AcoSail/kernel_optimize_test
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bonding: remove bond read lock for bond_loadbalance_arp_mon()

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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 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>
This commit is contained in:
dingtianhong 2013-10-24 11:09:17 +08:00 committed by David S. Miller
parent 2d0dafb015
commit 7f1bb571b7
1 changed files with 7 additions and 5 deletions
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12
drivers/net/bonding/bond_main.c
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@ -2396,11 +2396,14 @@ void bond_loadbalance_arp_mon(struct work_struct *work)
struct list_head *iter;
int do_failover = 0;
read_lock(&bond->lock);
if (!bond_has_slaves(bond))
if (!rtnl_trylock())
goto re_arm;
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
* xmt and rcv traffic). the curr_active_slave does not come into
@ -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);
}
/*