Allow rlbox plugins to support threading

Author: shravanrn

code/include/rlbox_sandbox.hpp

@@ -79,11 +79,6 @@ struct rlbox_transition_timing
 };
 #endif
 
-#ifndef RLBOX_SINGLE_THREADED_INVOCATIONS
-#  error                                                                       \
-    "RLBox does not yet support threading. Please define RLBOX_SINGLE_THREADED_INVOCATIONS prior to including RLBox and ensure you are only using it from a single thread. If threading is required, please file a bug."
-#endif
-
 /**
  * @brief Encapsulation for sandboxes.
  *
@@ -97,6 +92,9 @@ class rlbox_sandbox : protected T_Sbx
 
 private:
 #ifdef RLBOX_MEASURE_TRANSITION_TIMES
+#ifndef RLBOX_SINGLE_THREADED_INVOCATIONS
+  RLBOX_SHARED_LOCK(transition_times_lock);
+#endif
   std::vector<rlbox_transition_timing> transition_times;
 #endif
 
@@ -109,6 +107,7 @@ class rlbox_sandbox : protected T_Sbx
   RLBOX_SHARED_LOCK(func_ptr_cache_lock);
   std::map<std::string, void*> func_ptr_map;
 
+  // This is thread-safe so no locks needed
   app_pointer_map<typename T_Sbx::T_PointerType> app_ptr_map;
 
   // This variable tracks of the sandbox has already been created/destroyed.
@@ -249,11 +248,16 @@ class rlbox_sandbox : protected T_Sbx
     auto on_exit = rlbox::detail::make_scope_exit([&] {
       auto exit_time = high_resolution_clock::now();
       int64_t ns = duration_cast<nanoseconds>(exit_time - enter_time).count();
-      sandbox.transition_times.push_back(
-        rlbox_transition_timing{ rlbox_transition::CALLBACK,
-                                 nullptr /* func_name */,
-                                 key /* func_ptr */,
-                                 ns });
+      {
+#ifndef RLBOX_SINGLE_THREADED_INVOCATIONS
+        RLBOX_ACQUIRE_UNIQUE_GUARD(transition_times_lock);
+#endif
+        sandbox.transition_times.push_back(
+          rlbox_transition_timing{ rlbox_transition::CALLBACK,
+                                  nullptr /* func_name */,
+                                  key /* func_ptr */,
+                                  ns });
+      }
     });
 #endif
 #ifdef RLBOX_TRANSITION_ACTION_OUT
@@ -752,8 +756,13 @@ class rlbox_sandbox : protected T_Sbx
     auto on_exit = rlbox::detail::make_scope_exit([&] {
       auto exit_time = high_resolution_clock::now();
       int64_t ns = duration_cast<nanoseconds>(exit_time - enter_time).count();
-      transition_times.push_back(rlbox_transition_timing{
-        rlbox_transition::INVOKE, func_name, func_ptr, ns });
+      {
+#ifndef RLBOX_SINGLE_THREADED_INVOCATIONS
+        RLBOX_ACQUIRE_UNIQUE_GUARD(transition_times_lock);
+#endif
+        transition_times.push_back(rlbox_transition_timing{
+          rlbox_transition::INVOKE, func_name, func_ptr, ns });
+      }
     });
 #endif
 #ifdef RLBOX_TRANSITION_ACTION_IN
@@ -1024,6 +1033,9 @@ class rlbox_sandbox : protected T_Sbx
   }
   inline int64_t get_total_ns_time_in_sandbox_and_transitions()
   {
+#ifndef RLBOX_SINGLE_THREADED_INVOCATIONS
+    RLBOX_ACQUIRE_SHARED_GUARD(transition_times_lock);
+#endif
     int64_t ret = 0;
     for (auto& transition_time : transition_times) {
       if (transition_time.invoke == rlbox_transition::INVOKE) {
@@ -1034,7 +1046,12 @@ class rlbox_sandbox : protected T_Sbx
     }
     return ret;
   }
-  inline void clear_transition_times() { transition_times.clear(); }
+  inline void clear_transition_times() {
+#ifndef RLBOX_SINGLE_THREADED_INVOCATIONS
+    RLBOX_ACQUIRE_UNIQUE_GUARD(transition_times_lock);
+#endif
+    transition_times.clear();
+  }
 #endif
 };