Description of problem:
I  have two computers using IMSM RAID with F17.  Neither has been able to shut down for a while.

Version-Release number of selected component (if applicable):
mdadm-3.2.5-4.fc17.x86_64
kernel 3.5.2-3.fc17.x86_64

How reproducible:
Happens every time

Steps to Reproduce:
1. Shutdown or Reboot

  
Actual results:
Computer freezes

Expected results:
Computer should successfully poweroff or reboot


Additional info:

The two computers are a Dell Optiplex 755 and a Dell Optiplex 960.

When I use the Alt-SysRq-O combination on the Optiplex 755, I see the following messages.  After these messages are printed out, the Alt-SysRq key combinations don't work anymore.

sd 8:0:0:0: [sdg] Synchronizing SCSI Cache
sd 8:0:0:0: [sdg] Stopping disk
sd 1:0:0:0: [sdb] Synchronizing SCSI Cache
sd 1:0:0:0: [sdb] Stopping disk
sd 0:0:0:0: [sda] Synchronizing SCSI Cache
sd 0:0:0:0: [sda] Stopping disk
pci 0000:00:1e.0: wake-up capability enabled by ACPI
 pci0000:00:wake-up capability enabled by ACPI
usb 2-2: USB disconnect, device number 2
sd 6:0:0:0: Device offlined - not ready after error recovery 
ata4.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen
sr 2:0:0:0: CDB
Get event status notification 4a 01 00 00 10 00 00 00 08 00
ata4.00: cmd a0/00:00:00:08:00/00:00:00:00:00/a0 tag 0 pio 16392 in
         res 40/00:03:00:00:00/00:00:00:00:00/a0 Emask 0x4 (timeout)
ata4.00: status { DRDY }
ata4: hard resetting link
ata3.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen
sr 3:0:0:0: CDB:
Get event status notification: 4a 01 00 00 10 00 00 00 08 00
ata3.00: cmd a0/00:00:00:80:00/00:00:00:00:00/a0 tag 0 pio 16392 in
         res 40/00:03:00:00:00/00:00:00:00:00/a0 Emask 0x4 (timeout)
ata3.00: status: { DRDY }
ata3: hard resetting link
ata4: failed to reset engine (errno=-5)
ata3: railed to reset engine (errno=-5)
ata4: softreset failed (1st FIS failed)
ata4: hard resetting link
ata3: softreset failed (1st FIS failed)
ata3: hard resetting link
ata4: failed to reset engine (errno=-5)
ata3: failed to reset engine (errno=-5)
ata4: softreset failed (1st FIS failed)
ata4: hard resetting link
ata3: softreset failed (1st FIS failed)
ata3: hard resetting link
ata4: failed re reset engine (errno=-5)
ata3: failed to reset engine (errno=-5)
ata4: softreset failed (1st FIS failed)
ata4: limiting SATA link speed to 1.5 Gbps
ata4: hard resetting link
ata3: softreset failed (1st FIS failed)
ata3: limiting SATA link speed to 1.5 Gbps
ata3: hard resetting link
ata4: failed to reset engine (errno=-5)
ata3: failed to reset engine (errno=-5)
ata4: softreset failed (device not ready)
ata4: reset failed, giving up
ata4.00: disabled
ata4: EH complete
ata3: softreset failed (device not ready)
ata3: reset failed, giving up
ata3.00: disabled
ata3: EH complete