[libvirt] [PATCH] nwfilter: re-order lock grabbed by IP addr. learn thread

[Stefan Berger]

The IP address learning thread was causing a deadlock when it 
instantiated a filter while a filter update/change was ongoing. The 
reason for this was the ordering of locks due to the following calls

virNWFilterUnlockFilterUpdates()
virNWFilterPoolObjFindByName()

The below patch now puts the order of the locks in the above shown order 
when instantiating the filter from the IP address learning thread.

Signed-off-by: Stefan Berger <stefanb at us.ibm.com>

---
  src/nwfilter/nwfilter_gentech_driver.c |   45 
++++++++++++++++++++-------------
  1 file changed, 28 insertions(+), 17 deletions(-)

Index: libvirt-acl/src/nwfilter/nwfilter_gentech_driver.c
===================================================================
--- libvirt-acl.orig/src/nwfilter/nwfilter_gentech_driver.c
+++ libvirt-acl/src/nwfilter/nwfilter_gentech_driver.c
@@ -552,6 +552,8 @@ virNWFilterRuleInstancesToArray(int nEnt
   * all its subfilters in a depth-first traversal of the tree of referenced
   * filters. The name of the interface to which the rules belong must be
   * provided. Apply the values of variables as needed.
+ *
+ * Call this function while holding the NWFilter filter update lock
   */
  static int
  virNWFilterInstantiate(virConnectPtr conn,
@@ -575,8 +577,6 @@ virNWFilterInstantiate(virConnectPtr con
      void **ptrs = NULL;
      int instantiate = 1;

-    virNWFilterLockFilterUpdates();
-
      virNWFilterHashTablePtr missing_vars = virNWFilterHashTableCreate(0);
      if (!missing_vars) {
          virReportOOMError();
@@ -668,8 +668,6 @@ virNWFilterInstantiate(virConnectPtr con

  err_exit:

-    virNWFilterUnlockFilterUpdates();
-
      for (j = 0; j < nEntries; j++)
          virNWFilterRuleInstFree(insts[j]);

@@ -681,6 +679,7 @@ err_exit:
  }


+ * Call this function while holding the NWFilter filter update lock
  static int
  __virNWFilterInstantiateFilter(virConnectPtr conn,
                                 bool teardownOld,
@@ -823,23 +822,30 @@ _virNWFilterInstantiateFilter(virConnect
                            ? net->data.direct.linkdev
                            : NULL;
      int ifindex;
+    int rc;

      if (ifaceGetIndex(true, net->ifname, &ifindex))
          return 1;

-    return __virNWFilterInstantiateFilter(conn,
-                                          teardownOld,
-                                          net->ifname,
-                                          ifindex,
-                                          linkdev,
-                                          net->type,
-                                          net->mac,
-                                          net->filter,
-                                          net->filterparams,
-                                          useNewFilter,
-                                          conn->nwfilterPrivateData,
-                                          false,
-                                          foundNewFilter);
+    virNWFilterLockFilterUpdates();
+
+    rc = __virNWFilterInstantiateFilter(conn,
+                                        teardownOld,
+                                        net->ifname,
+                                        ifindex,
+                                        linkdev,
+                                        net->type,
+                                        net->mac,
+                                        net->filter,
+                                        net->filterparams,
+                                        useNewFilter,
+                                        conn->nwfilterPrivateData,
+                                        false,
+                                        foundNewFilter);
+
+    virNWFilterUnlockFilterUpdates();
+
+    return rc;
  }


@@ -857,6 +863,8 @@ virNWFilterInstantiateFilterLate(virConn
      int rc;
      bool foundNewFilter = false;

+    virNWFilterLockFilterUpdates();
+
      rc = __virNWFilterInstantiateFilter(conn,
                                          1,
                                          ifname,
@@ -878,6 +886,9 @@ virNWFilterInstantiateFilterLate(virConn
              _virNWFilterTeardownFilter(ifname);
          }
      }
+
+    virNWFilterUnlockFilterUpdates();
+
      return rc;
  }