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net: pktgen: remove rcu locking in pktgen_change_name()

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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: 8788370a1d4b ("pktgen: RCU-ify "if_list" to remove lock in next_to_run()")
Reported-by: John Sperbeck <jsperbeck@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2016-10-15 17:50:49 +02:00 committed by David S. Miller
parent a04a480d43
commit 9a0b1e8ba4
1 changed files with 10 additions and 7 deletions
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17
net/core/pktgen.c
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@ -216,8 +216,8 @@
#define M_QUEUE_XMIT 2 /* Inject packet into qdisc */ #define M_QUEUE_XMIT 2 /* Inject packet into qdisc */
/* If lock -- protects updating of if_list */ /* If lock -- protects updating of if_list */
#define if_lock(t) spin_lock(&(t->if_lock)); #define if_lock(t) mutex_lock(&(t->if_lock));
#define if_unlock(t) spin_unlock(&(t->if_lock)); #define if_unlock(t) mutex_unlock(&(t->if_lock));
/* Used to help with determining the pkts on receive */ /* Used to help with determining the pkts on receive */
#define PKTGEN_MAGIC 0xbe9be955 #define PKTGEN_MAGIC 0xbe9be955
@ -423,7 +423,7 @@ struct pktgen_net {
}; };
struct pktgen_thread { 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 if_list; /* All device here */
struct list_head th_list; struct list_head th_list;
struct task_struct *tsk; 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; struct pktgen_thread *t;
mutex_lock(&pktgen_thread_lock);
list_for_each_entry(t, &pn->pktgen_threads, th_list) { list_for_each_entry(t, &pn->pktgen_threads, th_list) {
struct pktgen_dev *pkt_dev; struct pktgen_dev *pkt_dev;
rcu_read_lock(); if_lock(t);
list_for_each_entry_rcu(pkt_dev, &t->if_list, list) { list_for_each_entry(pkt_dev, &t->if_list, list) {
if (pkt_dev->odev != dev) if (pkt_dev->odev != dev)
continue; continue;
@ -2029,8 +2031,9 @@ static void pktgen_change_name(const struct pktgen_net *pn, struct net_device *d
dev->name); dev->name);
break; break;
} }
rcu_read_unlock(); if_unlock(t);
} }
mutex_unlock(&pktgen_thread_lock);
} }
static int pktgen_device_event(struct notifier_block *unused, 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; return -ENOMEM;
} }
spin_lock_init(&t->if_lock); mutex_init(&t->if_lock);
t->cpu = cpu; t->cpu = cpu;
INIT_LIST_HEAD(&t->if_list); INIT_LIST_HEAD(&t->if_list);