ahci(4) hang reproduced, this time it was cdrdao scanbus

[Juergen Lock]

Hi!

 I wanted to burn an audio cd today and ran `cdrdao scanbus' to find out
cdrdao's --device arg for the optical drive (turns out its the same
numbering as camcontrol devlist reports i.e.
	<PIONEER DVD-RW  DVR-216D 1.09>    at scbus3 target 0 lun 0 (cd1,pass3)
becomes --device 3,0,0) - after which ahci(4) hung again with the board's
disk access led on solid.  This time tho I took a photo:
	http://people.freebsd.org/~nox/ahcihang1.jpg
Taking a dump failed again too:
	http://people.freebsd.org/~nox/ahcihang2.jpg

 cdrdao is in ports as sysutils/cdrdao and is mostly used for writing
or cloning audio cds or vcds.  (I haven't tried cdrecord's -scanbus
command tho I wouldn't be surprised if it behaves the same...  cdrecord
is in ports as sysutils/cdrtools and sysutils/cdrtools-devel; you usually
want cdrtools-devel.)

 Oh and btw, the actual burning (after reboot + fsck) then went just
fine, its just the scanbus command that ahci(4) apparently doesn't like...

 Thanx,
	Juergen