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Date: Tue, 17 May 2011 15:38:33 +0300
From: Andriy Gapon <avg@FreeBSD.org>
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To: Jeremy Chadwick <freebsd@jdc.parodius.com>
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Cc: Charles Sprickman <spork@bway.net>, stable@FreeBSD.org
Subject: Re: 8.1R possible zfs snapshot livelock?
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on 17/05/2011 15:23 Jeremy Chadwick said the following:
> So for Charles' situation, the next time it happens what would be useful
> for him to provide?  The best I could come up with was to induce doadump
> then reboot to get the system up/working again, and then use kgdb
> after-the-fact.

This is one of the best things to do, if possible.
In this case all the potentially useful info would be preserved.

Less drastic approach to hanged I/O debugging is to find out where
processes/threads are actually stuck.  E.g. using procstat -kk.

-- 
Andriy Gapon