From mboxrd@z Thu Jan 1 00:00:00 1970 From: Veaceslav Falico Subject: [PATCH v3 net-next 2/2] bonding: restructure locking of bond_ab_arp_probe() Date: Mon, 27 Jan 2014 14:37:32 +0100 Message-ID: <1390829852-1943-3-git-send-email-vfalico@redhat.com> References: <1390829852-1943-1-git-send-email-vfalico@redhat.com> Cc: Veaceslav Falico , Jay Vosburgh , Andy Gospodarek To: netdev@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:51848 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753473AbaA0Nlw (ORCPT ); Mon, 27 Jan 2014 08:41:52 -0500 In-Reply-To: <1390829852-1943-1-git-send-email-vfalico@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: Currently we're calling it from under RCU context, however we're using some functions that require rtnl to be held. Fix this by restructuring the locking - don't call it under any locks, aquire rcu_read_lock() if we're sending _only_ (i.e. we have the active slave present), and use rtnl locking otherwise - if we need to modify (in)active flags of a slave. CC: Jay Vosburgh CC: Andy Gospodarek Signed-off-by: Veaceslav Falico --- Notes: v2->v3: Use rtnl_trylock(), not to race with queue cancelling. v1->v2: Add two steps - one for sending/rcu, another for modifying/rtnl. drivers/net/bonding/bond_main.c | 57 ++++++++++++++++++++++++++--------------- 1 file changed, 36 insertions(+), 21 deletions(-) diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c index 27e6fdd..dd75615 100644 --- a/drivers/net/bonding/bond_main.c +++ b/drivers/net/bonding/bond_main.c @@ -2599,17 +2599,18 @@ do_failover: /* * Send ARP probes for active-backup mode ARP monitor. - * - * Called with rcu_read_lock hold. */ -static void bond_ab_arp_probe(struct bonding *bond) +static bool bond_ab_arp_probe(struct bonding *bond) { struct slave *slave, *before = NULL, *new_slave = NULL, - *curr_arp_slave = rcu_dereference(bond->current_arp_slave), - *curr_active_slave = rcu_dereference(bond->curr_active_slave); + *curr_arp_slave, *curr_active_slave; struct list_head *iter; bool found = false; + rcu_read_lock(); + curr_arp_slave = rcu_dereference(bond->current_arp_slave); + curr_active_slave = rcu_dereference(bond->curr_active_slave); + if (curr_arp_slave && curr_active_slave) pr_info("PROBE: c_arp %s && cas %s BAD\n", curr_arp_slave->dev->name, @@ -2617,23 +2618,32 @@ static void bond_ab_arp_probe(struct bonding *bond) if (curr_active_slave) { bond_arp_send_all(bond, curr_active_slave); - return; + rcu_read_unlock(); + return true; } + rcu_read_unlock(); /* if we don't have a curr_active_slave, search for the next available * backup slave from the current_arp_slave and make it the candidate * for becoming the curr_active_slave */ + if (!rtnl_trylock()) + return false; + /* curr_arp_slave might have gone away */ + curr_arp_slave = ACCESS_ONCE(bond->current_arp_slave); + if (!curr_arp_slave) { - curr_arp_slave = bond_first_slave_rcu(bond); - if (!curr_arp_slave) - return; + curr_arp_slave = bond_first_slave(bond); + if (!curr_arp_slave) { + rtnl_unlock(); + return true; + } } bond_set_slave_inactive_flags(curr_arp_slave); - bond_for_each_slave_rcu(bond, slave, iter) { + bond_for_each_slave(bond, slave, iter) { if (!found && !before && IS_UP(slave->dev)) before = slave; @@ -2663,21 +2673,26 @@ static void bond_ab_arp_probe(struct bonding *bond) if (!new_slave && before) new_slave = before; - if (!new_slave) - return; + if (!new_slave) { + rtnl_unlock(); + return true; + } new_slave->link = BOND_LINK_BACK; bond_set_slave_active_flags(new_slave); bond_arp_send_all(bond, new_slave); new_slave->jiffies = jiffies; rcu_assign_pointer(bond->current_arp_slave, new_slave); + rtnl_unlock(); + + return true; } static void bond_activebackup_arp_mon(struct work_struct *work) { struct bonding *bond = container_of(work, struct bonding, arp_work.work); - bool should_notify_peers = false; + bool should_notify_peers = false, should_commit = false; int delta_in_ticks; delta_in_ticks = msecs_to_jiffies(bond->params.arp_interval); @@ -2686,12 +2701,11 @@ static void bond_activebackup_arp_mon(struct work_struct *work) goto re_arm; rcu_read_lock(); - should_notify_peers = bond_should_notify_peers(bond); + should_commit = bond_ab_arp_inspect(bond); + rcu_read_unlock(); - if (bond_ab_arp_inspect(bond)) { - rcu_read_unlock(); - + if (should_commit) { /* Race avoidance with bond_close flush of workqueue */ if (!rtnl_trylock()) { delta_in_ticks = 1; @@ -2700,13 +2714,14 @@ static void bond_activebackup_arp_mon(struct work_struct *work) } bond_ab_arp_commit(bond); - rtnl_unlock(); - rcu_read_lock(); } - bond_ab_arp_probe(bond); - rcu_read_unlock(); + if (!bond_ab_arp_probe(bond)) { + /* rtnl locking failed, re-arm */ + delta_in_ticks = 1; + should_notify_peers = false; + } re_arm: if (bond->params.arp_interval) -- 1.8.4