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authordingtianhong <dingtianhong@huawei.com>2013-12-13 10:19:39 +0800
committerDavid S. Miller <davem@davemloft.net>2013-12-14 01:58:01 -0500
commit4cb4f97b7e361745281e843499ba58691112d2f8 (patch)
treeeb247661d99b945c070eb5ddd1875341d5b78446
parentb2e7aceb00b2621431e220748f7158b131b89e7b (diff)
downloadop-kernel-dev-4cb4f97b7e361745281e843499ba58691112d2f8.zip
op-kernel-dev-4cb4f97b7e361745281e843499ba58691112d2f8.tar.gz
bonding: rebuild the lock use for bond_mii_monitor()
The bond_mii_monitor() still use bond lock to protect bond slave list, it is no effect, I have 2 way to fix the problem, move the RTNL to the top of the function, or add RCU to protect the bond slave list, according to the Jay Vosburgh's opinion, 10 times one second is a truely big performance loss if use RTNL to protect the whole monitor, so I would take the advice and use RCU to protect the bond slave list. The bond_has_slave() will not protect by anything, there will no things happen if the slave list is be changed, unless the bond was free, but it will not happened before the monitor, the bond will closed before be freed. The peers notify for the bond will calling curr_active_slave, so derefence the slave to make sure we will accessing the same slave if the curr_active_slave changed, as the rcu dereference need in read-side critical sector and bond_change_active_slave() will call it with no RCU hold, so add peer notify in rcu_read_lock which will be nested in monitor. Suggested-by: Jay Vosburgh <fubar@us.ibm.com> Suggested-by: Veaceslav Falico <vfalico@redhat.com> Signed-off-by: Ding Tianhong <dingtianhong@huawei.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--drivers/net/bonding/bond_main.c24
1 files changed, 11 insertions, 13 deletions
diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 04ae426..b34634a 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -815,7 +815,11 @@ static struct slave *bond_find_best_slave(struct bonding *bond)
static bool bond_should_notify_peers(struct bonding *bond)
{
- struct slave *slave = bond->curr_active_slave;
+ struct slave *slave;
+
+ rcu_read_lock();
+ slave = rcu_dereference(bond->curr_active_slave);
+ rcu_read_unlock();
pr_debug("bond_should_notify_peers: bond %s slave %s\n",
bond->dev->name, slave ? slave->dev->name : "NULL");
@@ -1919,7 +1923,7 @@ static int bond_miimon_inspect(struct bonding *bond)
ignore_updelay = !bond->curr_active_slave ? true : false;
- bond_for_each_slave(bond, slave, iter) {
+ bond_for_each_slave_rcu(bond, slave, iter) {
slave->new_link = BOND_LINK_NOCHANGE;
link_state = bond_check_dev_link(bond, slave->dev, 0);
@@ -2117,41 +2121,35 @@ void bond_mii_monitor(struct work_struct *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))
goto re_arm;
+ rcu_read_lock();
+
should_notify_peers = bond_should_notify_peers(bond);
if (bond_miimon_inspect(bond)) {
- read_unlock(&bond->lock);
+ rcu_read_unlock();
/* 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);
-
bond_miimon_commit(bond);
- read_unlock(&bond->lock);
rtnl_unlock(); /* might sleep, hold no other locks */
- read_lock(&bond->lock);
- }
+ } else
+ rcu_read_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;
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