3.0-stable review patch. If anyone has any objections, please let me know.
------------------
From: Ben Hutchings <bhutchi...@solarflare.com>
[ 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 <amw...@redhat.com>
Signed-off-by: Ben Hutchings <bhutchi...@solarflare.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
net/ipv6/addrconf.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -492,8 +492,7 @@ static void addrconf_forward_change(stru
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(stru
dev_forward_change(idev);
}
}
- rcu_read_unlock();
}
static int addrconf_fixup_forwarding(struct ctl_table *table, int *p, int old)
--
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