Ensure ROM class cache shutdown is necessary

Signed-off-by: Christian Despres <[email protected]>

runtime/compiler/runtime/JITClientSession.cpp

@@ -1226,6 +1226,8 @@ ClientSessionHT::purgeOldDataIfNeeded()
             oldAge = OLD_AGE_UNDER_LOW_MEMORY; //memory is low
             }
          }
+
+      bool hadExistingClients = !_clientSessionMap.empty();
       // Time for a purge operation.
       // Scan the entire table and delete old elements that are not in use
       for (auto iter = _clientSessionMap.begin(); iter != _clientSessionMap.end(); ++iter)
@@ -1241,8 +1243,8 @@ ClientSessionHT::purgeOldDataIfNeeded()
             _clientSessionMap.erase(iter); // delete the mapping from the hashtable
             }
          }
-      // If all the clients were deleted, shut down the shared ROMClass cache
-      if (_clientSessionMap.empty())
+      // If the purge operation was responsible for deleting the last client sessions, shut down the shared ROM class cache as well
+      if (hadExistingClients && _clientSessionMap.empty())
          {
          if (auto cache = TR::CompilationInfo::get()->getJITServerSharedROMClassCache())
             cache->shutdown();