From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
laijs@cn.fujitsu.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de,
peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com,
edumazet@google.com, darren@dvhart.com, fweisbec@gmail.com,
sbw@mit.edu, "David S. Miller" <davem@davemloft.net>,
Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
James Morris <jmorris@namei.org>,
Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
Patrick McHardy <kaber@trash.net>,
netdev@vger.kernel.org
Subject: Re: [PATCH v2 tip/core/rcu 07/13] ipv6/ip6_tunnel: Apply rcu_access_pointer() to avoid sparse false positive
Date: Wed, 9 Oct 2013 15:36:52 -0700 [thread overview]
Message-ID: <20131009223652.GC5790@linux.vnet.ibm.com> (raw)
In-Reply-To: <1381356624.4971.26.camel@edumazet-glaptop.roam.corp.google.com>
On Wed, Oct 09, 2013 at 03:10:24PM -0700, Eric Dumazet wrote:
> On Wed, 2013-10-09 at 14:57 -0700, Paul E. McKenney wrote:
>
> > Hmmm... I could use RCU_INIT_POINTER(). Something like the following?
> >
> > RCU_INIT_POINTER(ACCESS_ONCE(*tp), t->next);
> >
> > The ACCESS_ONCE() to prevent the compiler from doing anything stupid.
> > Presumably the value of t->next cannot change, so a normal load suffices.
> >
> > Or did you have something else in mind?
>
> Well, *tp and t->next are both of the same type, with __rcu attribute.
>
> struct ip6_tnl __rcu **tp;
>
> So I meant :
>
> ACCESS_ONCE(*tp) = t->next;
>
> If really we can have a really stupid compiler.
That would work, though it would probably give sparse complaints.
Of course, it is not the stupid compilers that worry me, but rather the
smart ones...
Thanx, Paul
next prev parent reply other threads:[~2013-10-09 22:36 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-09 21:29 [PATCH v2 tip/core/rcu 0/13] Sparse-related updates for 3.13 Paul E. McKenney
[not found] ` <1381354186-16285-1-git-send-email-paulmck@linux.vnet.ibm.com>
2013-10-09 21:29 ` [PATCH v2 tip/core/rcu 03/13] bridge: Apply rcu_access_pointer() to avoid sparse false positive Paul E. McKenney
2013-10-09 21:29 ` [PATCH v2 tip/core/rcu 04/13] wireless: " Paul E. McKenney
2013-10-09 21:29 ` [PATCH v2 tip/core/rcu 05/13] decnet: " Paul E. McKenney
2013-10-09 22:28 ` Josh Triplett
2013-10-09 22:46 ` Paul E. McKenney
2013-10-09 22:57 ` Josh Triplett
2013-10-09 23:57 ` Paul E. McKenney
2013-10-09 22:58 ` Dhaval Giani
2013-10-09 23:54 ` Paul E. McKenney
2013-10-09 21:29 ` [PATCH v2 tip/core/rcu 06/13] ipv4/ip_socketglue: " Paul E. McKenney
2013-10-09 21:29 ` [PATCH v2 tip/core/rcu 07/13] ipv6/ip6_tunnel: " Paul E. McKenney
2013-10-09 21:42 ` Eric Dumazet
2013-10-09 21:57 ` Paul E. McKenney
2013-10-09 22:10 ` Eric Dumazet
2013-10-09 22:36 ` Paul E. McKenney [this message]
2013-10-09 22:51 ` Eric Dumazet
2013-10-09 22:56 ` Josh Triplett
2013-10-09 23:17 ` Eric Dumazet
2013-10-09 23:40 ` Josh Triplett
2013-10-10 0:12 ` Eric Dumazet
2013-10-10 0:28 ` Paul E. McKenney
2013-10-10 2:04 ` Hannes Frederic Sowa
2013-10-10 19:05 ` Paul E. McKenney
2013-10-12 2:25 ` Hannes Frederic Sowa
2013-10-12 7:53 ` Paul E. McKenney
2013-10-12 16:43 ` Hannes Frederic Sowa
2013-10-12 17:37 ` Hannes Frederic Sowa
2013-10-12 19:42 ` Mathieu Desnoyers
2013-10-13 11:14 ` Paul E. McKenney
2013-10-13 20:11 ` Hannes Frederic Sowa
2013-10-11 0:20 ` Josh Triplett
2013-10-11 13:25 ` Paul E. McKenney
2013-10-09 21:29 ` [PATCH v2 tip/core/rcu 08/13] ipv6/ip6_gre: " Paul E. McKenney
2013-10-09 21:29 ` [PATCH v2 tip/core/rcu 09/13] ipv6/sit: " Paul E. McKenney
2013-10-09 21:29 ` [PATCH v2 tip/core/rcu 10/13] mac80211: " Paul E. McKenney
2013-10-09 21:29 ` [PATCH v2 tip/core/rcu 11/13] bridge/br_mdb: " Paul E. McKenney
2013-10-09 21:29 ` [PATCH v2 tip/core/rcu 12/13] bonding/bond_main: " Paul E. McKenney
2013-10-09 21:29 ` [PATCH v2 tip/core/rcu 13/13] bonding/bond_alb.c: " Paul E. McKenney
2013-10-09 22:18 ` [PATCH v2 tip/core/rcu 0/13] Sparse-related updates for 3.13 Josh Triplett
2013-10-09 22:46 ` Paul E. McKenney
2013-10-09 22:23 ` Josh Triplett
2013-10-09 22:30 ` Josh Triplett
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