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To: freebsd-current <freebsd-current@freebsd.org>
From: Julian Elischer <julian@freebsd.org>
Subject: crash on process exit.. current at about r332467
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Date: Mon, 23 Apr 2018 22:50:43 +0800
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back trace at:  http://www.freebsd.org/~julian/bob-crash.png

If anyone wants to take a look..

In the exit syscall, while deallocating a vm object.

I haven't see references to a similar crash in the last 10 days or 
so.. But if it rings any bells...