disabling cape in device tree locks up kernel

The very helpful write-up on how to use the cape manager (http://elinux.org/BeagleBone_and_the_3.8_Kernel#Cape_Manager_and_Device_Tree_Overlays) suggests that one can disable a cape by echoing the cape number to the cape mgr like so:

cat /sys/devices/bone_capemgr.9/slots

0: 54:PF—
1: 55:PF—
2: 56:PF—
3: 57:PF—
4: ff:P-O-L Bone-LT-eMMC-2G,00A0,Texas Instrument,BB-BONE-EMMC-2G
5: ff:P-O-L Bone-Black-HDMI,00A0,Texas Instrument,BB-BONELT-HDMI

echo -5 >/sys/devices/bone_capemgr.9/slots

I did this after a “sudo -s” and oddly found myself back in my user shell instead of the root shell. I then wanted to check the situation and tried:

cat /sys/devices/bone_capemgr.9/slots

but that locks up and is unkillable (the process is stuck in a device driver, i.e. “D” state in ps). The only remedy I’ve found is a hard reset (/sbin/reboot doesn’t work). Is this a known issue?

I’ve had the same thing happen to me. i.e. cat slots hanging.

From http://learn.adafruit.com/introduction-to-the-beaglebone-black-device-tree/exporting-and-unexporting-an-overlay

“One thing to note. As of the 6-20-2013 release of Angstrom, unloading various overlays can cause a kernel panic, and cause you to lose your ssh session, along with making the capemgr unpredictable. It’s recommended to just restart your system to unload overlays until that issue is resolved.”

As of right now I do not know if anyone has come up with a fix for this issue.