Linux 4.1 BT Crash

My Macbook Air 4,2 with Ubuntu 15.10 would start to a black screen. The boot process went so far that you could hear the ubuntu drums in the background, but other than that nothing was responding.

There is a kernel bug regarding this at ​https://bugzilla.kernel.org/show_bug.cgi?id=100651

I’m running refind, and tried to find ways of booting to console. What worked was pressing F2 twice for boot options, and add systemd.unit=emergency.target to the boot params. “text” boot param did not work, and I couldn’t find it documented anywhere.

Once booted, dmesg ended with
[ 774.467449] Bluetooth: hci0: BCM: Read verbose config info failed (-16) + a couple of more rows regarding wifi scanning. So Bluetooth was my primary suspect. I remounted the root FS with mount -o remount,rw /dev/sdaX / and edited /etc/modprobe.d/blacklist.conf to include a line blacklist btbcm.

Now the compy boots. The btbcm kernel module is still loaded later in the boot sequence (probably autoloading as suggested by ​https://wiki.debian.org/KernelModuleBlacklisting), but no hang! Yay.