Bug 20351

Created attachment 23366 [details]
xorg.conf

Steps to reproduce:

1. use EXA with EXAVSync option enabled
2. launch 1-2 instances of konsole or konqueror (3.5.10)

This results in an immediate lockup. Two cases:
a. If the kernel drm and radeon modules are loaded and DRI works, this means that the mouse can still move sluggishly across the screen, sysrq commands work, and commands will still work from an existing ssh session. It is not possible to switch to VT or launch a new and working X instance.

b. Without the kernel modules, the lockup is complete. No sysrq commands work, mouse doesn't move, ssh session is lost.

System:
OS: Gentoo
kernel: 2.6.28-gentoo-r2 (uvesafb is used with v86d-0.1.9)
xorg-server: 1.5.3-r2 (also tested with 1.6.0)
mesa: 7.3
libdrm: 2.4.5

Using git-bisect on xf86-video-ati, it seems that the guilty commit is http://cgit.freedesktop.org/xorg/driver/xf86-video-ati/commit/?id=4d98acbca2e630056bf56cdcd0e23007fded2ced (between versions 6.9.0 and 6.10.0).

Bugs #13998 and #18664 might be related to this one.

Nothing shows up about the lockup in Xorg.0.log, dmesg or messages.

Removing EXAVSync from the device options means that no immediate lockup occurs on launching qt3 using applications, but that might only postpone it.