Restored exercise2 to original form

exercise2-1/src/inverted_pendulum/include/inverted_pendulum/message_passing/single_data.h

@@ -7,18 +7,20 @@
 struct SingleData {
   // Exercise2-1: Remove the lock from this function
   void Set(const double value) {
+    std::scoped_lock lock(mutex_);
     value_ = value;
   }
 
   // Exercise2-1: Remove the lock from this function
   double Get() {
+    std::scoped_lock lock(mutex_);
     return value_;
   }
 
  private:
   // Exercise2-1: Remove the lock and replace the double with a std::atomic<double>
-  static_assert(std::atomic<double>::is_always_lock_free);
-  std::atomic<double>     value_;
+  std::mutex mutex_;
+  double     value_;
 };
 
 #endif

exercise2-2/src/inverted_pendulum/include/inverted_pendulum/message_passing/multiple_data.h

@@ -25,7 +25,7 @@ struct MultipleData {
  private:
   // Exercise 2-2: Change this mutex to a priority inheritance mutex
   // A priority inheritance mutex implementation is available as cactus_rt::mutex
-  using mutex = cactus_rt::mutex;
+  using mutex = std::mutex;
   mutex pid_constant_mutex_;
 
   PIDConstants pid_constants_;