+++ This bug was initially created as a clone of Bug #473555 +++

I am having the same problem with Fedora 9 + latest updates, no Fedora 10 involved.  In addition to the problems described above, I get stray lines all over the screen.

--- Additional comment from angavrilov on 2008-11-29 06:19:13 EDT ---

Created an attachment (id=325079)
ioctl backtrace log.bz2

A log of ioctl backtraces from the debugger.
Points of freeze are marked by "----------".

--- Additional comment from angavrilov on 2008-11-29 06:15:23 EDT ---

Created an attachment (id=325078)
Xorg.0.log

--- Additional comment from angavrilov on 2008-11-29 06:14:23 EDT ---

Created an attachment (id=325077)
xorg.conf

Description of problem:

After using KDE4 with XRender desktop effects for several hours,
X rendering operations suddenly start slowing down, which quickly
proceeds to a complete X freeze. The rest of the system remains
operative, so it is possible to reboot it either remotely, or
through the ATX power button.

Version-Release number of selected component (if applicable):

Fedora 9 upgraded to Fedora 10 + latest updates.

Updating to kernel-2.6.27.5-123.fc10.i686
and xorg-x11-drv-ati-6.9.0-58.fc10.i386 did not have any effect.

How reproducible:

Once or twice a day.

Additional info:

Attaching a debugger shows that X actually continues working,
but some ioctls hang in drm_fence_object_wait for minutes.

I'll try running with nomodeset, and without xorg.conf next.