Every so often, I'll be using my CDROM and some process
(usually cp) will go into disk lock state and just sit there
for evermore.  I've only noticed this with recent -current.
Subsequently, ps axcu says:

mark     27277  0.0  0.0   172     4 p4- DW         -  0:00.00 cp

obviously I can't kill the resulting undead process, nor can
I umount the cdrom.  Any thoughts?

The CDROM is a middle-aged samsung 40x ATAPI, running on a
relatively new -current.  Like many CDROMS it apparently
reports DMA capability incorrectly, so I've added an
appropriate option to the kernel config to put it in PIO
mode.

NetBSD 1.5S (LORIEN) #5: Fri Mar  9 10:44:46 GMT 2001
    mark@lorien:/m/1f/current/src/sys/arch/i386/compile/LORIEN
cpu0: AMD K6-2 (586-class), 551.28 MHz
[...]
cd0 at atapibus1 drive 1: <SAMSUNG SC-140B, , BS12> type 5 cdrom removable
cd0: 32-bit data port
cd0: drive supports PIO mode 4, DMA mode 2
cd0(pciide0:1:1): using PIO mode 4

Mark <><