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bonding: remove bond read lock for bond_mii_monitor()

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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 move 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>
This commit is contained in:
dingtianhong 2013-10-24 11:09:03 +08:00 committed by David S. Miller
parent a00f6fcc7d
commit 6b6c526147
1 changed files with 13 additions and 33 deletions
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46
drivers/net/bonding/bond_main.c
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@ -2118,49 +2118,29 @@ 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 (!bond_has_slaves(bond))
if (!rtnl_trylock())
goto re_arm;
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)