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Commit 200b916f authored by Cong Wang's avatar Cong Wang Committed by David S. Miller
Browse files

rtnetlink: wait for unregistering devices in rtnl_link_unregister() 



From: Cong Wang <cwang@twopensource.com>

commit 50624c93 (net: Delay default_device_exit_batch until no
devices are unregistering) introduced rtnl_lock_unregistering() for
default_device_exit_batch(). Same race could happen we when rmmod a driver
which calls rtnl_link_unregister() as we call dev->destructor without rtnl
lock.

For long term, I think we should clean up the mess of netdev_run_todo()
and net namespce exit code.

Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: default avatarCong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: default avatarCong Wang <cwang@twopensource.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e84d2f8d

include/linux/rtnetlink.h

+5 −0
Original line number Diff line number Diff line
@@ -4,6 +4,7 @@ 


#include <linux/mutex.h>

#include <linux/netdevice.h>

#include <linux/wait.h>

#include <uapi/linux/rtnetlink.h>



extern int rtnetlink_send(struct sk_buff *skb, struct net *net, u32 pid, u32 group, int echo);
@@ -22,6 +23,10 @@ extern void rtnl_lock(void); 
extern void rtnl_unlock(void);

extern int rtnl_trylock(void);

extern int rtnl_is_locked(void);



extern wait_queue_head_t netdev_unregistering_wq;

extern struct mutex net_mutex;



#ifdef CONFIG_PROVE_LOCKING

extern int lockdep_rtnl_is_held(void);

#else

net/core/dev.c

+1 −1
Original line number Diff line number Diff line
@@ -5541,7 +5541,7 @@ static int dev_new_index(struct net *net) 


/* Delayed registration/unregisteration */

static LIST_HEAD(net_todo_list);

static DECLARE_WAIT_QUEUE_HEAD(netdev_unregistering_wq);

DECLARE_WAIT_QUEUE_HEAD(netdev_unregistering_wq);



static void net_set_todo(struct net_device *dev)

{

net/core/net_namespace.c

+1 −1
Original line number Diff line number Diff line
@@ -24,7 +24,7 @@ 


static LIST_HEAD(pernet_list);

static struct list_head *first_device = &pernet_list;

static DEFINE_MUTEX(net_mutex);

DEFINE_MUTEX(net_mutex);



LIST_HEAD(net_namespace_list);

EXPORT_SYMBOL_GPL(net_namespace_list);

net/core/rtnetlink.c

+32 −1
Original line number Diff line number Diff line
@@ -353,15 +353,46 @@ void __rtnl_link_unregister(struct rtnl_link_ops *ops) 
}

EXPORT_SYMBOL_GPL(__rtnl_link_unregister);



/* Return with the rtnl_lock held when there are no network

 * devices unregistering in any network namespace.

 */

static void rtnl_lock_unregistering_all(void)

{

	struct net *net;

	bool unregistering;

	DEFINE_WAIT(wait);



	for (;;) {

		prepare_to_wait(&netdev_unregistering_wq, &wait,

				TASK_UNINTERRUPTIBLE);

		unregistering = false;

		rtnl_lock();

		for_each_net(net) {

			if (net->dev_unreg_count > 0) {

				unregistering = true;

				break;

			}

		}

		if (!unregistering)

			break;

		__rtnl_unlock();

		schedule();

	}

	finish_wait(&netdev_unregistering_wq, &wait);

}



/**

 * rtnl_link_unregister - Unregister rtnl_link_ops from rtnetlink.

 * @ops: struct rtnl_link_ops * to unregister

 */

void rtnl_link_unregister(struct rtnl_link_ops *ops)

{

	rtnl_lock();

	/* Close the race with cleanup_net() */

	mutex_lock(&net_mutex);

	rtnl_lock_unregistering_all();

	__rtnl_link_unregister(ops);

	rtnl_unlock();

	mutex_unlock(&net_mutex);

}

EXPORT_SYMBOL_GPL(rtnl_link_unregister);