Break deadlock caused when ClusterTimer::drop is called concurrently with Timer::add.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk/qpid@995426 13f79535-47bb-0310-9956-ffa450edef68

2 files changed, 8 insertions, 6 deletions

diff --git a/cpp/src/qpid/cluster/Cluster.cpp b/cpp/src/qpid/cluster/Cluster.cpp
index df0e612af7..5da1579cb7 100644
--- a/cpp/src/qpid/cluster/Cluster.cpp
+++ b/cpp/src/qpid/cluster/Cluster.cpp
@@ -1126,7 +1126,6 @@ void Cluster::timerDrop(const MemberId& , const std::string& name, Lock&) {
 }
 
 bool Cluster::isElder() const {
-    Monitor::ScopedLock l(lock);
     return elder;
 }
 
diff --git a/cpp/src/qpid/sys/Timer.cpp b/cpp/src/qpid/sys/Timer.cpp
index 3b627687de..76e8b3dc0b 100644
--- a/cpp/src/qpid/sys/Timer.cpp
+++ b/cpp/src/qpid/sys/Timer.cpp
@@ -107,16 +107,19 @@ void Timer::run()
             {
             ScopedLock<Mutex> l(t->callbackLock);
             if (t->cancelled) {
-                drop(t);
+                {
+                    Monitor::ScopedUnlock u(monitor);
+                    drop(t);
+                }
                 if (delay > lateCancel) {
-                    QPID_LOG(debug, t->name << " cancelled timer woken up " << delay / TIME_MSEC
-                             << "ms late");
+                    QPID_LOG(debug, t->name << " cancelled timer woken up " <<
+                             delay / TIME_MSEC << "ms late");
                 }
                 continue;
             } else if(Duration(t->nextFireTime, start) >= 0) {
                 {
-                Monitor::ScopedUnlock u(monitor);
-                fire(t);
+                    Monitor::ScopedUnlock u(monitor);
+                    fire(t);
                 }
                 // Warn if callback overran next timer's start.
                 AbsTime end(AbsTime::now());