QPID-4672: C++ Broker deadlock in XmlExchange unbind

Unbind functions get the Wlock directly and do not get Rlock first.



git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk/qpid@1461634 13f79535-47bb-0310-9956-ffa450edef68

2 files changed, 12 insertions, 3 deletions

diff --git a/cpp/src/qpid/xml/XmlExchange.cpp b/cpp/src/qpid/xml/XmlExchange.cpp
index fb6c326327..29c00d9c12 100644
--- a/cpp/src/qpid/xml/XmlExchange.cpp
+++ b/cpp/src/qpid/xml/XmlExchange.cpp
@@ -179,17 +179,24 @@ bool XmlExchange::bind(Queue::shared_ptr queue, const std::string& bindingKey, c
 
 bool XmlExchange::unbind(Queue::shared_ptr queue, const std::string& bindingKey, const FieldTable* args)
 {
+    RWlock::ScopedWlock l(lock);
+    return unbindLH(queue, bindingKey, args);
+}
+
+bool XmlExchange::unbindLH(Queue::shared_ptr queue, const std::string& bindingKey, const FieldTable* args)
+{
     /*
      *  When called directly, no qpidFedOrigin argument will be
      *  present. When called from federation, it will be present. 
      *
      *  This is a bit of a hack - the binding needs the origin, but
      *  this interface, as originally defined, would not supply one.
+     *
+     *  Note: caller must hold Wlock
      */
     std::string fedOrigin;
     if (args) fedOrigin = args->getAsString(qpidFedOrigin);
 
-    RWlock::ScopedWlock l(lock);
     if (bindingsMap[bindingKey].remove_if(MatchQueueAndOrigin(queue, fedOrigin))) {
         if (mgmtExchange != 0) {
             mgmtExchange->dec_bindingCount();
@@ -389,9 +396,9 @@ void XmlExchange::propagateFedOp(const std::string& bindingKey, const std::strin
 
 bool XmlExchange::fedUnbind(const std::string& fedOrigin, const std::string& fedTags, Queue::shared_ptr queue, const std::string& bindingKey, const FieldTable* args)
 {
-    RWlock::ScopedRlock l(lock);
+    RWlock::ScopedWlock l(lock);
 
-    if (unbind(queue, bindingKey, args)) {
+    if (unbindLH(queue, bindingKey, args)) {
         propagateFedOp(bindingKey, fedTags, fedOpUnbind, fedOrigin); 
         return true;
     }
diff --git a/cpp/src/qpid/xml/XmlExchange.h b/cpp/src/qpid/xml/XmlExchange.h
index 7b04781ad5..fd3f8d0278 100644
--- a/cpp/src/qpid/xml/XmlExchange.h
+++ b/cpp/src/qpid/xml/XmlExchange.h
@@ -107,6 +107,8 @@ class XmlExchange : public virtual Exchange {
         bool operator()(XmlBinding::shared_ptr b);
     };
 
+  private:
+    bool unbindLH(Queue::shared_ptr queue, const std::string& routingKey, const qpid::framing::FieldTable* args);
 };