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Date:      Fri, 7 Feb 2003 13:56:21 -0500 (EST)
From:      Robert Watson <rwatson@FreeBSD.ORG>
To:        Hiten Pandya <hiten@unixdaemons.com>
Cc:        Julian Elischer <julian@elischer.org>, John Baldwin <jhb@FreeBSD.ORG>, FreeBSD current users <current@FreeBSD.ORG>
Subject:   Re: vnode locking question.
Message-ID:  <Pine.NEB.3.96L.1030207135422.82448A-100000@fledge.watson.org>
In-Reply-To: <20030207172327.GA23165@unixdaemons.com>

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On Fri, 7 Feb 2003, Hiten Pandya wrote:

> On Thu, Feb 06, 2003 at 10:53:08AM -0800, Julian Elischer wrote the words in effect of:
> > 
> > On Thu, 6 Feb 2003, John Baldwin wrote:
> > 
> > > On 05-Feb-2003 Julian Elischer wrote:
> > > > 
> > > > Is there ever a case when a vnode is locked for longer than the duration
> > > > of the syscall that locked it?
> > > 
> > > Shouldn't be.  That would be a bug I believe.  Userland threads should
> > > never hold any kernel locks.
> > 
> > That's what I think too but I just thought I'd ask..
> > (NFS worries me a bit)
> 
> If It did, wouldn't that give a panic() with something like: 
> 	"panic: mutex held on exit to userland..." 
> 
> ... or something like that? 

Nope; lockmgr doesn't have that feature, although all the SMPng locking
primitives do, I believe.  In fact, I believe that's the source of
Julian's question, since I've had a conversation with him about adding
that sort of sanity checking.  In adding that sort of sanity checking, you
want to be very sure we don't break any existing assumptions.

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert@fledge.watson.org      Network Associates Laboratories



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