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Date:      Sat, 8 Dec 2001 20:40:15 -0500 (EST)
From:      Robert Watson <rwatson@FreeBSD.ORG>
To:        Poul-Henning Kamp <phk@critter.freebsd.dk>
Cc:        Terry Lambert <tlambert2@mindspring.com>, Dave Rufino <dr263@hermes.cam.ac.uk>, Alfred Perlstein <bright@mu.org>, freebsd-hackers@FreeBSD.ORG
Subject:   Re: statefulness in character device drivers 
Message-ID:  <Pine.NEB.3.96L.1011208203911.57264T-100000@fledge.watson.org>
In-Reply-To: <47779.1007808692@critter.freebsd.dk>

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On Sat, 8 Dec 2001, Poul-Henning Kamp wrote:

> >> The issue is non-trivial to fix because we currently don't pass
> >> dup(2) events through the vnode layer.
> >
> >Are you sure this is even necessary?
> >
> >They are talking about "per-open", not "per-fd-instance" data,
> >which could easily exclude dup, dup2, and fcntl(f_DUPFD).
> 
> If you don't include dup/dup2/fnctl in your accounting, you can only
> reliably tell "first open", "another open", "some close"  and "final
> close".  You an modulate this with the pid, but you still have no idea
> what is going on in any amount of detail. 

Generally speaking, the information of interest to me would be "first
open" for a particular struct file, and "last close".  Other migration of
the reference to struct file around the system would not be so useful: if
a process wants new references to be visible at the device layer, they can
always open more references using new struct files.

Robert N M Watson             FreeBSD Core Team, TrustedBSD Project
robert@fledge.watson.org      NAI Labs, Safeport Network Services




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