nas: remove all uses of atomic from 4G and 5G classes

the NAS classes aren't thread safe and thread-safety shouldn't be
pretended by using atomics. Remove them and add explicit notice.

srsue/hdr/stack/upper/nas.h

@@ -35,6 +35,13 @@ class usim_interface_nas;
 class gw_interface_nas;
 class rrc_interface_nas;
 
+/**
+ * @brief This class implements the NAS layer of a EUTRA UE.
+ *
+ * The class is *NOT* thread-safe.
+ *
+ */
+
 class nas : public nas_interface_rrc, public srsran::timer_callback, public nas_base
 {
 public:

srsue/hdr/stack/upper/nas_5g.h

@@ -33,6 +33,12 @@ using srsran::byte_buffer_t;
 
 namespace srsue {
 
+/**
+ * @brief This class implements the NAS layer of a 5G UE.
+ *
+ * The class is *NOT* thread-safe.
+ *
+ */
 class nas_5g : public nas_base, public nas_5g_interface_rrc_nr, public nas_5g_interface_procedures
 {
 public:

srsue/hdr/stack/upper/nas_5gmm_state.h

@@ -74,9 +74,9 @@ public:
   const std::string get_full_state_text();
 
 private:
-  std::atomic<state_t>    state{state_t::null};
-  std::atomic<deregistered_substate_t> deregistered_substate{deregistered_substate_t::null};
-  std::atomic<registered_substate_t>   registered_substate{registered_substate_t::null};
+  state_t                 state                 = state_t::null;
+  deregistered_substate_t deregistered_substate = deregistered_substate_t::null;
+  registered_substate_t   registered_substate   = registered_substate_t::null;
   srslog::basic_logger&   logger                = srslog::fetch_basic_logger("NAS-5G");
 };
 

srsue/hdr/stack/upper/nas_emm_state.h

@@ -14,7 +14,6 @@
 #define SRSUE_NAS_EMM_STATE_H
 
 #include "srsran/srslog/srslog.h"
-#include <atomic>
 #include <string>
 
 namespace srsue {
@@ -77,9 +76,9 @@ public:
   const std::string get_full_state_text();
 
 private:
-  std::atomic<state_t> state{state_t::null}; // The GW might require to know the NAS state from another thread
-  std::atomic<deregistered_substate_t> deregistered_substate{deregistered_substate_t::null};
-  std::atomic<registered_substate_t>   registered_substate{registered_substate_t::null};
+  state_t                 state                 = state_t::null;
+  deregistered_substate_t deregistered_substate = deregistered_substate_t::null;
+  registered_substate_t   registered_substate   = registered_substate_t::null;
   srslog::basic_logger&   logger                = srslog::fetch_basic_logger("NAS");
 };