Acquire lock to check for genesis block.

src/init.cpp

@@ -1371,11 +1371,19 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
             vImportFiles.push_back(strFile);
     }
     threadGroup.create_thread(boost::bind(&ThreadImport, vImportFiles));
-    if (chainActive.Tip() == NULL) {
-        LogPrintf("Waiting for genesis block to be imported...\n");
-        while (!fRequestShutdown && chainActive.Tip() == NULL)
+
+    // Wait for genesis block to be processed
+    bool fHaveGenesis = false;
+    while (!fHaveGenesis && !fRequestShutdown) {
+        {
+            LOCK(cs_main);
+            fHaveGenesis = (chainActive.Tip() != NULL);
+        }
+
+        if (!fHaveGenesis) {
             MilliSleep(10);
         }
+    }
 
     // ********************************************************* Step 11: start node