Antonino A. Daplas wrote:
On Fri, 2007-04-27 at 18:08 +0100, James Pearson wrote:
I have a problem whereby the X display 'shifts' to left when anything
writes to /dev/console - where console screen blanking has been disabled
i.e. doing something like:
boot to run level 3
If not root, then make sure /dev/console is writeable
login and type:
setterm -blank 0
start X
type into an xterm:
echo "some random text" > /dev/console
(may have to repeat the echo above a few times)
... and the whole X display jumps (and wraps) to the left
I'm using a RHEL4 based distro with a vanilla 2.6.21 x86_64 kernel
(although I've seen the problem with various x86_64 and i686 2.6.X kernels).
I've seen this problem on a number of different nVidia cards - using
the vesa driver (same problem occurs with nVidia's binary driver). I
haven't tried using other makes of graphics cards.
OK, this may be a strange combination of disabling the text console
blanking and running X, but something isn't right somewhere ...
Yep, it's strange because I can't reproduce this. And the console write
should not succeed if the current console is in KD_GRAPHICS mode, which
is done by X (unless your version is different).
I've just installed a vanilla CentOS 4.4 on an i686 SMP machine - with
an nVidia Quadro4 980 XGL card.
By default, this sets up X using the 'nv' driver (using RedHat's
xorg-x11-6.8.2-1.EL.13.37).
If I follow my 'recipe' above, then the screen shifts - note: it looks
like you have to write several lines of text to /dev/console (at least
30) to trigger the problem (e.g. run the echo to /dev/console in a loop)
- also, I've found that switching to the console and back to X
(Ctrl-Alt-F1 then Ctrl-Alt-F7) while this echo loop is running can force
the shift to start ...
This is with the RedHat based 2.6.9-42.ELsmp kernel - but I also get the
problem with a vanilla 2.6.21 kernel.
Any ideas?
I don't. But, what is your current console? Is it VGA, or framebuffer?
Can you try doing this again in both VGA and vesafb?
I'm not sure what the current console is - whatever is the default with
RHEL4/CentOS4 - how do I select a different type of console?
And this does not happen if there is no previous setterm -blank 0
command?
It doesn't happen if there is no previous 'setterm -blank 0' - so,
arguably, this is the 'fix' ...
James Pearson
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