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Date: Thu, 29 Oct 2009 22:49:33 -0500
From: "James R. Van Artsdalen" <james-freebsd-current@jrv.org>
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Cc: Alexander Motin <mav@freebsd.org>
Subject: CAM/SIIS CAM_CMD_TIMEOUT hangs
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I have problems with I/O hanging due to CAM/SIIS not handling the
CAM_CMD_TIMEOUT error.
Hangs happen every few hundred GB to every few TB.
The disks are behind SATA port multipliers.

This command un-hangs the drive and lets things run again:

# camcontrol reset all

I assume this is sending a soft reset to the disk drive but haven't
checked yet.

Is there a way xpt_done() or such might notice a CAM_CMD_TIMEOUT and
inject a "soft reset" request at the head of the I/O queue (to run
before the timed-out command retries)?