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net: Remove net_rwsem from {, un}register_netdevice_notifier() 

These functions take net_rwsem, while wireless_nlevent_flush()
also takes it. But down_read() can't be taken recursive,
because of rw_semaphore design, which prevents it to be occupied
by only readers forever.

Since we take pernet_ops_rwsem in {,un}register_netdevice_notifier(),
net list can't change, so these down_read()/up_read() can be removed.

Fixes: f0b07bb151 "net: Introduce net_rwsem to protect net_namespace_list"
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Kirill Tkhai 2018-03-30 19:38:27 +03:00 committed by David S. Miller
parent c679f6a26d
commit fc1dd36992
1 changed files with 0 additions and 5 deletions
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5
net/core/dev.c
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@ -1633,7 +1633,6 @@ 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);
@ -1647,7 +1646,6 @@ int register_netdevice_notifier(struct notifier_block *nb)
call_netdevice_notifier(nb, NETDEV_UP, dev);
}
}
up_read(&net_rwsem);
unlock:
rtnl_unlock();
@ -1671,7 +1669,6 @@ rollback:
}
outroll:
up_read(&net_rwsem);
raw_notifier_chain_unregister(&netdev_chain, nb);
goto unlock;
}
@ -1704,7 +1701,6 @@ 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) {
@ -1715,7 +1711,6 @@ int unregister_netdevice_notifier(struct notifier_block *nb)
call_netdevice_notifier(nb, NETDEV_UNREGISTER, dev);
}
}
up_read(&net_rwsem);
unlock:
rtnl_unlock();
up_write(&pernet_ops_rwsem);