core: Make global io_service and scheduler thread-local

Change-Id: I3d6b6cd3ca7a6e53b0dc0f4cae7a2f3270c7fd50
Refs: #2489
diff --git a/core/scheduler.cpp b/core/scheduler.cpp
index 0979f97..177045f 100644
--- a/core/scheduler.cpp
+++ b/core/scheduler.cpp
@@ -1,12 +1,12 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2014,  Regents of the University of California,
- *                      Arizona Board of Regents,
- *                      Colorado State University,
- *                      University Pierre & Marie Curie, Sorbonne University,
- *                      Washington University in St. Louis,
- *                      Beijing Institute of Technology,
- *                      The University of Memphis
+ * Copyright (c) 2014-2015,  Regents of the University of California,
+ *                           Arizona Board of Regents,
+ *                           Colorado State University,
+ *                           University Pierre & Marie Curie, Sorbonne University,
+ *                           Washington University in St. Louis,
+ *                           Beijing Institute of Technology,
+ *                           The University of Memphis.
  *
  * This file is part of NFD (Named Data Networking Forwarding Daemon).
  * See AUTHORS.md for complete list of NFD authors and contributors.
@@ -26,17 +26,20 @@
 #include "scheduler.hpp"
 #include "global-io.hpp"
 
+#include <boost/thread/tss.hpp>
+
 namespace nfd {
 namespace scheduler {
 
-static shared_ptr<Scheduler> g_scheduler;
+static boost::thread_specific_ptr<Scheduler> g_scheduler;
 
-inline Scheduler&
+Scheduler&
 getGlobalScheduler()
 {
-  if (!static_cast<bool>(g_scheduler)) {
-    g_scheduler = make_shared<Scheduler>(ref(getGlobalIoService()));
+  if (g_scheduler.get() == nullptr) {
+    g_scheduler.reset(new Scheduler(getGlobalIoService()));
   }
+
   return *g_scheduler;
 }