6.0-BETA1: ATA RAID rebuild not working

Hello,

I am having trouble rebuilding my ATA / SATA RAIDs with 6.0-BETA1.

I have tried it on:
     Intel SCB2 with onboard Promise PDC20267 UDMA100 controller
     Intel 875WP3 with onboard ICH5 SATA150 controller
         (Using PseudoRAID, not Intel MatrixRAID...)

# atacontrol status ar0
ar0: ATA RAID1 subdisks: DOWN ad6 status: DEGRADED

# atacontrol addspare ar0 ad4
ad4: inserted into ar0 disk0 as spare

# atacontrol rebuild ar0

# atacontrol status ar0
ar0: ATA RAID1 subdisks: ad4 ad6 status: REBUILDING 0% completed

And then it just sits at 0% forever. I started a rebuild process on  
the Promise this friday, and it is still at 0%.

During my testing I noticed that when running atacontrol rebuild, a  
dd process shows up. What is it for?

root    546  0.0  0.3  3240  2760  p0- DNL  Fri01PM   0:00.01 /bin/dd  
if=/dev/ar0 of=/dev/null bs=1m

(note, it has run since friday)

Tracing this process show the following:
sched_switch(c3885300,0,1) at sched_switch+0x177
mi_switch(1,0) at mi_switch+0x270
sleepq_switch(d7540f08,ececabc4,c0637469,d7540f08,0) at sleepq_switch 
+0xe0
sleepq_wait(d7540f08,0,0,c085c10e,e52) at sleepq_wait+0x30
bwait(d7540f08,4c,c085429d) at bwait+0x47
physio(c381be00,ececacbc,0,100000,c381be00) at physio+0x1db
devfs_read_f(c3859000,ececacbc,c3ae7780,0,c3885300) at devfs_read_f+0x87
dofileread(c3885300,4,c3859000,ececacbc,ffffffff) at dofileread+0x85
kern_readv(c3885300,4,ececacbc,804f000,100000) at kern_readv+0x36
read(c3885300,ececad04,3,1,246) at read+0x45
syscall(3b,3b,3b,2104,bfbfed40) at syscall+0x22f
Xint0x80_syscall() at Xint0x80_syscall+0x1f
--- syscall (3, FreeBSD ELF32, read), eip = 0x280b9727, esp =  
0xbfbfec8c, ebp = 0xbfbfecd8 ---

db> show locks
exclusive sleep mutex Giant r = 0 (0xc091dba0) locked _at_ /usr/src/sys/ 
kern/kern_intr.c:544


Frode Nordahl
frode_at_nordahl.net