Commit 7f1bb571 authored Oct 24, 2013 by dingtianhong Committed by David S. Miller Oct 27, 2013

bonding: remove bond read lock for bond_loadbalance_arp_mon()

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 have 3 ways 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 existing 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 add the rtnl lock to protect the whole monitor function.

Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 2d0dafb0

drivers/net/bonding/bond_main.c

+6 −4

Original line number	Diff line number	Diff line
		@@ -2396,10 +2396,13 @@ void bond_loadbalance_arp_mon(struct work_struct *work)
		struct list_head *iter;
		int do_failover = 0;

		read_lock(&bond->lock);
		if (!rtnl_trylock())
		goto re_arm;

		if (!bond_has_slaves(bond))
		if (!bond_has_slaves(bond)) {
		rtnl_unlock();
		goto re_arm;
		}

		oldcurrent = bond->curr_active_slave;
		/* see if any of the previous devices are up now (i.e. they have
		@@ -2481,13 +2484,12 @@ void bond_loadbalance_arp_mon(struct work_struct *work)
		write_unlock_bh(&bond->curr_slave_lock);
		unblock_netpoll_tx();
		}
		rtnl_unlock();

		re_arm:
		if (bond->params.arp_interval)
		queue_delayed_work(bond->wq, &bond->arp_work,
		msecs_to_jiffies(bond->params.arp_interval));

		read_unlock(&bond->lock);
		}

		/*