mps driver instability under stable/8

[Dmitry Morozovsky]

Dear Ken,

I have SuperMicro Server with mps driver you managed, with 24 SATA disks under 
SAS x36 expander with large ZFS

Sometimes, under random disk load such as daily find, it lost all its devices:

[-- MARK -- Fri Apr 29 03:00:00 2011]
mps0: IOC Fault 0x40005900, Resetting^M
(pass20:mps0:0:22:0): SCSI command timeout on device handle 0x0020 SMID 442^M
mps0: IOC Fault 0x40001500, Resetting^M
(da19:mps0:0:21:0): SCSI command timeout on device handle 0x001f SMID 172^M
(da19:mps0:0:21:0): SCSI command timeout on device handle 0x001f SMID 511^M
(da20:mps0:0:20:0): SCSI command timeout on device handle 0x001e SMID 240^M

..

(da4:mps0:0:0:0): SCSI command timeout on device handle 0x000a SMID 844^M
(da22:mps0:0:23:0): SCSI command timeout on device handle 0x0021 SMID 713^M
(da18:mps0:0:22:0): SCSI command timeout on device handle 0x0020 SMID 603^M

and hangs there forever (in zio state).

I've prepared debugging kernel with DDB and would be glad to help catch the 
situation.

Thanks!

-- 
Sincerely,
D.Marck                                     [DM5020, MCK-RIPE, DM3-RIPN]
[ FreeBSD committer:                                 marck at FreeBSD.org ]
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*** Dmitry Morozovsky --- D.Marck --- Wild Woozle --- marck at rinet.ru ***
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