Re: [Xen-devel] Regression in serial console on ia64

[Horms <horms@xxxxxxxxxxxx>]

On Tue, Sep 11, 2007 at 02:55:47PM +0200, Markus Armbruster wrote:
> Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> writes:
> 
> > On 11/9/07 12:12, "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx> wrote:
> >
> >> On 11/9/07 12:06, "Horms" <horms@xxxxxxxxxxxx> wrote:
> >> 
> >>> I havnen't investigated why, but 52f308b17bae
> >>> "xencons: Remove xencons_early_setup() and do not clear use_vt_console."
> >>> seems to cause a regression on ia64.
> >>> 
> >>> The problem is that with this change applied the console
> >>> seems to stop just before the end of boot - no more output,
> >>> no input.
> >> 
> >> Is this when booting dom0? And its serial output (via Xen) that is 
> >> affected?
> >> Do you have console=xvc0 on your dom0 cmdline (and no other console= 
> >> lines)?
> >
> > My guess is that you have console=tty0 on your cmdline and this is taking
> > precedence over your serial console for init output. I've seen this kind of
> > issue before on native when trying to have both console=tty0 and
> > console=ttyS0 on the cmdline -- init output always seems to go to only one
> > or the other. I think it's supposed to be the case that the *last* console=
> > on your cmdline is the one that gets /dev/console and thus gets to swallow
> > init's output. I'm not sure what the fix is (if any) if you really want your
> > init output to go to multiple console sinks.
> 
> Kernel messages (printk) go to all registered consoles with flag
> CON_ENABLED.
> 
> User space talks to /dev/console.  The kernel routes that to the
> preferred console, which is the last one on the command line, if any,
> or else the first one to register (typically the virtual terminal).

Hi,

Thanks for the help.

Previously I had console=tty0 console=ttyS0, which used to work fine
but now doesn't. Though perhaps it shouldn't have worked at all.

I now have console=ttyS0 only, and everything is working fine.

I am guessing that with dual consoles, printk is going to both consoles,
but user-space only goes to the first console, as Markus suggests. And I
guess that for some reason previously user-space also went to both
consoles.

I also tried with console=ttyS0 console=tty0, and both printk and
in this case user-space does not seem to go to the serial console,
perhaps tty0 always wins for some reason?

Thanks again.

-- 
Horms
  H: http://www.vergenet.net/~horms/
  W: http://www.valinux.co.jp/en/


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