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To: David Malone <dwmalone@maths.tcd.ie>
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
In-Reply-To: Your message of "Sun, 17 Aug 2003 10:56:07 BST."
             <20030817095607.GA83750@walton.maths.tcd.ie> 
Date: Sun, 17 Aug 2003 13:12:02 +0200
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cc: Robert Watson <rwatson@freebsd.org>
cc: current@freebsd.org
cc: Kris Kennaway <kris@obsecurity.org>
Subject: Re: LOR with filedesc structure and Giant 
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In message <20030817095607.GA83750@walton.maths.tcd.ie>, David Malone writes:
>On Sat, Aug 16, 2003 at 10:18:43PM +0200, Poul-Henning Kamp wrote:
>> At one point we have to say "Well, the locks we have above are solid,
>> but we need to drop Giant below here" but if Witness sees a
>> PICKUP_GIANT() as an acquisition of Giant, rather than as a
>> resumption of Giant, this clearly does not work.
>
>Wouldn't the risk of deadlock be real, even if it is only a resumption
>of Giant? I guess another option is to drop all the locks that are
>held and reqcquire all of them in the right order...

There is no risk at the point where I drop Giant (as far as I have been
able to work out).  Dropping all the locks would not work, because it
is the "other" locks held which make dropping Giant safe.

-- 
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.