Help: problem with X11 / XFree86-DRI ; who to blame?

[Gian Paolo Mureddu]

Rob escribió:
>
> Hi,
>
> My OS is an up-to-date version of Fedora 7 on a Intel based PC.
>
> I use a particular academic/scientific video rendering software VMD
> ( http://www.ks.uiuc.edu/Research/vmd/ ).
> This software uses GLX/Mesa heavily.
>
> My day-to-day window manager is XFCE. When I use VMD, it immediately
> freezes keyboard/mouse on my console as soon as any video rendering
> activity occurs. The typical error message in /var/log/messages is:
>
>     kernel: [drm:i915_wait_irq] *ERROR* i915_wait_irq: EBUSY --
>                rec: 147447 emitted: 147473
>
> However, when I switch to KDE window manager, all this does not occur.
>
> Obviously I first blamed XFCE, but the developers there are convinced
> that the Xorg and/or related X11-video drivers are to be blamed.
>
> Eventually I solved the problem: I disabled XFree86-DRI in the file
> /etc/X11/xorg.conf.
>
> Is there anybody who knows about this matter and can help me
> understand what's going on?
> I'd like to report this problem somewhere, but who is to be blamed?
>   XFCE ? (they deny)
>   Xorg ?
>   Fedora ?
>   XFree86-DRI ?
>
> Thanks,
> Rob.
The kernel error message printed to /var/log/messages and the fact that 
it does show on XFCE only (and not KDE or presumably other window 
manager), indeed suggests that the driver is to blame. It's been a while 
since Xorg substituted XFree86 in Linux distributions, however the DRI 
method for rendering 3D graphics was kept from it. At any rate, the 
breakdown of the problem seems to be that XFWM4 the actual "window 
manager" in XFCE, does include a compositor engine. Do you have it 
enabled? Do you have the Composite extension enabled in 
/etc/X11/xorg.conf? Do you have AIGLX enabled in xorg.conf? Do you run 
another compositing manager in XFCE (say, Compiz or Beryl)? I'd be 
inclined to think that it is indeed the driver which is at fault, this 
hints it out:

kernel: [drm:i915_wait_irq] *ERROR* i915_wait_irq: EBUSY --
               rec: 147447 emitted: 147473

DRM is kernel-side component for DRI to work. DRI stands for Direct 
Rendering Infrastructure, and DRM (unlike Digital Restrictions 
Management) stands for Direct Rendering Manager. Are you running 32 or 
64-bits? I know it is a shot in the dark, but maybe there is a problem 
with the IRQ table, maybe adding 'noapic' as a kernel command line 
argument at boot might solve this? Or maybe checking the IRQ table in 
the BIOS might also help? Is this a dual core/HT CPU? Are you running 
the IRQ balance system service? (check with system-config-services)

Sorry to have many more questions than answers for you, but the 
information you provide is scarce... Bottom line, I'd be inclined to 
think about an IRQ table/balance problem or a driver problem, rather 
than anything else.