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Date: Wed, 27 Apr 2011 02:17:09 +0200
From: Bartosz Fabianowski <freebsd@chillt.de>
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To: Kostik Belousov <kostikbel@gmail.com>
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Cc: freebsd-hackers@freebsd.org, Hans Petter Selasky <hselasky@c2i.net>
Subject: Re: Is there some implicit locking of device methods?
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> If you needs per-file private data for cdev, you would be better served
> by cdevpriv(9) KPI. Cloning is too hard to use correctly for such task.

Thanks, I just got that working. To help those going down a similar path 
in the future, I would like to note quickly that the following must be 
added to the cdevsw structure to ensure proper clean-up:

.d_flags = D_TRACKCLOSE

I just spent hours debugging panics until I realized only the last 
close() was triggering a call to my .d_close method.

- Bartosz