core: Make global io_service and scheduler thread-local

Change-Id: I3d6b6cd3ca7a6e53b0dc0f4cae7a2f3270c7fd50
Refs: #2489
diff --git a/core/global-io.cpp b/core/global-io.cpp
index f8d8270..48566f6 100644
--- a/core/global-io.cpp
+++ b/core/global-io.cpp
@@ -1,11 +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
+ * 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.
@@ -20,9 +21,10 @@
  *
  * You should have received a copy of the GNU General Public License along with
  * NFD, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
- **/
+ */
 
 #include "global-io.hpp"
+#include <boost/thread/tss.hpp>
 
 namespace nfd {
 
@@ -32,13 +34,14 @@
 resetGlobalScheduler();
 } // namespace scheduler
 
-static shared_ptr<boost::asio::io_service> g_ioService;
+
+static boost::thread_specific_ptr<boost::asio::io_service> g_ioService;
 
 boost::asio::io_service&
 getGlobalIoService()
 {
-  if (!static_cast<bool>(g_ioService)) {
-    g_ioService = make_shared<boost::asio::io_service>();
+  if (g_ioService.get() == nullptr) {
+    g_ioService.reset(new boost::asio::io_service());
   }
   return *g_ioService;
 }