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