4.2.8-ckt5 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: "subashab@xxxxxxxxxxxxxx" <subashab@xxxxxxxxxxxxxx> [ Upstream commit 16186a82de1fdd868255448274e64ae2616e2640 ] A rcu stall with the following backtrace was seen on a system with forwarding, optimistic_dad and use_optimistic set. To reproduce, set these flags and allow ipv6 autoconf. This occurs because the device write_lock is acquired while already holding the read_lock. Back trace below - INFO: rcu_preempt self-detected stall on CPU { 1} (t=2100 jiffies g=3992 c=3991 q=4471) <6> Task dump for CPU 1: <2> kworker/1:0 R running task 12168 15 2 0x00000002 <2> Workqueue: ipv6_addrconf addrconf_dad_work <6> Call trace: <2> [<ffffffc000084da8>] el1_irq+0x68/0xdc <2> [<ffffffc000cc4e0c>] _raw_write_lock_bh+0x20/0x30 <2> [<ffffffc000bc5dd8>] __ipv6_dev_ac_inc+0x64/0x1b4 <2> [<ffffffc000bcbd2c>] addrconf_join_anycast+0x9c/0xc4 <2> [<ffffffc000bcf9f0>] __ipv6_ifa_notify+0x160/0x29c <2> [<ffffffc000bcfb7c>] ipv6_ifa_notify+0x50/0x70 <2> [<ffffffc000bd035c>] addrconf_dad_work+0x314/0x334 <2> [<ffffffc0000b64c8>] process_one_work+0x244/0x3fc <2> [<ffffffc0000b7324>] worker_thread+0x2f8/0x418 <2> [<ffffffc0000bb40c>] kthread+0xe0/0xec v2: do addrconf_dad_kick inside read lock and then acquire write lock for ipv6_ifa_notify as suggested by Eric Fixes: 7fd2561e4ebdd ("net: ipv6: Add a sysctl to make optimistic addresses useful candidates") Cc: Eric Dumazet <edumazet@xxxxxxxxxx> Cc: Erik Kline <ek@xxxxxxxxxx> Cc: Hannes Frederic Sowa <hannes@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@xxxxxxxxxxxxxx> Acked-by: Hannes Frederic Sowa <hannes@xxxxxxxxxxxxxxxxxxx> Acked-by: Eric Dumazet <edumazet@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx> --- net/ipv6/addrconf.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index 54fb696..ff6e0dc 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -3425,6 +3425,7 @@ static void addrconf_dad_begin(struct inet6_ifaddr *ifp) { struct inet6_dev *idev = ifp->idev; struct net_device *dev = idev->dev; + bool notify = false; addrconf_join_solict(dev, &ifp->addr); @@ -3470,7 +3471,7 @@ static void addrconf_dad_begin(struct inet6_ifaddr *ifp) /* Because optimistic nodes can use this address, * notify listeners. If DAD fails, RTM_DELADDR is sent. */ - ipv6_ifa_notify(RTM_NEWADDR, ifp); + notify = true; } } @@ -3478,6 +3479,8 @@ static void addrconf_dad_begin(struct inet6_ifaddr *ifp) out: spin_unlock(&ifp->lock); read_unlock_bh(&idev->lock); + if (notify) + ipv6_ifa_notify(RTM_NEWADDR, ifp); } static void addrconf_dad_start(struct inet6_ifaddr *ifp) -- 2.7.0 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html