[linux-lvm] more info on the hang with 2.6.15-rc5

[Sebastian Kuzminsky <seb@highlab.com>]

Now it works, but I dont trust it one bit.

I had been seeing almost immediate, perfectly repeatable hard lockups
in 2.6.15-rc5 and 2.6.15-rc5-mm3, when using sata_mv, RAID, and LVM
together.  Nothing in the syslog or on the console, and the system is
totally unresponsive to the keyboard & network.

My hardware setup is: four Seagate Barracuda 500 GB disks, on a Marvell
MV88SX6081 8-port SATA-II PCI-X controller, on a PCI-X bus (64/66).

The disks work great when accessed directly.  They work great when used
as four PVs for LVM, and when assembled into a 4-disk RAID-6.

But when I make a RAID-6 array out of them, and use the array as a PV,
the system would hang completely, within seconds.  (This is with LVM
2.02.01, libdevicemapper 1.02.02, and dm-driver 4.5.0.)

I turned on all the debugging options in the kernel config hoping to get
some insight, but this "debug" kernel doesnt crash.  It's running fine,
and I'm pounding on it.  A timing problem in the interaction between
LVM and RAID?  Some kind of wierd heisenbug....


I'd be happy to do any debugging tests people suggest.


-- 
Sebastian Kuzminsky