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



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 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;
 }


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