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Date: Thu, 3 Sep 2015 12:47:27 +0300
From: Konstantin Belousov <kostikbel@gmail.com>
To: John Baldwin <jhb@freebsd.org>
Cc: freebsd-drivers@freebsd.org, Leonardo Fogel <leonardofogel@yahoo.com.br>
Subject: Re: Race conditions
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On Wed, Sep 02, 2015 at 10:59:12AM -0700, John Baldwin wrote:
> If we allow a cdevsw to override how devname works, then that would probably
> be sufficient on its own.  I don't think you would need to change the
> /dev/tapX devices at all.  The cdevpriv for /dev/tap desciptors would have a
> reference to the /dev/tapX device it is using and return that device's name
> in the devname override.
You mean, the consumers of tap use fdevname(3), not devname(3) ?  Since
for devname(), there is no access to cdevpriv.

> 
> Another option that I had started to play with previously is to let devices
> auto-created by /dev/tap set an internal 'destroy-on-close' flag.  That
> seems a bit more heavyweight, but it might also be simpler to implement?

Could you, please, clarify, how this would help to handle the race at
open ?