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To: Robert Watson <rwatson@FreeBSD.org>
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
In-Reply-To: Your message of "Mon, 07 Jul 2008 16:30:06 +0100."
	<20080707162733.V63144@fledge.watson.org> 
Date: Mon, 07 Jul 2008 16:05:54 +0000
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Sender: phk@critter.freebsd.dk
Cc: arch@FreeBSD.org, Sergey Babkin <babkin@verizon.net>
Subject: Re: Proposal: a revoke() system call 
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In message <20080707162733.V63144@fledge.watson.org>, Robert Watson writes:

>>> achieve something of the same end by opening /dev/null and then dup2()'ing 
>>> to the file descriptor you want to revoke, perhaps?  Right now there's a 
>>> known
>>
>> That's a great idea. I haven't thought about it. It should do everything.
>
>Right, and possibly this means that no additional kernel support is required 
>-- we just make it a libc or libutil interface.

I can't see how that could possibly work...

If you do a dup2(), the original fd is closed, and that still does not
release all threads that may be sleeing on it in device drivers.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.