From: Steven Rostedt <rostedt@goodmis.org>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
linux-kernel@vger.kernel.org,
Josh Triplett <josh@joshtriplett.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
David Miller <davem@davemloft.net>
Subject: Re: [PATCH] hlist_add_tail_rcu disable sparse warning
Date: Wed, 26 Apr 2017 09:13:43 -0400 [thread overview]
Message-ID: <20170426091343.073af471@gandalf.local.home> (raw)
In-Reply-To: <20170227202547-mutt-send-email-mst@kernel.org>
Paul,
Did you see this email?
-- Steve
On Mon, 27 Feb 2017 20:26:01 +0200
"Michael S. Tsirkin" <mst@redhat.com> wrote:
> On Fri, Feb 10, 2017 at 07:39:49PM +0200, Michael S. Tsirkin wrote:
> > sparse is unhappy about this code in hlist_add_tail_rcu:
> >
> > struct hlist_node *i, *last = NULL;
> >
> > for (i = hlist_first_rcu(h); i; i = hlist_next_rcu(i))
> > last = i;
> >
> > This is because hlist_next_rcu and hlist_next_rcu return
> > __rcu pointers.
> >
> > It's a false positive - it's a write side primitive and so
> > does not need to be called in a read side critical section.
> >
> > The following trivial patch disables the warning
> > without changing the behaviour in any way.
> >
> > Note: __hlist_for_each_rcu would also remove the warning but it would be
> > confusing since it calls rcu_derefence and is designed to run in the rcu
> > read side critical section.
> >
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
>
> ping
>
> > changes since RFC
> > added commit log text to explain why don't we use __hlist_for_each_rcu
> >
> > include/linux/rculist.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/include/linux/rculist.h b/include/linux/rculist.h
> > index 4f7a956..bf578e8 100644
> > --- a/include/linux/rculist.h
> > +++ b/include/linux/rculist.h
> > @@ -509,7 +509,7 @@ static inline void hlist_add_tail_rcu(struct hlist_node *n,
> > {
> > struct hlist_node *i, *last = NULL;
> >
> > - for (i = hlist_first_rcu(h); i; i = hlist_next_rcu(i))
> > + for (i = h->first; i; i = i->next)
> > last = i;
> >
> > if (last) {
> > --
> > MST
next prev parent reply other threads:[~2017-04-26 13:15 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-10 17:39 [PATCH] hlist_add_tail_rcu disable sparse warning Michael S. Tsirkin
2017-02-27 18:26 ` Michael S. Tsirkin
2017-04-26 13:13 ` Steven Rostedt [this message]
2017-04-26 14:02 ` Paul E. McKenney
2017-02-27 18:40 ` Steven Rostedt
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