linux-kernel - Re: [PATCH RFC] hlist_add_tail

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Message-ID: <20161205054406-mutt-send-email-mst@kernel.org>
Date:   Mon, 5 Dec 2016 05:47:44 +0200
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     David Miller <davem@...emloft.net>, arnd@...db.de,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] hlist_add_tail_rcu disable sparse warning

On Mon, Nov 28, 2016 at 06:39:19AM -0800, Paul E. McKenney wrote:
> On Fri, Nov 25, 2016 at 07:52:23PM -0500, David Miller wrote:
> > From: "Michael S. Tsirkin" <mst@...hat.com>
> > Date: Wed, 23 Nov 2016 22:48:19 +0200
> > 
> > > I would appreciate review to confirm the function doesn't
> > > do anything unsafe though.
> > > 
> > > In particular, should this use __hlist_for_each_rcu instead?
> > > I note that __hlist_for_each_rcu does rcu_dereference
> > > internally, which is missing here.
> > 
> > I personally think it should use __hlist_for_each_rcu, otherwise
> > nothing expresses the rcu-ness of the operation.
> 
> I like Dave's suggestion.  Michael, does that change work for you?
> 
> 							Thanx, Paul

I think we should change __hlist_for_each_rcu to skip rcu_dereference
though then, since it would be called outside any rcu read size critical
sections here.


-- 
MST