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RE: [Xen-devel] State of current Xen debugger

To: "Tim Deegan" <Tim.Deegan@xxxxxxxxxx>
Subject: RE: [Xen-devel] State of current Xen debugger
From: "Roger Cruz" <roger.cruz@xxxxxxxxxxxxxxxxxxx>
Date: Tue, 14 Sep 2010 09:56:27 -0500
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Thread-topic: [Xen-devel] State of current Xen debugger

Hi Tim,  good to hear from you again

I had a pretty good inkling that one of you hardcore developers would say that :-)  Yes, it is pretty well wedged.  I can cause the problem more rapidly by dropping to a single CPU.  When the hang happens, the Xen console is completely dead.  None of the special keys work. 

I do have hopes a BIOS upgrade could fix this as a last resort but I want to see if at least I can understand the problem.  We have a few different machines that are exhibiting similar symptoms so I have to see if I can find a work-around without requiring every user to upgrade their BIOS :-(

Just in case, what debugger have you been using?  Are there recent instructions on how to set it up that you can point me to?


-----Original Message-----
From: Tim Deegan [mailto:Tim.Deegan@xxxxxxxxxx]
Sent: Tue 9/14/2010 10:30 AM
To: Roger Cruz
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-devel] State of current Xen debugger


At 15:22 +0100 on 14 Sep (1284477779), Roger Cruz wrote:
> I am trying to debug a problem where the hypervisor is hanging hard.
> Not even the NMI watchdog is triggering a reboot.  So I wanted to hook
> up a debugger.

Sorry to bring a counsel of despair but if the NMI watchdog isn't
working then your chances of getting a working debugger are slim.  It's
likely that at least one CPU is very very stuck.  Does the 'd' debug key
work on the serial line when the machine is wedged?

On a more cheerful note, I've twice seen hard hangs like this that
turned out to be hardware issues, fixable with BIOS upgrades.



> What is the state of the current debuggers out there?
> Any input on how I should set it up (kdb, gdb, etc) and pointers to a
> good wiki page are much appreciated.  I did perform a Google search
> and found some links but I want to hear from the current developers as
> to what is most stable and useful for debugging this type of hard
> hang.  I only have a serial port PCI-express card to use as the laptop
> has no built in port.

Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, XenServer Engineering
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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