5 files changed, 94 insertions, 91 deletions

diff --git a/src/lanes.cpp b/src/lanes.cpp
index 47ca79a..5fb81a3 100644
--- a/src/lanes.cpp
+++ b/src/lanes.cpp
@@ -434,7 +434,7 @@ static bool selfdestruct_remove(Lane* lane_)
                 *ref = lane_->selfdestruct_next;
                 lane_->selfdestruct_next = nullptr;
                 // the terminal shutdown should wait until the lane is done with its lua_close()
-                ++lane_->U->selfdestructing_count;
+                lane_->U->selfdestructing_count.fetch_add(1, std::memory_order_release);
                 found = true;
                 break;
             }
@@ -526,7 +526,7 @@ static int universe_gc( lua_State* L)
 
         // If some lanes are currently cleaning after themselves, wait until they are done.
         // They are no longer listed in the selfdestruct chain, but they still have to lua_close().
-        while (U->selfdestructing_count > 0)
+        while (U->selfdestructing_count.load(std::memory_order_acquire) > 0)
         {
             YIELD();
         }
@@ -569,7 +569,7 @@ static int universe_gc( lua_State* L)
 
     // If some lanes are currently cleaning after themselves, wait until they are done.
     // They are no longer listed in the selfdestruct chain, but they still have to lua_close().
-    while( U->selfdestructing_count > 0)
+    while (U->selfdestructing_count.load(std::memory_order_acquire) > 0)
     {
         YIELD();
     }
@@ -956,7 +956,7 @@ static THREAD_RETURN_T THREAD_CALLCONV lane_main(void* vs)
 
             lane->U->selfdestruct_cs.lock();
             // done with lua_close(), terminal shutdown sequence may proceed
-            --lane->U->selfdestructing_count;
+            lane->U->selfdestructing_count.fetch_sub(1, std::memory_order_release);
             lane->U->selfdestruct_cs.unlock();
 
             delete lane;
@@ -1000,13 +1000,13 @@ LUAG_FUNC(require)
     DEBUGSPEW_CODE(Universe* U = universe_get(L));
     STACK_CHECK_START_REL(L, 0);
     DEBUGSPEW_CODE(fprintf(stderr, INDENT_BEGIN "lanes.require %s BEGIN\n" INDENT_END, name));
-    DEBUGSPEW_CODE(++U->debugspew_indent_depth);
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_add(1, std::memory_order_relaxed));
     lua_pushvalue(L, lua_upvalueindex(1)); // "name" require
     lua_insert(L, 1); // require "name"
     lua_call(L, nargs, 1); // module
     populate_func_lookup_table(L, -1, name);
     DEBUGSPEW_CODE(fprintf(stderr, INDENT_BEGIN "lanes.require %s END\n" INDENT_END, name));
-    DEBUGSPEW_CODE(--U->debugspew_indent_depth);
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_sub(1, std::memory_order_relaxed));
     STACK_CHECK(L, 0);
     return 1;
 }
@@ -1026,10 +1026,10 @@ LUAG_FUNC(register)
     DEBUGSPEW_CODE(Universe* U = universe_get(L));
     STACK_CHECK_START_REL(L, 0); // "name" mod_table
     DEBUGSPEW_CODE(fprintf(stderr, INDENT_BEGIN "lanes.register %s BEGIN\n" INDENT_END, name));
-    DEBUGSPEW_CODE(++U->debugspew_indent_depth);
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_add(1, std::memory_order_relaxed));
     populate_func_lookup_table(L, -1, name);
     DEBUGSPEW_CODE(fprintf(stderr, INDENT_BEGIN "lanes.register %s END\n" INDENT_END, name));
-    DEBUGSPEW_CODE(--U->debugspew_indent_depth);
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_sub(1, std::memory_order_relaxed));
     STACK_CHECK(L, 0);
     return 0;
 }
@@ -1076,7 +1076,7 @@ LUAG_FUNC(lane_new)
 
     /* --- Create and prepare the sub state --- */
     DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "lane_new: setup\n" INDENT_END));
-    DEBUGSPEW_CODE( ++ U->debugspew_indent_depth);
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_add(1, std::memory_order_relaxed));
 
     // populate with selected libraries at the same time
     lua_State* const L2{ luaG_newstate(U, L, libs_str) };                   // L                                                                    // L2
@@ -1162,6 +1162,7 @@ LUAG_FUNC(lane_new)
         void success()
         {
             prepareUserData();
+            m_lane->m_ready.count_down();
             m_lane = nullptr;
         }
     } onExit{ L, lane, gc_cb_idx };
@@ -1193,7 +1194,7 @@ LUAG_FUNC(lane_new)
     {
         int nbRequired = 1;
         DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "lane_new: require 'required' list\n" INDENT_END));
-        DEBUGSPEW_CODE( ++ U->debugspew_indent_depth);
+        DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_add(1, std::memory_order_relaxed));
         // should not happen, was checked in lanes.lua before calling lane_new()
         if (lua_type(L, required_idx) != LUA_TTABLE)
         {
@@ -1238,7 +1239,7 @@ LUAG_FUNC(lane_new)
             lua_pop(L, 1);                                                  // func libs priority globals package required gc_cb [... args ...] n
             ++ nbRequired;
         }                                                                   // func libs priority globals package required gc_cb [... args ...]
-        DEBUGSPEW_CODE( -- U->debugspew_indent_depth);
+        DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_sub(1, std::memory_order_relaxed));
     }
     STACK_CHECK(L, 0);
     STACK_CHECK(L2, 0);                                                                                                                             //
@@ -1254,7 +1255,7 @@ LUAG_FUNC(lane_new)
             return luaL_error(L, "Expected table, got %s", luaL_typename(L, globals_idx));
         }
 
-        DEBUGSPEW_CODE( ++ U->debugspew_indent_depth);
+        DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_add(1, std::memory_order_relaxed));
         lua_pushnil(L);                                                     // func libs priority globals package required gc_cb [... args ...] nil
         // Lua 5.2 wants us to push the globals table on the stack
         lua_pushglobaltable(L2);                                                                                                                    // _G
@@ -1267,7 +1268,7 @@ LUAG_FUNC(lane_new)
         }                                                                   // func libs priority globals package required gc_cb [... args ...]
         lua_pop( L2, 1);                                                                                                                            //
 
-        DEBUGSPEW_CODE( -- U->debugspew_indent_depth);
+        DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_sub(1, std::memory_order_relaxed));
     }
     STACK_CHECK(L, 0);
     STACK_CHECK(L2, 0);
@@ -1275,11 +1276,11 @@ LUAG_FUNC(lane_new)
     // Lane main function
     if (lua_type(L, 1) == LUA_TFUNCTION)
     {
-        DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "lane_new: transfer lane body\n" INDENT_END));
-        DEBUGSPEW_CODE( ++ U->debugspew_indent_depth);
+        DEBUGSPEW_CODE(fprintf( stderr, INDENT_BEGIN "lane_new: transfer lane body\n" INDENT_END));
+        DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_add(1, std::memory_order_relaxed));
         lua_pushvalue(L, 1);                                                // func libs priority globals package required gc_cb [... args ...] func
         int const res{ luaG_inter_move(U, L, L2, 1, LookupMode::LaneBody) };// func libs priority globals package required gc_cb [... args ...]     // func
-        DEBUGSPEW_CODE( -- U->debugspew_indent_depth);
+        DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_sub(1, std::memory_order_relaxed));
         if (res != 0)
         {
             return luaL_error(L, "tried to copy unsupported types");
@@ -1302,10 +1303,10 @@ LUAG_FUNC(lane_new)
     if (nargs > 0)
     {
         int res;
-        DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "lane_new: transfer lane arguments\n" INDENT_END));
-        DEBUGSPEW_CODE( ++ U->debugspew_indent_depth);
+        DEBUGSPEW_CODE(fprintf( stderr, INDENT_BEGIN "lane_new: transfer lane arguments\n" INDENT_END));
+        DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_add(1, std::memory_order_relaxed));
         res = luaG_inter_move(U, L, L2, nargs, LookupMode::LaneBody);       // func libs priority globals package required gc_cb                    // func [... args ...]
-        DEBUGSPEW_CODE( -- U->debugspew_indent_depth);
+        DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_sub(1, std::memory_order_relaxed));
         if (res != 0)
         {
             return luaL_error(L, "tried to copy unsupported types");
@@ -1323,8 +1324,7 @@ LUAG_FUNC(lane_new)
     onExit.success();
     // we should have the lane userdata on top of the stack
     STACK_CHECK(L, 1);
-    lane->m_ready.count_down();
-    DEBUGSPEW_CODE(--U->debugspew_indent_depth);
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_sub(1, std::memory_order_relaxed));
     return 1;
 }
 
@@ -1922,13 +1922,13 @@ LUAG_FUNC(configure)
     STACK_GROW(L, 4);
     STACK_CHECK_START_ABS(L, 1);                                                          // settings
 
-    DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "%p: lanes.configure() BEGIN\n" INDENT_END, L));
-    DEBUGSPEW_CODE( if (U) ++ U->debugspew_indent_depth);
+    DEBUGSPEW_CODE(fprintf( stderr, INDENT_BEGIN "%p: lanes.configure() BEGIN\n" INDENT_END, L));
+    DEBUGSPEW_CODE(if (U) U->debugspew_indent_depth.fetch_add(1, std::memory_order_relaxed));
 
     if(U == nullptr)
     {
         U = universe_create( L);                                                          // settings universe
-        DEBUGSPEW_CODE( ++ U->debugspew_indent_depth);
+        DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_add(1, std::memory_order_relaxed));
         lua_newtable( L);                                                                 // settings universe mt
         lua_getfield(L, 1, "shutdown_timeout");                                           // settings universe mt shutdown_timeout
         lua_pushcclosure(L, universe_gc, 1);                                              // settings universe mt universe_gc
@@ -2070,7 +2070,7 @@ LUAG_FUNC(configure)
     CONFIG_REGKEY.setValue(L, [](lua_State* L) { lua_pushvalue(L, -2); });
     STACK_CHECK(L, 1);
     DEBUGSPEW_CODE(fprintf(stderr, INDENT_BEGIN "%p: lanes.configure() END\n" INDENT_END, L));
-    DEBUGSPEW_CODE(--U->debugspew_indent_depth);
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_sub(1, std::memory_order_relaxed));
     // Return the settings table
     return 1;
 }
diff --git a/src/macros_and_utils.h b/src/macros_and_utils.h
index 31027d6..e29e7fb 100644
--- a/src/macros_and_utils.h
+++ b/src/macros_and_utils.h
@@ -18,7 +18,7 @@ extern "C" {
 #if USE_DEBUG_SPEW()
 extern char const* debugspew_indent;
 #define INDENT_BEGIN "%.*s "
-#define INDENT_END , (U ? U->debugspew_indent_depth : 0), debugspew_indent
+#define INDENT_END , (U ? U->debugspew_indent_depth.load(std::memory_order_relaxed) : 0), debugspew_indent
 #define DEBUGSPEW_CODE(_code) _code
 #define DEBUGSPEW_PARAM_COMMA( param_) param_,
 #define DEBUGSPEW_COMMA_PARAM( param_) , param_
diff --git a/src/state.cpp b/src/state.cpp
index 55540c8..512009a 100644
--- a/src/state.cpp
+++ b/src/state.cpp
@@ -200,8 +200,8 @@ static void copy_one_time_settings( Universe* U, lua_State* L, lua_State* L2)
     STACK_CHECK_START_REL(L, 0);
     STACK_CHECK_START_REL(L2, 0);
 
-    DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "copy_one_time_settings()\n" INDENT_END));
-    DEBUGSPEW_CODE( ++ U->debugspew_indent_depth);
+    DEBUGSPEW_CODE(fprintf( stderr, INDENT_BEGIN "copy_one_time_settings()\n" INDENT_END));
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_add(1, std::memory_order_relaxed));
 
     CONFIG_REGKEY.pushValue(L);                                                    // config
     // copy settings from from source to destination registry
@@ -213,7 +213,7 @@ static void copy_one_time_settings( Universe* U, lua_State* L, lua_State* L2)
     CONFIG_REGKEY.setValue(L2, [](lua_State* L) { lua_insert(L, -2); });                                        // config
     STACK_CHECK( L2, 0);
     STACK_CHECK( L, 0);
-    DEBUGSPEW_CODE( -- U->debugspew_indent_depth);
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_sub(1, std::memory_order_relaxed));
 }
 
 void initialize_on_state_create( Universe* U, lua_State* L)
@@ -349,8 +349,8 @@ lua_State* luaG_newstate( Universe* U, lua_State* from_, char const* libs_)
         return L;
     }
 
-    DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "luaG_newstate()\n" INDENT_END));
-    DEBUGSPEW_CODE( ++ U->debugspew_indent_depth);
+    DEBUGSPEW_CODE(fprintf( stderr, INDENT_BEGIN "luaG_newstate()\n" INDENT_END));
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_add(1, std::memory_order_relaxed));
 
     // copy settings (for example because it may contain a Lua on_state_create function)
     copy_one_time_settings( U, from_, L);
@@ -423,22 +423,22 @@ lua_State* luaG_newstate( Universe* U, lua_State* from_, char const* libs_)
 
 #if 0 && USE_DEBUG_SPEW()
     // dump the lookup database contents
-    lua_getfield( L, LUA_REGISTRYINDEX, LOOKUP_REGKEY);                       // {}
-    lua_pushnil( L);                                                          // {} nil
-    while( lua_next( L, -2))                                                  // {} k v
+    lua_getfield(L, LUA_REGISTRYINDEX, LOOKUP_REGKEY);                                                    // {}
+    lua_pushnil(L);                                                                                       // {} nil
+    while (lua_next(L, -2))                                                                               // {} k v
     {
-        lua_getglobal( L, "print");                                             // {} k v print
-        lua_pushlstring( L, debugspew_indent, U->debugspew_indent_depth);       // {} k v print " "
-        lua_pushvalue( L, -4);                                                  // {} k v print " " k
-        lua_pushvalue( L, -4);                                                  // {} k v print " " k v
-        lua_call( L, 3, 0);                                                     // {} k v
-        lua_pop( L, 1);                                                         // {} k
+        lua_getglobal(L, "print");                                                                        // {} k v print
+        lua_pushlstring(L, debugspew_indent, U->debugspew_indent_depth.load(std::memory_order_relaxed));  // {} k v print " "
+        lua_pushvalue(L, -4);                                                                             // {} k v print " " k
+        lua_pushvalue(L, -4);                                                                             // {} k v print " " k v
+        lua_call(L, 3, 0);                                                                                // {} k v
+        lua_pop(L, 1);                                                                                    // {} k
     }
-    lua_pop( L, 1);                                                           // {}
+    lua_pop(L, 1);                                                                                        // {}
 #endif // USE_DEBUG_SPEW()
 
-    lua_pop( L, 1);
+    lua_pop(L, 1);
     STACK_CHECK(L, 0);
-    DEBUGSPEW_CODE(--U->debugspew_indent_depth);
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_sub(1, std::memory_order_relaxed));
     return L;
 }
diff --git a/src/tools.cpp b/src/tools.cpp
index df7602e..ac5f7c5 100644
--- a/src/tools.cpp
+++ b/src/tools.cpp
@@ -359,9 +359,9 @@ static void update_lookup_entry( DEBUGSPEW_PARAM_COMMA( Universe* U) lua_State*
 
     size_t prevNameLength, newNameLength;
     char const* prevName;
-    DEBUGSPEW_CODE( char const *newName);
-    DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "update_lookup_entry()\n" INDENT_END));
-    DEBUGSPEW_CODE( ++ U->debugspew_indent_depth);
+    DEBUGSPEW_CODE(char const *newName);
+    DEBUGSPEW_CODE(fprintf( stderr, INDENT_BEGIN "update_lookup_entry()\n" INDENT_END));
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_add(1, std::memory_order_relaxed));
 
     STACK_CHECK_START_REL(L, 0);
     // first, raise an error if the function is already known
@@ -420,8 +420,8 @@ static void update_lookup_entry( DEBUGSPEW_PARAM_COMMA( Universe* U) lua_State*
         lua_rawseti( L, fqn, _depth);                                                       // ... {bfc} k
     }
     -- _depth;
-    STACK_CHECK( L, -1);
-    DEBUGSPEW_CODE( -- U->debugspew_indent_depth);
+    STACK_CHECK(L, -1);
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_sub(1, std::memory_order_relaxed));
 }
 
 // #################################################################################################
@@ -435,8 +435,8 @@ static void populate_func_lookup_table_recur(DEBUGSPEW_PARAM_COMMA(Universe* U)
     int const cache = _ctx_base + 2;
     // we need to remember subtables to process them after functions encountered at the current depth (breadth-first search)
     int const breadth_first_cache = lua_gettop( L) + 1;
-    DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "populate_func_lookup_table_recur()\n" INDENT_END));
-    DEBUGSPEW_CODE( ++ U->debugspew_indent_depth);
+    DEBUGSPEW_CODE(fprintf( stderr, INDENT_BEGIN "populate_func_lookup_table_recur()\n" INDENT_END));
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_add(1, std::memory_order_relaxed));
 
     STACK_GROW( L, 6);
     // slot _i contains a table where we search for functions (or a full userdata with a metatable)
@@ -457,8 +457,8 @@ static void populate_func_lookup_table_recur(DEBUGSPEW_PARAM_COMMA(Universe* U)
     STACK_CHECK( L, 0);
     if( visit_count > 0)
     {
-        DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "already visited\n" INDENT_END));
-        DEBUGSPEW_CODE( -- U->debugspew_indent_depth);
+        DEBUGSPEW_CODE(fprintf( stderr, INDENT_BEGIN "already visited\n" INDENT_END));
+        DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_sub(1, std::memory_order_relaxed));
         return;
     }
 
@@ -513,7 +513,7 @@ static void populate_func_lookup_table_recur(DEBUGSPEW_PARAM_COMMA(Universe* U)
     {
         DEBUGSPEW_CODE( char const* key = (lua_type( L, -2) == LUA_TSTRING) ? lua_tostring( L, -2) : "not a string");
         DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "table '%s'\n" INDENT_END, key));
-        DEBUGSPEW_CODE( ++ U->debugspew_indent_depth);
+        DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_add(1, std::memory_order_relaxed));
         // un-visit this table in case we do need to process it
         lua_pushvalue( L, -1);                                                                  // ... {_i} {bfc} k {} {}
         lua_rawget( L, cache);                                                                  // ... {_i} {bfc} k {} n
@@ -536,7 +536,7 @@ static void populate_func_lookup_table_recur(DEBUGSPEW_PARAM_COMMA(Universe* U)
         populate_func_lookup_table_recur( DEBUGSPEW_PARAM_COMMA( U) L, _ctx_base, lua_gettop( L), _depth);
         lua_pop( L, 1);                                                                         // ... {_i} {bfc} k
         STACK_CHECK( L, 2);
-        DEBUGSPEW_CODE( -- U->debugspew_indent_depth);
+        DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_sub(1, std::memory_order_relaxed));
     }
     // remove table name from fqn stack
     lua_pushnil( L);                                                                          // ... {_i} {bfc} nil
@@ -546,7 +546,7 @@ static void populate_func_lookup_table_recur(DEBUGSPEW_PARAM_COMMA(Universe* U)
     lua_pop( L, 1);                                                                           // ... {_i}
     STACK_CHECK( L, 0);
     // we are done                                                                            // ... {_i} {bfc}
-    DEBUGSPEW_CODE( -- U->debugspew_indent_depth);
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_sub(1, std::memory_order_relaxed));
 }
 
 // #################################################################################################
@@ -561,7 +561,7 @@ void populate_func_lookup_table( lua_State* L, int _i, char const* name_)
     int start_depth = 0;
     DEBUGSPEW_CODE( Universe* U = universe_get( L));
     DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "%p: populate_func_lookup_table('%s')\n" INDENT_END, L, name_ ? name_ : "nullptr"));
-    DEBUGSPEW_CODE( ++ U->debugspew_indent_depth);
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_add(1, std::memory_order_relaxed));
     STACK_GROW( L, 3);
     STACK_CHECK_START_REL(L, 0);
     LOOKUP_REGKEY.pushValue(L);                                                      // {}
@@ -612,7 +612,7 @@ void populate_func_lookup_table( lua_State* L, int _i, char const* name_)
         (void) luaL_error( L, "unsupported module type %s", lua_typename( L, lua_type( L, in_base)));
     }
     STACK_CHECK( L, 0);
-    DEBUGSPEW_CODE( -- U->debugspew_indent_depth);
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_sub(1, std::memory_order_relaxed));
 }
 
 // #################################################################################################
@@ -1774,10 +1774,10 @@ static bool inter_copy_function(Universe* U, lua_State* L2, int L2_cache_i, lua_
     }
     else // regular function
     {
-        DEBUGSPEW_CODE( fprintf( stderr, "FUNCTION %s\n", upName_));
-        DEBUGSPEW_CODE( ++ U->debugspew_indent_depth);
+        DEBUGSPEW_CODE(fprintf( stderr, "FUNCTION %s\n", upName_));
+        DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_add(1, std::memory_order_relaxed));
         copy_cached_func( U, L2, L2_cache_i, L, source_i_, mode_, upName_);                                      // ... f
-        DEBUGSPEW_CODE( -- U->debugspew_indent_depth);
+        DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_sub(1, std::memory_order_relaxed));
     }
     STACK_CHECK( L2, 1);
     STACK_CHECK( L, 0);
@@ -1868,7 +1868,7 @@ bool inter_copy_one(Universe* U, lua_State* L2, int L2_cache_i, lua_State* L, in
     STACK_CHECK_START_REL(L2, 0);                                                      // L                          // L2
 
     DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "inter_copy_one()\n" INDENT_END));
-    DEBUGSPEW_CODE( ++ U->debugspew_indent_depth);
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_add(1, std::memory_order_relaxed));
     DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "%s %s: " INDENT_END, lua_type_names[val_type], vt_names[static_cast<int>(vt_)]));
 
     // Non-POD can be skipped if its metatable contains { __lanesignore = true }
@@ -1967,7 +1967,7 @@ bool inter_copy_one(Universe* U, lua_State* L2, int L2_cache_i, lua_State* L, in
         break;
     }
 
-    DEBUGSPEW_CODE( -- U->debugspew_indent_depth);
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_sub(1, std::memory_order_relaxed));
 
     STACK_CHECK( L2, ret ? 1 : 0);
     STACK_CHECK( L, 0);
@@ -1991,13 +1991,13 @@ int luaG_inter_copy(Universe* U, lua_State* L, lua_State* L2, int n, LookupMode
     bool copyok{ true };
 
     DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "luaG_inter_copy()\n" INDENT_END));
-    DEBUGSPEW_CODE( ++ U->debugspew_indent_depth);
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_add(1, std::memory_order_relaxed));
 
     if( n > top_L)
     {
         // requesting to copy more than is available?
         DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "nothing to copy()\n" INDENT_END));
-        DEBUGSPEW_CODE( -- U->debugspew_indent_depth);
+        DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_sub(1, std::memory_order_relaxed));
         return -1;
     }
 
@@ -2026,7 +2026,7 @@ int luaG_inter_copy(Universe* U, lua_State* L, lua_State* L2, int n, LookupMode
     }
     STACK_CHECK( L, 0);
 
-    DEBUGSPEW_CODE( -- U->debugspew_indent_depth);
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_sub(1, std::memory_order_relaxed));
 
     if( copyok)
     {
@@ -2051,54 +2051,57 @@ int luaG_inter_move(Universe* U, lua_State* L, lua_State* L2, int n, LookupMode
     return ret;
 }
 
-int luaG_inter_copy_package( Universe* U, lua_State* L, lua_State* L2, int package_idx_, LookupMode mode_)
+int luaG_inter_copy_package(Universe* U, lua_State* L, lua_State* L2, int package_idx_, LookupMode mode_)
 {
-    DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "luaG_inter_copy_package()\n" INDENT_END));
-    DEBUGSPEW_CODE( ++ U->debugspew_indent_depth);
+    DEBUGSPEW_CODE(fprintf(stderr, INDENT_BEGIN "luaG_inter_copy_package()\n" INDENT_END));
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_add(1, std::memory_order_relaxed));
     // package
     STACK_CHECK_START_REL(L, 0);
     STACK_CHECK_START_REL(L2, 0);
-    package_idx_ = lua_absindex( L, package_idx_);
-    if( lua_type( L, package_idx_) != LUA_TTABLE)
+    package_idx_ = lua_absindex(L, package_idx_);
+    if (lua_type(L, package_idx_) != LUA_TTABLE)
     {
-        lua_pushfstring( L, "expected package as table, got %s", luaL_typename( L, package_idx_));
-        STACK_CHECK( L, 1);
+        lua_pushfstring(L, "expected package as table, got %s", luaL_typename(L, package_idx_));
+        STACK_CHECK(L, 1);
         // raise the error when copying from lane to lane, else just leave it on the stack to be raised later
         return (mode_ == LookupMode::LaneBody) ? lua_error(L) : 1;
     }
-    lua_getglobal( L2, "package");
-    if( !lua_isnil( L2, -1)) // package library not loaded: do nothing
+    lua_getglobal(L2, "package");
+    if (!lua_isnil(L2, -1)) // package library not loaded: do nothing
     {
-        int i;
         // package.loaders is renamed package.searchers in Lua 5.2
         // but don't copy it anyway, as the function names change depending on the slot index!
         // users should provide an on_state_create function to setup custom loaders instead
         // don't copy package.preload in keeper states (they don't know how to translate functions)
         char const* entries[] = { "path", "cpath", (mode_ == LookupMode::LaneBody) ? "preload" : nullptr /*, (LUA_VERSION_NUM == 501) ? "loaders" : "searchers"*/, nullptr };
-        for( i = 0; entries[i]; ++ i)
+        for (char const* const entry : entries)
         {
-            DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "package.%s\n" INDENT_END, entries[i]));
-            lua_getfield( L, package_idx_, entries[i]);
-            if( lua_isnil( L, -1))
+            if (!entry)
+            {
+                continue;
+            }
+            DEBUGSPEW_CODE(fprintf(stderr, INDENT_BEGIN "package.%s\n" INDENT_END, entry));
+            lua_getfield(L, package_idx_, entry);
+            if (lua_isnil(L, -1))
             {
-                lua_pop( L, 1);
+                lua_pop(L, 1);
             }
             else
             {
-                DEBUGSPEW_CODE( ++ U->debugspew_indent_depth);
-                luaG_inter_move( U, L, L2, 1, mode_); // moves the entry to L2
-                DEBUGSPEW_CODE( -- U->debugspew_indent_depth);
-                lua_setfield( L2, -2, entries[i]); // set package[entries[i]]
+                DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_add(1, std::memory_order_relaxed));
+                luaG_inter_move(U, L, L2, 1, mode_); // moves the entry to L2
+                DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_sub(1, std::memory_order_relaxed));
+                lua_setfield(L2, -2, entry); // set package[entry]
             }
         }
     }
     else
     {
-        DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "'package' not loaded, nothing to do\n" INDENT_END));
+        DEBUGSPEW_CODE(fprintf(stderr, INDENT_BEGIN "'package' not loaded, nothing to do\n" INDENT_END));
     }
-    lua_pop( L2, 1);
-    STACK_CHECK( L2, 0);
-    STACK_CHECK( L, 0);
-    DEBUGSPEW_CODE( -- U->debugspew_indent_depth);
+    lua_pop(L2, 1);
+    STACK_CHECK(L2, 0);
+    STACK_CHECK(L, 0);
+    DEBUGSPEW_CODE(U->debugspew_indent_depth.fetch_sub(1, std::memory_order_relaxed));
     return 0;
 }
diff --git a/src/universe.h b/src/universe.h
index 6a65888..38885cb 100644
--- a/src/universe.h
+++ b/src/universe.h
@@ -158,13 +158,13 @@ struct Universe
     std::atomic<lua_Integer> next_mt_id{ 1 };
 
 #if USE_DEBUG_SPEW()
-    int debugspew_indent_depth{ 0 };
+    std::atomic<int> debugspew_indent_depth{ 0 };
 #endif // USE_DEBUG_SPEW()
 
     Lane* volatile selfdestruct_first{ nullptr };
     // After a lane has removed itself from the chain, it still performs some processing.
     // The terminal desinit sequence should wait for all such processing to terminate before force-killing threads
-    int volatile selfdestructing_count{ 0 };
+    std::atomic<int> selfdestructing_count{ 0 };
 };
 
 // ################################################################################################