Re: disconnect on one usb2.0 port corrupts the communication on the other

[Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>]

On Wed, 17 Oct 2007, Heribert Eilmsteiner wrote:

> Hi
> Today i notices a strange USB hang on my opensuse 10.3 installation.
> 
> "a disconnect on one usb2.0 port corrupts communication on the other"
> 
> How to reproduce:
> 
> 1.	connect 2 memory -sticks
> 2a.	start dd if=<device_stick_1> of=/dev/null
> 2b.	during the transfer, remove stick 2.
> immediately after removal the data transfer to the first
> stick halts
> 
> tried with different linux-versions (2.6.22, 2.6.21 and 2.6.13) and
> different motherboards.
> (intel 855 /845  and AMD based) with  same result.
> on some systems it is necessary to use a usb-cable extender (on the "unplug" stick)
> to reproduce the problem,so i think the reason is an unhandled error in
> the ehci-stack. After enabling USB_DEBUG I noticed an an XActErr in the current transfer
> descriptor.

I was able to duplicate this result on my Intel system.  I plugged a
high-speed hub into the computer and a USB flash disk into the hub, and
a second flash disk into a different port on the same EHCI controller.  
Then I started a "dd" process to read through the contents of the first
flash disk.  When I unplugged the second disk, the transfers to the
first immediately stopped.  Error recovery didn't work; the port was
reset correctly but the Set Address command failed with a -71 error.

Oddly enough, communication with the external hub worked just fine.  
Only the communication with the device plugged into that hub failed.  
This makes you wonder whether the problem lies in the driver or in the 
hub...

> switching the ports to USB 1.1 (through bios or /sys/class/usb_hub/usb_hub/companion)
> avoids the error, but is not satisfying solution.
> 
> Does anyone know of this error and/or of an available fix /patch /workarounds?

No idea what the problem is.  Suggestions are welcome.

Alan Stern


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