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From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Subject: Re: [Xen-devel] 4.4: INFO: rcu_sched self-detected stall on CPU
To: Steven Haigh <netwiz@crc.id.au>,
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Cc: "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
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On 03/25/2016 12:04 PM, Steven Haigh wrote:
>
> It may not actually be the full logs. Once the system gets really upset,
> you can't run anything - as such, grabbing anything from dmesg is not
> possible.
>
> The logs provided above is all that gets spat out to the syslog server.
>
> I'll try tinkering with a few things to see if I can get more output -
> but right now, that's all I've been able to achieve. So far, my only
> ideas are to remove the 'quiet' options from the kernel command line -
> but I'm not sure how much that would help.
>
> Suggestions gladly accepted on this front.

You probably want to run connected to guest serial console (" 
serial='pty' " in guest config file and something like 'loglevel=7 
console=tty0 console=ttyS0,38400n8' on guest kernel commandline). And 
start the guest with 'xl create -c <cfg>' or connect later with 'xl 
console <domainID>'.

-boris