From eb9fa4b0199f62df3d174d32b4bd534df8ba4533 Mon Sep 17 00:00:00 2001 From: dingtianhong Date: Fri, 13 Dec 2013 10:20:02 +0800 Subject: [PATCH] bonding: rebuild the lock use for bond_activebackup_arp_mon() The bond_activebackup_arp_mon() use the bond lock for read to protect the slave list, it is no effect, and the RTNL is only called for bond_ab_arp_commit() and peer notify, for the performance better, use RCU to replace with the bond lock, to the bond slave list need to called in RCU, add a new bond_first_slave_rcu() to get the first slave in RCU protection. In bond_ab_arp_probe(), the bond->current_arp_slave may changd if bond release slave, just like: bond_ab_arp_probe() bond_release() cpu 0 cpu 1 ... if (bond->current_arp_slave...) ... ... bond->current_arp_slave = NULl bond->current_arp_slave->dev->name ... So the current_arp_slave need to dereference in the section. Suggested-by: Nikolay Aleksandrov Suggested-by: Jay Vosburgh Suggested-by: Veaceslav Falico Signed-off-by: Ding Tianhong Signed-off-by: David S. Miller --- drivers/net/bonding/bond_main.c | 45 +++++++++++++++------------------ 1 file changed, 20 insertions(+), 25 deletions(-) diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c index 1781ea620d76..bad1bf949546 100644 --- a/drivers/net/bonding/bond_main.c +++ b/drivers/net/bonding/bond_main.c @@ -2517,7 +2517,7 @@ re_arm: * place for the slave. Returns 0 if no changes are found, >0 if changes * to link states must be committed. * - * Called with bond->lock held for read. + * Called with rcu_read_lock hold. */ static int bond_ab_arp_inspect(struct bonding *bond) { @@ -2526,7 +2526,7 @@ static int bond_ab_arp_inspect(struct bonding *bond) struct slave *slave; int commit = 0; - bond_for_each_slave(bond, slave, iter) { + bond_for_each_slave_rcu(bond, slave, iter) { slave->new_link = BOND_LINK_NOCHANGE; last_rx = slave_last_rx(bond, slave); @@ -2588,7 +2588,7 @@ static int bond_ab_arp_inspect(struct bonding *bond) * Called to commit link state changes noted by inspection step of * active-backup mode ARP monitor. * - * Called with RTNL and bond->lock for read. + * Called with RTNL hold. */ static void bond_ab_arp_commit(struct bonding *bond) { @@ -2663,19 +2663,20 @@ do_failover: /* * Send ARP probes for active-backup mode ARP monitor. * - * Called with bond->lock held for read. + * Called with rcu_read_lock hold. */ static void bond_ab_arp_probe(struct bonding *bond) { - struct slave *slave, *before = NULL, *new_slave = NULL; + struct slave *slave, *before = NULL, *new_slave = NULL, + *curr_arp_slave = rcu_dereference(bond->current_arp_slave); struct list_head *iter; bool found = false; read_lock(&bond->curr_slave_lock); - if (bond->current_arp_slave && bond->curr_active_slave) + if (curr_arp_slave && bond->curr_active_slave) pr_info("PROBE: c_arp %s && cas %s BAD\n", - bond->current_arp_slave->dev->name, + curr_arp_slave->dev->name, bond->curr_active_slave->dev->name); if (bond->curr_active_slave) { @@ -2691,15 +2692,15 @@ static void bond_ab_arp_probe(struct bonding *bond) * for becoming the curr_active_slave */ - if (!bond->current_arp_slave) { - bond->current_arp_slave = bond_first_slave(bond); - if (!bond->current_arp_slave) + if (!curr_arp_slave) { + curr_arp_slave = bond_first_slave_rcu(bond); + if (!curr_arp_slave) return; } - bond_set_slave_inactive_flags(bond->current_arp_slave); + bond_set_slave_inactive_flags(curr_arp_slave); - bond_for_each_slave(bond, slave, iter) { + bond_for_each_slave_rcu(bond, slave, iter) { if (!found && !before && IS_UP(slave->dev)) before = slave; @@ -2722,7 +2723,7 @@ static void bond_ab_arp_probe(struct bonding *bond) pr_info("%s: backup interface %s is now down.\n", bond->dev->name, slave->dev->name); } - if (slave == bond->current_arp_slave) + if (slave == curr_arp_slave) found = true; } @@ -2736,8 +2737,7 @@ static void bond_ab_arp_probe(struct bonding *bond) bond_set_slave_active_flags(new_slave); bond_arp_send_all(bond, new_slave); new_slave->jiffies = jiffies; - bond->current_arp_slave = new_slave; - + rcu_assign_pointer(bond->current_arp_slave, new_slave); } void bond_activebackup_arp_mon(struct work_struct *work) @@ -2747,43 +2747,38 @@ void bond_activebackup_arp_mon(struct work_struct *work) bool should_notify_peers = false; int delta_in_ticks; - read_lock(&bond->lock); - delta_in_ticks = msecs_to_jiffies(bond->params.arp_interval); if (!bond_has_slaves(bond)) goto re_arm; + rcu_read_lock(); + should_notify_peers = bond_should_notify_peers(bond); if (bond_ab_arp_inspect(bond)) { - read_unlock(&bond->lock); + rcu_read_unlock(); /* Race avoidance with bond_close flush of workqueue */ if (!rtnl_trylock()) { - read_lock(&bond->lock); delta_in_ticks = 1; should_notify_peers = false; goto re_arm; } - read_lock(&bond->lock); - bond_ab_arp_commit(bond); - read_unlock(&bond->lock); rtnl_unlock(); - read_lock(&bond->lock); + rcu_read_lock(); } bond_ab_arp_probe(bond); + rcu_read_unlock(); re_arm: if (bond->params.arp_interval) queue_delayed_work(bond->wq, &bond->arp_work, delta_in_ticks); - read_unlock(&bond->lock); - if (should_notify_peers) { if (!rtnl_trylock()) return;