On Fri, Dec 11, 2015 at 03:43:13PM +0100, Florian Westphal wrote: > Florian Westphal <fw@xxxxxxxxx> wrote: > > Ulrich reports soft lockup with following (shortened) callchain: > > > > NMI watchdog: BUG: soft lockup - CPU#1 stuck for 22s! > > __netif_receive_skb_core+0x6e4/0x774 > > process_backlog+0x94/0x160 > > net_rx_action+0x88/0x178 > > call_do_softirq+0x24/0x3c > > do_softirq+0x54/0x6c > > __local_bh_enable_ip+0x7c/0xbc > > nf_ct_iterate_cleanup+0x11c/0x22c [nf_conntrack] > > masq_inet_event+0x20/0x30 [nf_nat_masquerade_ipv6] > > atomic_notifier_call_chain+0x1c/0x2c > > ipv6_del_addr+0x1bc/0x220 [ipv6] > > > > Problem is that nf_ct_iterate_cleanup can run for a very long time > > since it can be interrupted by softirq processing. > > Moreover, atomic_notifier_call_chain runs with rcu readlock held. > > Ulrich just reported another softlockup even with this patch applied. > > One explanation would be non-matching iter(), in this case > get_next_corpse can take forever since it will walk the entire conntrack > table, rendering the cond_resched moot. Probably another reincarnation of 0838aa7fcfcd? Is Ulrich using conntrack templates? > A V2 patch will be coming to also add a lock break + resched to > get_next_corpse. BTW, the atomic chain notifier in IPv6 seems to be there to handle this update from the packet path: ndisc_rcv() ndisc_router_discovery() addrconf_prefix_rcv() manage_tempaddrs() ipv6_add_addr() inet6addr_notifier_call_chain() Probably we can get Hannes have a look into this, I think we can convert this chain to blocking one through workqueue since addrconf_prefix_rcv() returns void. The remaining call sites of inet6addr_notifier_call_chain() that I could tracked come from paths where I can see ASSERT_RTNL(), so user context is guaranteed. I'm telling this become I remember that we discussed in netconf'14 Chicago that it would be good to get rid of this kind og asymmetries between IPv4 and IPv6. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
