[ovs-dev] [PATCH] route-table: Make route-table module thread-safe.

[Ryan Wilson]

Due to patch fe83f8 (netdev: Remove netdev from global shash when
the user is changing interface configuration), netdevs can be
destructed and deallocated by revalidator and RCU threads. When
netdevs with class vport are destroyed, the routing table is
unregistered, possibly causing memory to be freed. This causes a
race condition with the main thread which calls route_table_run
periodically to check for routing table updates.

This patch makes the route-table module thread-safe via a mutex.

Bug #1258532
Signed-off-by: Ryan Wilson <wryan at nicira.com>
---
 lib/route-table.c |   19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/lib/route-table.c b/lib/route-table.c
index 2986d3d..19bd414 100644
--- a/lib/route-table.c
+++ b/lib/route-table.c
@@ -63,6 +63,7 @@ struct name_node {
     char ifname[IFNAMSIZ]; /* Interface name. */
 };
 
+static struct ovs_mutex route_table_mutex = OVS_MUTEX_INITIALIZER;
 static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 20);
 
 /* Global change number for route-table, which should be incremented
@@ -102,9 +103,12 @@ static struct name_node *name_node_lookup(int ifi_index);
  * Returns true if successful, otherwise false. */
 bool
 route_table_get_name(ovs_be32 ip, char name[IFNAMSIZ])
+    OVS_EXCLUDED(route_table_mutex)
 {
     int ifindex;
 
+    ovs_mutex_lock(&route_table_mutex);
+
     if (!name_table_valid) {
         name_table_reset();
     }
@@ -115,10 +119,12 @@ route_table_get_name(ovs_be32 ip, char name[IFNAMSIZ])
         nn = name_node_lookup(ifindex);
         if (nn) {
             ovs_strlcpy(name, nn->ifname, IFNAMSIZ);
+            ovs_mutex_unlock(&route_table_mutex);
             return true;
         }
     }
 
+    ovs_mutex_unlock(&route_table_mutex);
     return false;
 }
 
@@ -130,6 +136,7 @@ route_table_get_name(ovs_be32 ip, char name[IFNAMSIZ])
  * Returns true if successful, otherwise false. */
 bool
 route_table_get_ifindex(ovs_be32 ip_, int *ifindex)
+    OVS_REQUIRES(route_table_mutex)
 {
     struct route_node *rn;
     uint32_t ip = ntohl(ip_);
@@ -168,7 +175,9 @@ route_table_get_change_seq(void)
  * function before making any other route_table function calls. */
 void
 route_table_register(void)
+    OVS_EXCLUDED(route_table_mutex)
 {
+    ovs_mutex_lock(&route_table_mutex);
     if (!register_count) {
         ovs_assert(!nln);
         ovs_assert(!route_notifier);
@@ -186,6 +195,7 @@ route_table_register(void)
     }
 
     register_count++;
+    ovs_mutex_unlock(&route_table_mutex);
 }
 
 /* Users of the route_table module should unregister themselves with this
@@ -193,7 +203,9 @@ route_table_register(void)
  * calls. */
 void
 route_table_unregister(void)
+    OVS_EXCLUDED(route_table_mutex)
 {
+    ovs_mutex_lock(&route_table_mutex);
     register_count--;
 
     if (!register_count) {
@@ -206,12 +218,15 @@ route_table_unregister(void)
         hmap_destroy(&route_map);
         name_table_uninit();
     }
+    ovs_mutex_unlock(&route_table_mutex);
 }
 
 /* Run periodically to update the locally maintained routing table. */
 void
 route_table_run(void)
+    OVS_EXCLUDED(route_table_mutex)
 {
+    ovs_mutex_lock(&route_table_mutex);
     if (nln) {
         rtnetlink_link_run();
         nln_run(nln);
@@ -220,16 +235,20 @@ route_table_run(void)
             route_table_reset();
         }
     }
+    ovs_mutex_unlock(&route_table_mutex);
 }
 
 /* Causes poll_block() to wake up when route_table updates are required. */
 void
 route_table_wait(void)
+    OVS_EXCLUDED(route_table_mutex)
 {
+    ovs_mutex_lock(&route_table_mutex);
     if (nln) {
         rtnetlink_link_wait();
         nln_wait(nln);
     }
+    ovs_mutex_unlock(&route_table_mutex);
 }
 
 static int
-- 
1.7.9.5