Commit fd888e85 authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by David S. Miller
Browse files

net: Write lock dev_base_lock without disabling bottom halves. 



The writer acquires dev_base_lock with disabled bottom halves.
The reader can acquire dev_base_lock without disabling bottom halves
because there is no writer in softirq context.

On PREEMPT_RT the softirqs are preemptible and local_bh_disable() acts
as a lock to ensure that resources, that are protected by disabling
bottom halves, remain protected.
This leads to a circular locking dependency if the lock acquired with
disabled bottom halves (as in write_lock_bh()) and somewhere else with
enabled bottom halves (as by read_lock() in netstat_show()) followed by
disabling bottom halves (cxgb_get_stats() -> t4_wr_mbox_meat_timeout()
-> spin_lock_bh()). This is the reverse locking order.

All read_lock() invocation are from sysfs callback which are not invoked
from softirq context. Therefore there is no need to disable bottom
halves while acquiring a write lock.

Acquire the write lock of dev_base_lock without disabling bottom halves.

Reported-by: default avatarPei Zhang <pezhang@redhat.com>
Reported-by: default avatarLuis Claudio R. Goncalves <lgoncalv@redhat.com>
Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 07b8ca37

net/core/dev.c

+8 −8
Original line number Diff line number Diff line
@@ -365,12 +365,12 @@ static void list_netdevice(struct net_device *dev) 


	ASSERT_RTNL();



	write_lock_bh(&dev_base_lock);

	write_lock(&dev_base_lock);

	list_add_tail_rcu(&dev->dev_list, &net->dev_base_head);

	netdev_name_node_add(net, dev->name_node);

	hlist_add_head_rcu(&dev->index_hlist,

			   dev_index_hash(net, dev->ifindex));

	write_unlock_bh(&dev_base_lock);

	write_unlock(&dev_base_lock);



	dev_base_seq_inc(net);

}
@@ -383,11 +383,11 @@ static void unlist_netdevice(struct net_device *dev) 
	ASSERT_RTNL();



	/* Unlink dev from the device chain */

	write_lock_bh(&dev_base_lock);

	write_lock(&dev_base_lock);

	list_del_rcu(&dev->dev_list);

	netdev_name_node_del(dev->name_node);

	hlist_del_rcu(&dev->index_hlist);

	write_unlock_bh(&dev_base_lock);

	write_unlock(&dev_base_lock);



	dev_base_seq_inc(dev_net(dev));

}
@@ -1188,15 +1188,15 @@ int dev_change_name(struct net_device *dev, const char *newname) 


	netdev_adjacent_rename_links(dev, oldname);



	write_lock_bh(&dev_base_lock);

	write_lock(&dev_base_lock);

	netdev_name_node_del(dev->name_node);

	write_unlock_bh(&dev_base_lock);

	write_unlock(&dev_base_lock);



	synchronize_rcu();



	write_lock_bh(&dev_base_lock);

	write_lock(&dev_base_lock);

	netdev_name_node_add(net, dev->name_node);

	write_unlock_bh(&dev_base_lock);

	write_unlock(&dev_base_lock);



	ret = call_netdevice_notifiers(NETDEV_CHANGENAME, dev);

	ret = notifier_to_errno(ret);

net/core/link_watch.c

+2 −2
Original line number Diff line number Diff line
@@ -55,7 +55,7 @@ static void rfc2863_policy(struct net_device *dev) 
	if (operstate == dev->operstate)

		return;



	write_lock_bh(&dev_base_lock);

	write_lock(&dev_base_lock);



	switch(dev->link_mode) {

	case IF_LINK_MODE_TESTING:
@@ -74,7 +74,7 @@ static void rfc2863_policy(struct net_device *dev) 


	dev->operstate = operstate;



	write_unlock_bh(&dev_base_lock);

	write_unlock(&dev_base_lock);

}

net/core/rtnetlink.c

+4 −4
Original line number Diff line number Diff line
@@ -842,9 +842,9 @@ static void set_operstate(struct net_device *dev, unsigned char transition) 
	}



	if (dev->operstate != operstate) {

		write_lock_bh(&dev_base_lock);

		write_lock(&dev_base_lock);

		dev->operstate = operstate;

		write_unlock_bh(&dev_base_lock);

		write_unlock(&dev_base_lock);

		netdev_state_change(dev);

	}

}
@@ -2778,11 +2778,11 @@ static int do_setlink(const struct sk_buff *skb, 
	if (tb[IFLA_LINKMODE]) {

		unsigned char value = nla_get_u8(tb[IFLA_LINKMODE]);



		write_lock_bh(&dev_base_lock);

		write_lock(&dev_base_lock);

		if (dev->link_mode ^ value)

			status |= DO_SETLINK_NOTIFY;

		dev->link_mode = value;

		write_unlock_bh(&dev_base_lock);

		write_unlock(&dev_base_lock);

	}



	if (tb[IFLA_VFINFO_LIST]) {

net/hsr/hsr_device.c

+3 −3
Original line number Diff line number Diff line
@@ -30,13 +30,13 @@ static bool is_slave_up(struct net_device *dev) 


static void __hsr_set_operstate(struct net_device *dev, int transition)

{

	write_lock_bh(&dev_base_lock);

	write_lock(&dev_base_lock);

	if (dev->operstate != transition) {

		dev->operstate = transition;

		write_unlock_bh(&dev_base_lock);

		write_unlock(&dev_base_lock);

		netdev_state_change(dev);

	} else {

		write_unlock_bh(&dev_base_lock);

		write_unlock(&dev_base_lock);

	}

}