zio->io_cv deadlock

[Kevin Day]

I'm playing with a -CURRENT install from a couple of weeks ago.  
Everything seems okay for a few days, then eventually every process  
ends up stuck in zio->io_cv. If I go to the console, it's responsive  
until I try logging in, then login is stuck in zio->io_cv as well.  
Ctrl-Alt-Esc drops me into ddb, but then ddb hangs instantly.

Nothing on the console or syslog before it hangs.

Anyone seen anything similar?

-- Kevin


Possibly relevant info:

8 core Opteron
64GB RAM

da1 at twa0 bus 0 target 0 lun 1
da1: <AMCC 9650SE-12M DISK 3.08> Fixed Direct Access SCSI-5 device
da1: 100.000MB/s transfers
da1: 4678158MB (9580867585 512 byte sectors: 255H 63S/T 596381C)

server5# zpool list
NAME   SIZE   USED  AVAIL    CAP  HEALTH  ALTROOT
z     4.44T  1.19T  3.25T    26%  ONLINE  -

server5# zpool status -v
   pool: z
  state: ONLINE
  scrub: none requested
config:

	NAME        STATE     READ WRITE CKSUM
	z           ONLINE       0     0     0
	  da1       ONLINE       0     0     0

errors: No known data errors

server5# cat /boot/loader.conf
vm.kmem_size_max="2048M"
vm.kmem_size="2048M"
vfs.zfs.arc_max="100M"
zfs_load="YES"
vfs.root.mountfrom="zfs:z"


(tried lowering arc_max, didn't seem to help)