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Commit 9a0b1e8b authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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net: pktgen: remove rcu locking in pktgen_change_name() 



After Jesper commit back in linux-3.18, we trigger a lockdep
splat in proc_create_data() while allocating memory from
pktgen_change_name().

This patch converts t->if_lock to a mutex, since it is now only
used from control path, and adds proper locking to pktgen_change_name()

1) pktgen_thread_lock to protect the outer loop (iterating threads)
2) t->if_lock to protect the inner loop (iterating devices)

Note that before Jesper patch, pktgen_change_name() was lacking proper
protection, but lockdep was not able to detect the problem.

Fixes: 8788370a ("pktgen: RCU-ify "if_list" to remove lock in next_to_run()")
Reported-by: default avatarJohn Sperbeck <jsperbeck@google.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent a04a480d

net/core/pktgen.c

+10 −7
Original line number Diff line number Diff line
@@ -216,8 +216,8 @@ 
#define M_QUEUE_XMIT		2	/* Inject packet into qdisc */



/* If lock -- protects updating of if_list */

#define   if_lock(t)           spin_lock(&(t->if_lock));

#define   if_unlock(t)           spin_unlock(&(t->if_lock));

#define   if_lock(t)           mutex_lock(&(t->if_lock));

#define   if_unlock(t)           mutex_unlock(&(t->if_lock));



/* Used to help with determining the pkts on receive */

#define PKTGEN_MAGIC 0xbe9be955
@@ -423,7 +423,7 @@ struct pktgen_net { 
};



struct pktgen_thread {

	spinlock_t if_lock;		/* for list of devices */

	struct mutex if_lock;		/* for list of devices */

	struct list_head if_list;	/* All device here */

	struct list_head th_list;

	struct task_struct *tsk;
@@ -2010,11 +2010,13 @@ static void pktgen_change_name(const struct pktgen_net *pn, struct net_device *d 
{

	struct pktgen_thread *t;



	mutex_lock(&pktgen_thread_lock);



	list_for_each_entry(t, &pn->pktgen_threads, th_list) {

		struct pktgen_dev *pkt_dev;



		rcu_read_lock();

		list_for_each_entry_rcu(pkt_dev, &t->if_list, list) {

		if_lock(t);

		list_for_each_entry(pkt_dev, &t->if_list, list) {

			if (pkt_dev->odev != dev)

				continue;
@@ -2029,8 +2031,9 @@ static void pktgen_change_name(const struct pktgen_net *pn, struct net_device *d 
				       dev->name);

			break;

		}

		rcu_read_unlock();

		if_unlock(t);

	}

	mutex_unlock(&pktgen_thread_lock);

}



static int pktgen_device_event(struct notifier_block *unused,
@@ -3762,7 +3765,7 @@ static int __net_init pktgen_create_thread(int cpu, struct pktgen_net *pn) 
		return -ENOMEM;

	}



	spin_lock_init(&t->if_lock);

	mutex_init(&t->if_lock);

	t->cpu = cpu;



	INIT_LIST_HEAD(&t->if_list);