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Date: Fri, 4 Sep 2015 22:32:07 +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 Fri, Sep 04, 2015 at 11:42:38AM -0700, John Baldwin wrote:
> Hmm, looking at /dev/ptmx, it handles this by not doing a clone on open,
> but instead using a d_fdopen routine and explicitly setting up the new
> file descriptor as if it had opened the equivalent named device.  Perhaps
> that is what I should do instead in my tap change.  If I go that route,
> then I think that fdevname/devname would already DTRT without needing a
> new cdevsw method.

There is probably some fine difference between pts, which are typically
fully managed and configured by master using the file descriptor, and
cloned network interfaces, where you usually allow external processes to
do the work.  But if it works for tap, great.

Also, you should have noted D3557 (csw d_devname), just in case ?