From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ding Tianhong Subject: [PATCH net-next v2 1/5] bonding: remove bond read lock for bond_mii_monitor() Date: Thu, 24 Oct 2013 11:09:03 +0800 Message-ID: <52688F4F.2080204@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit To: Jay Vosburgh , Andy Gospodarek , "David S. Miller" , Nikolay Aleksandrov , Veaceslav Falico , Netdev Return-path: Received: from szxga01-in.huawei.com ([119.145.14.64]:6024 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753041Ab3JXDJb (ORCPT ); Wed, 23 Oct 2013 23:09:31 -0400 Sender: netdev-owner@vger.kernel.org List-ID: The bond slave list may change when the monitor is running, the slave list is no longer protected by bond->lock, only protected by rtnl lock(), so we has 3 way to modify it: 1.add bond_master_upper_dev_link() and bond_upper_dev_unlink() in bond->lock, but it is unsafe to call call_netdevice_notifiers() in write lock. 2.remove unused bond->lock for monitor function, only use the exist rtnl lock(). 3.use rcu_read_lock() to protect it, of course, it will transform bond_for_each_slave to bond_for_each_slave_rcu() and performance is better, but in slow path, it is ignored. so I remove the bond->lock and move the rtnl lock to protect the whole monitor function. Signed-off-by: Ding Tianhong --- drivers/net/bonding/bond_main.c | 44 +++++++++++------------------------------ 1 file changed, 12 insertions(+), 32 deletions(-) diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c index d90734f..ba90f45 100644 --- a/drivers/net/bonding/bond_main.c +++ b/drivers/net/bonding/bond_main.c @@ -2155,49 +2155,29 @@ void bond_mii_monitor(struct work_struct *work) struct bonding *bond = container_of(work, struct bonding, mii_work.work); bool should_notify_peers = false; - unsigned long delay; - read_lock(&bond->lock); - - delay = msecs_to_jiffies(bond->params.miimon); + if (!rtnl_trylock()) + goto re_arm; - if (!bond_has_slaves(bond)) + if (!bond_has_slaves(bond)) { + rtnl_unlock(); goto re_arm; + } should_notify_peers = bond_should_notify_peers(bond); - if (bond_miimon_inspect(bond)) { - read_unlock(&bond->lock); - - /* Race avoidance with bond_close cancel of workqueue */ - if (!rtnl_trylock()) { - read_lock(&bond->lock); - delay = 1; - should_notify_peers = false; - goto re_arm; - } - - read_lock(&bond->lock); - + if (bond_miimon_inspect(bond)) bond_miimon_commit(bond); - read_unlock(&bond->lock); - rtnl_unlock(); /* might sleep, hold no other locks */ - read_lock(&bond->lock); - } + if (should_notify_peers) + call_netdevice_notifiers(NETDEV_NOTIFY_PEERS, bond->dev); + + rtnl_unlock(); re_arm: if (bond->params.miimon) - queue_delayed_work(bond->wq, &bond->mii_work, delay); - - read_unlock(&bond->lock); - - if (should_notify_peers) { - if (!rtnl_trylock()) - return; - call_netdevice_notifiers(NETDEV_NOTIFY_PEERS, bond->dev); - rtnl_unlock(); - } + queue_delayed_work(bond->wq, &bond->mii_work, + msecs_to_jiffies(bond->params.miimon)); } static bool bond_has_this_ip(struct bonding *bond, __be32 ip) -- 1.8.2.1