From: Ben Hutchings Date: Tue, 14 Aug 2012 08:54:51 +0000 (+0000) Subject: ipv6: addrconf: Avoid calling netdevice notifiers with RCU read-side lock X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=4acd4945cd1e1f92b20d14e349c6c6a52acbd42d;p=openwrt%2Fstaging%2Fblogic.git ipv6: addrconf: Avoid calling netdevice notifiers with RCU read-side lock Cong Wang reports that lockdep detected suspicious RCU usage while enabling IPV6 forwarding: [ 1123.310275] =============================== [ 1123.442202] [ INFO: suspicious RCU usage. ] [ 1123.558207] 3.6.0-rc1+ #109 Not tainted [ 1123.665204] ------------------------------- [ 1123.768254] include/linux/rcupdate.h:430 Illegal context switch in RCU read-side critical section! [ 1123.992320] [ 1123.992320] other info that might help us debug this: [ 1123.992320] [ 1124.307382] [ 1124.307382] rcu_scheduler_active = 1, debug_locks = 0 [ 1124.522220] 2 locks held by sysctl/5710: [ 1124.648364] #0: (rtnl_mutex){+.+.+.}, at: [] rtnl_trylock+0x15/0x17 [ 1124.882211] #1: (rcu_read_lock){.+.+.+}, at: [] rcu_lock_acquire+0x0/0x29 [ 1125.085209] [ 1125.085209] stack backtrace: [ 1125.332213] Pid: 5710, comm: sysctl Not tainted 3.6.0-rc1+ #109 [ 1125.441291] Call Trace: [ 1125.545281] [] lockdep_rcu_suspicious+0x109/0x112 [ 1125.667212] [] rcu_preempt_sleep_check+0x45/0x47 [ 1125.781838] [] __might_sleep+0x1e/0x19b [...] [ 1127.445223] [] call_netdevice_notifiers+0x4a/0x4f [...] [ 1127.772188] [] dev_disable_lro+0x32/0x6b [ 1127.885174] [] dev_forward_change+0x30/0xcb [ 1128.013214] [] addrconf_forward_change+0x85/0xc5 [...] addrconf_forward_change() uses RCU iteration over the netdev list, which is unnecessary since it already holds the RTNL lock. We also cannot reasonably require netdevice notifier functions not to sleep. Reported-by: Cong Wang Signed-off-by: Ben Hutchings Signed-off-by: David S. Miller --- diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index 79181819a24f..6bc85f7c31e3 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -494,8 +494,7 @@ static void addrconf_forward_change(struct net *net, __s32 newf) struct net_device *dev; struct inet6_dev *idev; - rcu_read_lock(); - for_each_netdev_rcu(net, dev) { + for_each_netdev(net, dev) { idev = __in6_dev_get(dev); if (idev) { int changed = (!idev->cnf.forwarding) ^ (!newf); @@ -504,7 +503,6 @@ static void addrconf_forward_change(struct net *net, __s32 newf) dev_forward_change(idev); } } - rcu_read_unlock(); } static int addrconf_fixup_forwarding(struct ctl_table *table, int *p, int newf)