Re: Endless loop with "detected XactErr"

From: Alan Stern
Date: Fri Apr 08 2011 - 10:25:24 EST

On Thu, 7 Apr 2011, Zdenek Kabelac wrote:

> Hi
> I've been trying to track some resume error with Intel GPU - and
> notice a couple problems related to resume of my Lenovo T61.
> Laptop has been docked - and suspend/resume has been performed without
> 'undocking' laptop.
> After several iterations of suspend/resume - I've got this endless
> printing loop with this line on console display:
> ehci_hcd 0000:00:1a.7: detected XactErr len 0/4 retry 1
> Just with changing last number - I've got only one such line on serial console.
> By looking into "drivers/usb/host/ehci-q.c" - there seems to be
> endless goto loop.

It isn't endless. You didn't notice the test against QH_XACTERR_MAX.

> From the log it looks like my USB mouse connected to docking station
> was the source of problem.
> (Maybe a movement ??)

This particular error message indicates a hardware problem in the USB
signals. A bad contact, a bad cable, a device failure -- something
like that.

> Here is the trace from last resume:

> [ 473.873802] ACPI: \_SB_.GDCK - undocking
> [ 473.897678] hub 2-0:1.0: state 7 ports 4 chg 0000 evt 0010
> [ 473.904809] ehci_hcd 0000:00:1a.7: detected XactErr len 0/4 retry 1

And presumably additional lines containing similar messages.

There's no real reason for them ever to stop, since they are only
debugging messages. If you turn off CONFIG_USB_DEBUG you'll never see

Alan Stern

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