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authorBen Hutchings <bhutchings@solarflare.com>2012-08-14 08:54:51 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-10-02 09:47:05 -0700
commitf9b6caca04a5444f61c1b08ebf04c6f2c6ff2ec9 (patch)
treea556442a8e3a6cea7de9dd1b12f3f5a9c2eb7ca8 /net
parent2d1244f43868053b12684af2f9fe918c5641d898 (diff)
ipv6: addrconf: Avoid calling netdevice notifiers with RCU read-side lock
[ Upstream commit 4acd4945cd1e1f92b20d14e349c6c6a52acbd42d ] 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: [<ffffffff81768498>] rtnl_trylock+0x15/0x17 [ 1124.882211] #1: (rcu_read_lock){.+.+.+}, at: [<ffffffff81871df8>] 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] [<ffffffff8109d915>] lockdep_rcu_suspicious+0x109/0x112 [ 1125.667212] [<ffffffff8107c240>] rcu_preempt_sleep_check+0x45/0x47 [ 1125.781838] [<ffffffff8107c260>] __might_sleep+0x1e/0x19b [...] [ 1127.445223] [<ffffffff81757ac5>] call_netdevice_notifiers+0x4a/0x4f [...] [ 1127.772188] [<ffffffff8175e125>] dev_disable_lro+0x32/0x6b [ 1127.885174] [<ffffffff81872d26>] dev_forward_change+0x30/0xcb [ 1128.013214] [<ffffffff818738c4>] 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 <amwang@redhat.com> Signed-off-by: Ben Hutchings <bhutchings@solarflare.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net')
-rw-r--r--net/ipv6/addrconf.c4
1 files changed, 1 insertions, 3 deletions
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index be29337ea39..70d6a7fff10 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -492,8 +492,7 @@ 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);
@@ -502,7 +501,6 @@ 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 old)