Add cling::internal::SpinLockGuard

lib/Interpreter/Threading.h

@@ -0,0 +1,46 @@
+//--------------------------------------------------------------------*- C++ -*-
+// CLING - the C++ LLVM-based InterpreterG :)
+// author:  Philippe Canal <pcanal@fnal.gov>
+//
+// This file is dual-licensed: you can choose to license it under the University
+// of Illinois Open Source License or the GNU Lesser General Public License. See
+// LICENSE.TXT for details.
+//------------------------------------------------------------------------------
+
+#ifndef CLING_THREADING_H
+#define CLING_THREADING_H
+
+
+#include <atomic>
+
+namespace cling {
+namespace internal {
+
+   class SpinLockGuard {
+      // Trivial spin lock guard
+
+   private:
+      ///\brief The atomic flag to be used as a spin lock.
+      ///
+      std::atomic_flag& m_Flag;
+
+   public:
+      ///\brief Spin until we until the flag becomes (or is) false
+      ///
+      SpinLockGuard(std::atomic_flag& aflag) : m_Flag(aflag)
+      {
+         while (m_Flag.test_and_set(std::memory_order_acquire));
+      }
+
+      //\brief Release the lock by setting the false to false.
+      ~SpinLockGuard()
+      {
+         m_Flag.clear(std::memory_order_release);
+      }
+
+   };
+
+} // end of internal namespace
+} // end of cling namespace
+
+#endif // end of CLING_THREADING_H