[ltp] x hang switching screens using xrandr

[Phil Shotton]

Replying to my own post...

Phil Shotton wrote:
>
> I regularly switch my laptop between twin external monitors (work) and 
> single external with laptop LCD (home), and wrote two scripts to 
> switch between the two using xrandr (having suspended/resumed):
>
> home.sh
> xrandr --output VGA-0 --auto
> xrandr --output DVI-0 --off
> xrandr --output LVDS --auto
> xrandr --output VGA-0 --auto --right-of LVDS
>
> work.sh
> xrandr --output DVI-0 --auto
> xrandr --output VGA-0 --auto
> xrandr --output LVDS --off
> xrandr --output DVI-0 --auto
> xrandr --output VGA-0 --auto --left-of DVI-0
It's this line that causes the problem. Even if run on its own without 
any of the intervening lines. x-session-manager is then stuck with 
exactly the same trace as below. An interrupted system call failing to 
restart or deadlock in the bowels of X??

This problem is happening regularly and is very annoying. It means 
closing all apps before screen switch just in case I have to restart X. 
Any ideas?
>
> These used to work fine with Ubuntu Hardy, with the latest radeon 
> drivers from git. Now I'm running Ubuntu 8.10 with the standard distro 
> x support which works really nicely, except about 30% of the time when 
> switching from home to work the screen hangs. Today I managed a bit 
> more investigation.
>
> When running work.sh, the second xrandr call reports:
>    X Error pof failed request: BadMatch (invalid parameter attributes)
>       Major opcode of failed request: 153 (RANDR)
>       Minor opcode of failed request: 21 ()
>       Serial number of failed request: 18
>       Current serial number in output stream: 18
>
> The rest of the xrandr calls in the script execute, but the last one 
> appears to hang. At that stage both external monitors are displaying 
> but in clone mode, the laptop screen is disabled, the mouse moves and 
> keyboard is scanned, but I'm unable to do anything. I can't select a 
> different window, non of the panel icons responds, the cpu monitor is 
> frozen.
>
> I can switch to a virtual terminal and back to X. I tried running 
> strace on various bits of the X system from the vt. The X server 
> appeared to be behaving normally, but when I ran strace on the 
> x-session-manager it appeared to be hung. Output was something like:
>    thread 17095 restart_syscall(... unfinished)
>    thread 17241 read(19,
>
> (the last line really was truncated as shown).
> Trying to exit using control-c, strace reported detach from 17095 but 
> failed to detach from 17241.
> Back to X, I killed the X-server with ctrl-alt-backspace. Screens 
> blanked, but x did not restart. Back to the vt, found the 
> x-session-manager was still running. kill did not kill it, but kill -9 
> did, and gdm then kicked in and restarted the x server.
>
> So it looks like sometimes xrandr does somethink that hangs up 
> x-session-manager. Any ideas?
>
> Machine is T60p, running stock kernel 2.6.27-9-generic, using radeon 
> v6.9.0 with X server 1.5.2 (all stock from Ubuntu distro).
> Video is ATI Technologies Inc M56GL [Mobility FireGL V5250]
>
> Thanks
> Phil