DTrace of radeonkms on 9.1

[J.R. Oldroyd]

Is there any known magic involved in getting DTrace to do its thing on
9.1-release?

I am trying to use it to debug a memory leak problem with the radeonkms
driver under 9.x.

Firstly, the following sequence works normally:

	boot system
	kldload drm2
	kldload radeonkms
	start xorg
	stop xorg
	kldunload radeonkms
	kldunload drm2

The problem is that, when using xterm, there is a memory leak which
shows as the Free mem counter in "top" reducing rapidly.

The usual printf debugging isn't helping because we are in a heavily
multi-threaded part of the driver and the printfs are being
interleaved in the kernel buffer.  DTrace's function boundary probes
would be a big help if I could only get them to work.

I've built a dtrace kernel per the instructions in the handbook and
on the DTrace wiki page.  I would now like to do this:

	boot system
	kldload dtraceall
	kldload drm2
	dtrace -o dtrace.log -s script.d
		(the script will use fbt probes on various
		functions currently in the drm2 module)
	kldload radeonkms
	start xorg and do various things that provoke the leak
	stop xorg
	kldunload radeonkms
	kill the dtrace script
	kldunload drm2
	kldunload dtraceall

then go look at the log results.

But, the system is stopping dead shortly after the radeonkms load.
It also stops dead if I load radeonkms without starting the dtrace
script.  The presence of the dtraceall module appears to be causing
the radeonkms module load to fail.

Now the radeonkms module does initialize and switch the console to
the graphics mode before the system stops.  There is about 5-10 sec
of what looks like the normal driver init sequence before the system
stops.  When the system stops there is no panic.  It just stops dead.
No keyboard/mouse, no netowrk/ssh - dead.  A hard power-off and reboot
is needed afterwards.

It's perhaps worth mentioning that the leak I am trying to trace is
probably not a simple malloc/free leak.  There are no leak messages
in the log after the normal module load/unload sequence.  This driver
also does VM allocs and manages its own pages and the problem could
be there.

Any suggestions on how to persuade DTrace to work would be great.
Thanks,
	-jr