From mboxrd@z Thu Jan 1 00:00:00 1970 From: Veaceslav Falico Subject: [PATCH v4 net-next 2/3] bonding: fix __get_first_agg RCU usage Date: Fri, 10 Jan 2014 11:59:44 +0100 Message-ID: <1389351585-19615-3-git-send-email-vfalico@redhat.com> References: <1389351585-19615-1-git-send-email-vfalico@redhat.com> Cc: Veaceslav Falico , dingtianhong@huawei.com, Jay Vosburgh , Andy Gospodarek To: netdev@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:34611 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756705AbaAJLEE (ORCPT ); Fri, 10 Jan 2014 06:04:04 -0500 In-Reply-To: <1389351585-19615-1-git-send-email-vfalico@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: Currently, the RCU read lock usage is just wrong - it gets the slave struct under RCU and continues to use it when RCU lock is released. However, it's still safe to do this cause we didn't need the rcu_read_lock() initially - all of the __get_first_agg() callers are either holding RCU read lock or the RTNL lock, so that we can't sync while in it. Fixes: be79bd048 ("bonding: add RCU for bond_3ad_state_machine_handler()") CC: dingtianhong@huawei.com CC: Jay Vosburgh CC: Andy Gospodarek Signed-off-by: Veaceslav Falico --- Notes: v3 -> v4: add rcu_read_lock() to silence lockdep. v2 -> v3: Use the rcu primitives. v1 -> v2: Don't use RCU primitives as we can hold RTNL. drivers/net/bonding/bond_3ad.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c index da0d7c5..b49f421 100644 --- a/drivers/net/bonding/bond_3ad.c +++ b/drivers/net/bonding/bond_3ad.c @@ -143,11 +143,13 @@ static inline struct bonding *__get_bond_by_port(struct port *port) * * Return the aggregator of the first slave in @bond, or %NULL if it can't be * found. + * The caller must hold RCU or RTNL lock. */ static inline struct aggregator *__get_first_agg(struct port *port) { struct bonding *bond = __get_bond_by_port(port); struct slave *first_slave; + struct aggregator *agg; /* If there's no bond for this port, or bond has no slaves */ if (bond == NULL) @@ -155,9 +157,10 @@ static inline struct aggregator *__get_first_agg(struct port *port) rcu_read_lock(); first_slave = bond_first_slave_rcu(bond); + agg = first_slave ? &(SLAVE_AD_INFO(first_slave).aggregator) : NULL; rcu_read_unlock(); - return first_slave ? &(SLAVE_AD_INFO(first_slave).aggregator) : NULL; + return agg; } /** -- 1.8.4