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Date: Tue, 29 May 2012 09:54:28 -0600 (MDT)
From: Warren Block <wblock@wonkity.com>
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	(wonkity.com [127.0.0.1]); Tue, 29 May 2012 09:54:28 -0600 (MDT)
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Subject: Swap files and panics
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Recently I rearranged partitions on an SSD.  The swap partition was 
eliminated in favor of a swap file on /usr.  This works, allows TRIM 
support on the swap space, and is easier to resize than a partition.

However, sometimes the system panics on shutdown.  It happens after 
"syncing disks", so the filesystems are fine, but it's disconcerting.

I suspect but haven't yet managed to prove that it's only when swap is 
not empty.  A race condition involving when the filesystems are 
unmounted?  Or should there be some code in /etc/rc.d/addswap to run 
swapoff before shutdown?

This is on a very recent 9-STABLE amd64, i5 2500K.

rc.conf:
swapfile="/usr/swap/swap"