IPVS netns shutdown/startup dead-lock

ip_vs_mutext is used by both netns shutdown code and startup
and both implicit uses sk_lock-AF_INET mutex.

cleanup CPU-1         startup CPU-2
ip_vs_dst_event()     ip_vs_genl_set_cmd()
 sk_lock-AF_INET     __ip_vs_mutex
                     sk_lock-AF_INET
__ip_vs_mutex
* DEAD LOCK *

A new mutex placed in ip_vs netns struct called sync_mutex is added.

Comments from Julian and Simon added.
This patch has been running for more than 3 month now and it seems to work.

Ver. 3
    IP_VS_SO_GET_DAEMON in do_ip_vs_get_ctl protected by sync_mutex
    instead of __ip_vs_mutex as sugested by Julian.

Signed-off-by: Hans Schillstrom <hans@schillstrom.com>
Acked-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h
index 1aaf915656f3..8fa4430f99c1 100644
--- a/include/net/ip_vs.h
+++ b/include/net/ip_vs.h
@@ -900,6 +900,7 @@ struct netns_ipvs {
         volatile int            sync_state;
         volatile int            master_syncid;
         volatile int            backup_syncid;
+        struct mutex            sync_mutex;
         /* multicast interface name */
         char                    master_mcast_ifn[IP_VS_IFNAME_MAXLEN];
         char                    backup_mcast_ifn[IP_VS_IFNAME_MAXLEN];