linux-kernel - Re: [PATCH 2/2] auth_gss: unregister gss

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Date:	Mon, 30 Oct 2006 23:54:04 +0900
From:	Akinobu Mita <akinobu.mita@...il.com>
To:	Trond Myklebust <Trond.Myklebust@...app.com>
Cc:	linux-kernel@...r.kernel.org, Andy Adamson <andros@...i.umich.edu>,
	"J. Bruce Fields" <bfields@...i.umich.edu>,
	Olaf Kirch <okir@...ad.swb.de>
Subject: Re: [PATCH 2/2] auth_gss: unregister gss_domain when unloading module

On Sun, Oct 29, 2006 at 03:15:59PM -0500, Trond Myklebust wrote:

> > +void svcauth_gss_unregister_pseudoflavor(char *name)
> > +{
> > +	struct auth_domain *dom;
> > +
> > +	dom = auth_domain_find(name);
> > +	if (dom) {
> > +		auth_domain_put(dom);
> > +		auth_domain_put(dom);
> > +	}
> > +}
> 
> Strictly speaking, if you want to be smp-safe, you probably need
> something like the following:
> 
> 	dom = auth_domain_find(name);
> 	if (dom) {
> 		spin_lock(&auth_domain_lock);
> 		if (!hlist_unhashed(dom->hash)) {
> 			hlist_del_init(dom->hash);
> 			spin_unlock(&auth_domain_lock);
> 			auth_domain_put(dom);
> 		} else
> 			spin_unlock(&auth_domain_lock);
> 		auth_domain_put(dom);
> 	}
> 
> and then add a test for hlist_unhashed into auth_domain_put(). If not,
> some other processor could race you inside
> svcauth_gss_unregister_pseudoflavor.

But auth_domain_table is protected by auth_domain_lock while we are
using auth_domain_put()/auth_domain_lookup()/auth_domain_find().
So I think there is not big difference.
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