From owner-freebsd-hackers@FreeBSD.ORG  Thu Mar 25 22:45:01 2004
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Date: Fri, 26 Mar 2004 07:44:58 +0100
From: Toni Andjelkovic <toni@soth.at>
To: Sam Lawrance <samuel.lawrance@studentmail.newcastle.edu.au>
Message-ID: <20040326064458.GK1227@tv.soth.at>
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cc: freebsd-hackers@freebsd.org
Subject: Re: kldstat and module ref count
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On Fri, Mar 26 2004 (09:15:26 +1100), Sam Lawrance wrote:
> I've tried to find the answer to this but am stuck. How can I prevent a
> kld module being unloaded if it is still in use?
> 
> Filesystem modules give "device busy" if you try to kldunload them while
> still in use. Any sort of quick pointer in the right direction would be
> much appreciated.

You may veto the unload by returning an error > 0 from the module event
handler. See md_modevent() in sys/dev/md/md.c or vfs_modevent() in
sys/kern/vfs_init.c for examples.

Cheers,
Toni