Multi-Monitor + DDD + Radeon = Xorg crash

[sandain]

So this is a bit odd..

I just installed DDD via Synaptic on my laptop for a little debugging that I need to do. Each time that I have tried running DDD, X has crashed shortly after the DDD logo was displayed. After some trial and error, I discovered that this only happens when I have a second monitor plugged into the HDMI port on my laptop, it functions as expected with only one monitor (LVDS). I'll test for this same crash when a VGA monitor is plugged in as soon as find a spare cable..

This may be a bug in DDD, but I suspect it is in the graphics driver stack instead. Does anyone here have any ideas?

Chipset: M76 (HD2600)
Distro: Ubuntu 11.04
Kernel: Stock - 2.6.38-10-generic x86_64
libdrm: Xorg edgers - 2.4.26+git20110604.6dd804c5-0ubuntu0sarvatt~natty
xserver: Xorg edgers - 1.10.1+git20110526.a8721393-0ubuntu0sarvatt~natty
ddx: Xorg edgers - 6.14.99+git20110613.41eb1fbb-0ubuntu0sarvatt~natty
mesa: Xorg edgers - 7.11.0+git20110614.7d488ade-0ubuntu0sarvatt~natty

The Xorg log file only mentions 'ddxSigGiveUp: Closing log' with no other apparent errors.

[sandain]

I spent some more time playing around with this issue, and have a few new items to report:

X does not crash when a VGA cable replaces the HDMI cable to the same monitor.

Upgrading to a 2.6.39 kernel does not fix the crash.

Purging the Xorg-edgers PPA does fix the crash. By cherry picking packages from the PPA, I was able to narrow the regression down to the DDX. Version 6.14.0 of xserver-xorg-video-radeon that comes stock with Ubuntu 11.04 works as expected. Version 6.14.99 as provided by Xorg-edgers crashes as described before.

When I find some more time, I'll take a look at compiling the latest DDX from git and start playing around with finding the offending commit.