bonding: remove bond read lock for bond_mii_monitor()
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>
diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index a141f40..0a7e325 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -2118,49 +2118,29 @@
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)