[multiseat] hard freeze when running "X -arguments... :1"

[Tomasz Chmielewski]

I'm trying to write some easy to follow documentation about setting up 
a multiseat workstation.

So far I have one problem: my computer freezes whenever I want to use 
GDM as a desktop manager. On the other hand, everything works fine if 
I use KDM.

Closer investigation turned up that the freeze does not really depend 
on the desktop manager, but on the order X servers are started.

For example, if I boot the PC to the console, then start:

/usr/bin/Xorg -nolisten tcp -layout seat1 -sharevts -novtswitch -isolateDevice PCI:2:5:0 :1

The computer hard freezes. What's interesting, I can see a few first 
lines of the X server output and a blinking cursor, but that's about it.
There is nothing in the logs (even when the filesystem is mounted with 
"sync" option"), machine doesn't reboot even if I pass the kernel panic=10
parameter (so it's not a kernel panic), there is no reaction for key presses
(caps lock, ctrl+alt+del, ctrl+alt+backspace, sysrq+s, sysrq+b, sysrq+o etc.),
machine doesn't send any packets any more (i.e., ping to another machine
started from a different console).

And this is why GDM was freezing the computer as well, where KDM didn't: 
GDM starts X servers in a different order than KDM does.


This GDM config file will boot into a multiseat station:

[servers]
0=Standard0
1=Standard1

[server-Standard0]
name=Standard server 0
command=/usr/bin/Xorg -nolisten tcp -layout seat1 -sharevts -novtswitch -isolateDevice PCI:2:5:0

[server-Standard1]
name=Standard server 1
command=/usr/bin/Xorg -nolisten tcp -layout seat0 -sharevts -novtswitch -isolateDevice PCI:1:00:0


Where this one will hard-freeze the machine (note that the order of X servers is switched):

[servers]
0=Standard0
1=Standard1

[server-Standard0]
name=Standard server 0
command=/usr/bin/Xorg -nolisten tcp -layout seat0 -sharevts -novtswitch -isolateDevice PCI:1:00:0

[server-Standard1]
name=Standard server 1
command=/usr/bin/Xorg -nolisten tcp -layout seat1 -sharevts -novtswitch -isolateDevice PCI:2:5:0



I use xorg 1.4.2 and Linux kernel 2.6.28.
PCI:1:00:0 is AGP RV350 AR [Radeon 9600] card.
PCI:2:5:0 is PCI RV280 [Radeon 9200 PRO] (rev 01) card.

Ideas?


-- 
Tomasz Chmielewski
http://wpkg.org