Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754877Ab3JKXSU (ORCPT ); Fri, 11 Oct 2013 19:18:20 -0400 Received: from e9.ny.us.ibm.com ([32.97.182.139]:54739 "EHLO e9.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754227Ab3JKXRp (ORCPT ); Fri, 11 Oct 2013 19:17:45 -0400 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: 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, "Paul E. McKenney" , Stephen Hemminger , "David S. Miller" , bridge@lists.linux-foundation.org, netdev@vger.kernel.org Subject: [PATCH v3 tip/core/rcu 11/14] bridge/br_mdb: Apply ACCESS_ONCE() to avoid sparse false positive Date: Fri, 11 Oct 2013 16:17:28 -0700 Message-Id: <1381533451-29018-11-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.5 In-Reply-To: <1381533451-29018-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20131011231659.GA28062@linux.vnet.ibm.com> <1381533451-29018-1-git-send-email-paulmck@linux.vnet.ibm.com> X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13101123-7182-0000-0000-000008B79079 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1691 Lines: 44 From: "Paul E. McKenney" The sparse checking for rcu_assign_pointer() was recently upgraded to reject non-__kernel address spaces. This also rejects __rcu, which is almost always the right thing to do. However, the use in __br_mdb_del() is legitimate: They are assigning a pointer to an element from an RCU-protected list, and all elements of this list are already visible to caller. This commit therefore silences these false positives by laundering the pointers using ACCESS_ONCE() as suggested by Eric Dumazet and Josh Triplett. Reported-by: kbuild test robot Signed-off-by: Paul E. McKenney Cc: Stephen Hemminger Cc: "David S. Miller" Cc: bridge@lists.linux-foundation.org Cc: netdev@vger.kernel.org --- net/bridge/br_mdb.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/bridge/br_mdb.c b/net/bridge/br_mdb.c index 85a09bb5ca51..de7197ba8695 100644 --- a/net/bridge/br_mdb.c +++ b/net/bridge/br_mdb.c @@ -447,7 +447,7 @@ static int __br_mdb_del(struct net_bridge *br, struct br_mdb_entry *entry) if (p->port->state == BR_STATE_DISABLED) goto unlock; - rcu_assign_pointer(*pp, p->next); + ACCESS_ONCE(*pp) = p->next; /* OK: Both --rcu and visible. */ hlist_del_init(&p->mglist); del_timer(&p->timer); call_rcu_bh(&p->rcu, br_multicast_free_pg); -- 1.8.1.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/