diff options
| author | Kirill Tkhai <ktkhai@virtuozzo.com> | 2018-03-29 19:20:32 +0300 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-03-29 13:47:53 -0400 |
| commit | f0b07bb151b098d291fd1fd71ef7a2df56fb124a (patch) | |
| tree | 24f28ec5ec61e4b0950fef35da79853357a34afb /net/core/dev.c | |
| parent | 906edee91e79af5a348f1ad1b3f9b4b948db3db7 (diff) | |
net: Introduce net_rwsem to protect net_namespace_list
rtnl_lock() is used everywhere, and contention is very high.
When someone wants to iterate over alive net namespaces,
he/she has no a possibility to do that without exclusive lock.
But the exclusive rtnl_lock() in such places is overkill,
and it just increases the contention. Yes, there is already
for_each_net_rcu() in kernel, but it requires rcu_read_lock(),
and this can't be sleepable. Also, sometimes it may be need
really prevent net_namespace_list growth, so for_each_net_rcu()
is not fit there.
This patch introduces new rw_semaphore, which will be used
instead of rtnl_mutex to protect net_namespace_list. It is
sleepable and allows not-exclusive iterations over net
namespaces list. It allows to stop using rtnl_lock()
in several places (what is made in next patches) and makes
less the time, we keep rtnl_mutex. Here we just add new lock,
while the explanation of we can remove rtnl_lock() there are
in next patches.
Fine grained locks generally are better, then one big lock,
so let's do that with net_namespace_list, while the situation
allows that.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core/dev.c')
| -rw-r--r-- | net/core/dev.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/net/core/dev.c b/net/core/dev.c index e13807b5c84d..eca5458b2753 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -1629,6 +1629,7 @@ int register_netdevice_notifier(struct notifier_block *nb) goto unlock; if (dev_boot_phase) goto unlock; + down_read(&net_rwsem); for_each_net(net) { for_each_netdev(net, dev) { err = call_netdevice_notifier(nb, NETDEV_REGISTER, dev); @@ -1642,6 +1643,7 @@ int register_netdevice_notifier(struct notifier_block *nb) call_netdevice_notifier(nb, NETDEV_UP, dev); } } + up_read(&net_rwsem); unlock: rtnl_unlock(); @@ -1664,6 +1666,7 @@ rollback: } outroll: + up_read(&net_rwsem); raw_notifier_chain_unregister(&netdev_chain, nb); goto unlock; } @@ -1694,6 +1697,7 @@ int unregister_netdevice_notifier(struct notifier_block *nb) if (err) goto unlock; + down_read(&net_rwsem); for_each_net(net) { for_each_netdev(net, dev) { if (dev->flags & IFF_UP) { @@ -1704,6 +1708,7 @@ int unregister_netdevice_notifier(struct notifier_block *nb) call_netdevice_notifier(nb, NETDEV_UNREGISTER, dev); } } + up_read(&net_rwsem); unlock: rtnl_unlock(); return err; |