lpfc: system freezing if FC connection is broken under load

[Bodo Stroesser <bstroesser@fujitsu-siemens.com>]

Hi,

my dual Xeon machine freezes, if connection between
FC switch and tape drives is broken while writing to tapes.

There is one SCSI target with 16 tape LUNs connected to my
FC controller via FC switch. I can reproduce the problem by
starting "dd if=/dev/zero of=/dev/st[0-7] bs=256K" on the
first 8 LUNs. Then I unplug the connection between switch and
tapes.

It doesn't matter if using LP9802 or one channel of LP9402DC.
The problem happens immediately after cfg_nodev_tmo has
run out. If nodev_tmo is changed, time from breaking connection
to machine freezing changes accordingly.

After the problem happened, even NMIs no longer are handled.
I added nmi_watchdog=1 to cmdline and added some simple code
to nmi handler, that writes the nmi counter directly to video ram.
In case of error, nmi no longer counts (but I have no idea, how
this can happen, maybe there is some HW bug).

What could I do to analyze the problem?

Please CC me, I'm not on the list.

Regards
	Bodo