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[Xen-devel] Re: xen hg tree from yesterda hangs when kernel console is directed to ttyS0

This may not be new with the latest source. I've been seeing the same
thing for some time, on certain hardware. It's right after boot,
generally while printing the E820 map.  I've noticed some patterns
to it, but haven't spent the time to track it down. There's always
been something else more pressing to do.  One slight difference is
between your example and what I've been doing is that I only use
com1 as the console for Xen.  I've never seen it hang with only
vga as the console, but only with com1.

And, while it may seem unlikely that a simple serial UART is
having problems, it's quite possible.


Date: Mon, 20 Mar 2006 11:04:05 +0000
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] Re: [Xen-users] xen hg tree from yesterday
        hangs,  when kernel console is directed to ttyS0

On 19 Mar 2006, at 15:10, Jussi Hamalainen wrote:

>>>> When I reboot my system with xen with the following options to xen
>>>> and vmlinuz,
>>>> xen.gz com1=115200,8n1 console=com1,vga
>>>> vmlinuz console=ttyS0,115200 console=tty0
>>>> the system hangs up while booting the dom0 kernel.
>> I think Xen has a major buffering/blocking IO issue with serial
>> console. It works for a while but when loads of lines get
>> flooded onto the console, the system freezes up. Adding a
>> "sync_console" to your Xen parameters might solve the problem, or at
>> least it worked for me.

Maybe it's hardware specific. I can echo a long string to the serial
console in a tight loop from dom0 shell and I see no problems. My setup
is similar to the OP's (115200 baud).

  -- Keir

Ben Thomas                                         Virtual Iron Software
bthomas@xxxxxxxxxxxxxxx                            Tower 1, Floor 2
978-849-1214                                       900 Chelmsford Street
                                                   Lowell, MA 01851

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