Re: [PATCH] kernel/printk.c: Concerns about the console handover

Russell King
2007-09-21T13:10:39Z

On Fri, Sep 21, 2007 at 02:42:34PM +0200, Gerd Hoffmann wrote:
> Andrew Morton wrote:
> > On Thu, 20 Sep 2007 18:28:49 +0100 (BST) "Maciej W. Rozycki" <macro@linux-mips.org> wrote:
> >
> >> Move the hadover message to after the boot console has been released to
> >> avoid bad interactions between it and the real console.
>
> [ longish problem discussion snipped ]
>
> >> considered fully disabled. Below is a change which makes the problem
> >> disappear for me, but I suppose there was a deliberate reason for placing
> >> the printk() where it is now and nowhere else.
>
> Well, I placed the printk there is for user interface reasons. I think
> especially in case the early console and the real console go to
> different physical devices it is useful to have the reason it stops
> printing messages displayed on the early console. So people don't think
> the computer hangs although it just prints messages elsewhere ...
>
> If that isn't going to work due to two instances not knowing each other
> (kernel & firmware) should not mess with the same physical device, then
> I'd just drop the printk. And I see no pretty and easy way around that
> issue :-(
>
> We could do the printk and unregister before we setup the new console.
> Which has the drawback that we are in trouble in case the setup() call
> for the new console fails ...
>
> We could split the printk into two, one early ("trying to setup new
> console foo") which goes to the boot console, then (assuming the setup
> worked ok) unregister silently and print a message about the successful
> init and boot console unregister on the new console only. Which results
> in two lines being printed for the handover when both consoles address
> the same physical device. Not that nice IMHO, but maybe still the best
> way to handle it.

I had an issue with the console initialisation on serial ports, which I
discovered during my PXA work. My reason for asking about the kernel
versions (which Andrew forwarded to LKML) is to determine whether the
report is as a result of those changes, or lack of those changes.

Those -mm versions with git-arm in probably have that change. Ergo
the importance to answer this question about kernel versions.

--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/