James Bottomley [off-list ref] wrote:

On Thu, 2005-09-15 at 15:57 -0400, James Bottomley wrote:

quoted

I haven't had time to review the eh changes, but I was going to reply to
the other one (basically there's a better way to try to close the device
add/host remove race using the host state model).

Let me complete the SCSI process and I'll take them through the scsi-rc-
fixes tree.

Well, I think the symptoms are racing scsi_remove_host() calls and the
solution is to enforce the state model on removal (as in if the host is
already in the remove state, don't try to remove it again).

Could you try the patch here:

http://marc.theaimsgroup.com/?l=linux-scsi&m=112613077011571

And see if it will fix the problem?

A side effect of not applying Alan's previous patch that added
SHOST_RECOVERY to the SHOST_CANCEL: state is that we will not move to the
SHOST_CANCEL and subsequently not to SHOST_DEL state if the eh is active
during the start of scsi_remove_host. I sent mail on the 7th indicating to
include that state change hunk of the diff, but I guess that overlapped
with your newer state changes.
http://marc.theaimsgroup.com/?l=linux-scsi&m=112238726326927&w=2

In looking at the state model introduced by your patch I believe there may
still be a state model race issue if the recovery completes just after
the "if (!scsi_host_set_state(shost, SHOST_CANCEL))" call in
scsi_remove_host (maybe I am just looking to quickly at the state
updates).

I still do not understand as I asked in a previous comment why we are not
shutting down the eh_thread in scsi_remove_host and also why simpler state
model updates could not solve the problem.

I believe I also indicated that we could enhance scsi_error to shutdown
faster during this state which should only be a performance improvement.

-andmike
--
Michael Anderson
andmike@us.ibm.com


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