diff options
Diffstat (limited to 'net/core/rtnetlink.c')
| -rw-r--r-- | net/core/rtnetlink.c | 33 |
1 files changed, 33 insertions, 0 deletions
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index 159c9c61e6af..0e4502d641eb 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -95,6 +95,39 @@ void __rtnl_unlock(void) defer_kfree_skb_list = NULL; + /* Ensure that we didn't actually add any TODO item when __rtnl_unlock() + * is used. In some places, e.g. in cfg80211, we have code that will do + * something like + * rtnl_lock() + * wiphy_lock() + * ... + * rtnl_unlock() + * + * and because netdev_run_todo() acquires the RTNL for items on the list + * we could cause a situation such as this: + * Thread 1 Thread 2 + * rtnl_lock() + * unregister_netdevice() + * __rtnl_unlock() + * rtnl_lock() + * wiphy_lock() + * rtnl_unlock() + * netdev_run_todo() + * __rtnl_unlock() + * + * // list not empty now + * // because of thread 2 + * rtnl_lock() + * while (!list_empty(...)) + * rtnl_lock() + * wiphy_lock() + * **** DEADLOCK **** + * + * However, usage of __rtnl_unlock() is rare, and so we can ensure that + * it's not used in cases where something is added to do the list. + */ + WARN_ON(!list_empty(&net_todo_list)); + mutex_unlock(&rtnl_mutex); while (head) { |