re PR libstdc++/59215 (tsan: warning in shared_ptr_base.h)

	PR libstdc++/59215
	* include/bits/shared_ptr_base.h
	(_Sp_counted_base<_S_atomic>::_M_add_ref_lock()): Use relaxed atomic
	load.

From-SVN: r207147

libstdc++-v3/ChangeLog

+2014-01-27  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR libstdc++/59215
+	* include/bits/shared_ptr_base.h
+	(_Sp_counted_base<_S_atomic>::_M_add_ref_lock()): Use relaxed atomic
+	load.
+
 2014-01-27  Jason Merrill  <jason@redhat.com>
 
 	Core DR 475

libstdc++-v3/include/bits/shared_ptr_base.h

@@ -233,7 +233,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     _M_add_ref_lock()
     {
       // Perform lock-free add-if-not-zero operation.
-      _Atomic_word __count = _M_use_count;
+      _Atomic_word __count = _M_get_use_count();
       do
 	{
 	  if (__count == 0)