While looking at a bug report [1] I found that the immediate cause of the crash
was in that specific case the reference cp->cmd for a printk:
/*
* The device didn't switch to MSG IN phase after
* having reselected the initiator.
*/
case SIR_RESEL_NO_MSG_IN:
scmd_printk(KERN_WARNING, cp->cmd,
"No MSG IN phase after reselection\n");
goto out_stuck;
Unfortunately cp (that is returned by sym_ccb_from_dsa()) is NULL. This probably
is as old as 2.6.24 when this patch added the scmd_printk:
commit 3fb364e089e05c35ead55a08d56d3004193681f6
Author: Matthew Wilcox <matthew@xxxxxx>
Date: Fri Oct 5 15:55:10 2007 -0400
[SCSI] sym53c8xx: Use scmd_printk where appropriate
A quick research looks like it might be other cases where this happened[2].
Maybe more often (or solely?) when running in a VM (KVM). I even found some post
that looks like it tries to fix just this problem[3].
However without more knowledge about that driver it could also be a problem in
the hardware emulation so that normally cp == NULL should never happen. Or it
might be that the emulation is just running sufficiently "different" to cause
races to happen which never would be observed on real hardware.
Would [3] still make sense?
Thanks,
Stefan
[1] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/992328
[2] http://www.mail-archive.com/kvm@xxxxxxxxxxxxxxx/msg08927.html
[3] https://lkml.org/lkml/2010/11/18/495
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