X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/2895b2413e1efc17e3a42047c85a4917f1114708..898ef97fcc2d19b6aa3659ffadc59c6a47996c8e:/src/bindings/lua/simgrid_lua.c

diff --git a/src/bindings/lua/simgrid_lua.c b/src/bindings/lua/simgrid_lua.c
index e919383643..6e50eb9a9a 100644
--- a/src/bindings/lua/simgrid_lua.c
+++ b/src/bindings/lua/simgrid_lua.c
@@ -13,7 +13,9 @@
 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(lua, bindings, "Lua Bindings");
 
 #define TASK_MODULE_NAME "simgrid.task"
+#define COMM_MODULE_NAME "simgrid.comm"
 #define HOST_MODULE_NAME "simgrid.host"
+#define PROCESS_MODULE_NAME "simgrid.process"
 // Surf (bypass XML)
 #define LINK_MODULE_NAME "simgrid.link"
 #define ROUTE_MODULE_NAME "simgrid.route"
@@ -21,44 +23,18 @@ XBT_LOG_NEW_DEFAULT_SUBCATEGORY(lua, bindings, "Lua Bindings");
 
 static lua_State* sglua_maestro_state;
 
+static const char* msg_errors[] = {
+    NULL,
+    "timeout",
+    "transfer failure",
+    "host failure",
+    "task canceled"
+};
+
 int luaopen_simgrid(lua_State *L);
 static void register_c_functions(lua_State *L);
 static int run_lua_code(int argc, char **argv);
 
-
-/**
- * \brief Like luaL_checkudata, with additional debug logs.
- *
- * This function is for debugging purposes only.
- *
- * \param L a lua state
- * \param ud index of the userdata to check in the stack
- * \param tname key of the metatable of this userdata in the registry
- */
-static void* my_checkudata(lua_State* L, int ud, const char* tname)
-{
-  XBT_DEBUG("Checking the userdata: ud = %d", ud);
-  sglua_stack_dump("my_checkudata: ", L);
-  void* p = lua_touserdata(L, ud);
-  lua_getfield(L, LUA_REGISTRYINDEX, tname);
-  const void* correct_mt = lua_topointer(L, -1);
-
-  int has_mt = lua_getmetatable(L, ud);
-  XBT_DEBUG("Checking the userdata: has metatable ? %d", has_mt);
-  const void* actual_mt = NULL;
-  if (has_mt) {
-    actual_mt = lua_topointer(L, -1);
-    lua_pop(L, 1);
-  }
-  XBT_DEBUG("Checking the task's metatable: expected %p, found %p", correct_mt, actual_mt);
-  sglua_stack_dump("my_checkudata: ", L);
-
-  if (p == NULL || !lua_getmetatable(L, ud) || !lua_rawequal(L, -1, -2))
-    luaL_typerror(L, ud, tname);
-  lua_pop(L, 2);
-  return p;
-}
-
 /* ********************************************************************************* */
 /*                                simgrid.task API                                   */
 /* ********************************************************************************* */
@@ -96,6 +72,12 @@ static m_task_t sglua_checktask(lua_State* L, int index)
  * - Argument 2 (number): computation size
  * - Argument 3 (number): communication size
  * - Return value (task): the task created
+ *
+ * A Lua task is a regular table with a full userdata inside, and both share
+ * the same metatable. For the regular table, the metatable allows OO-style
+ * writing such as your_task:send(someone).
+ * For the userdata, the metatable is used to check its type.
+ * TODO: make the task name an optional last parameter
  */
 static int l_task_new(lua_State* L)
 {
@@ -110,6 +92,10 @@ static int l_task_new(lua_State* L)
 
   lua_newtable(L);
                                   /* task */
+  luaL_getmetatable(L, TASK_MODULE_NAME);
+                                  /* task mt */
+  lua_setmetatable(L, -2);
+                                  /* task */
   m_task_t* lua_task = (m_task_t*) lua_newuserdata(L, sizeof(m_task_t));
                                   /* task ctask */
   *lua_task = msg_task;
@@ -145,7 +131,7 @@ static int l_task_get_name(lua_State* L)
  * - Argument 1 (task): a task
  * - Return value (number): computation duration of this task
  */
-static int l_task_computation_duration(lua_State* L)
+static int l_task_get_computation_duration(lua_State* L)
 {
   m_task_t task = sglua_checktask(L, 1);
   lua_pushnumber(L, MSG_task_get_compute_duration(task));
@@ -158,14 +144,94 @@ static int l_task_computation_duration(lua_State* L)
  * \return number of values returned to Lua
  *
  * - Argument 1 (task): the task to execute
- * - Return value (number): error code
+ * - Return value (nil or string): nil if the task was successfully executed,
+ * or an error string in case of failure, which may be "task canceled" or
+ * "host failure"
  */
 static int l_task_execute(lua_State* L)
 {
   m_task_t task = sglua_checktask(L, 1);
-  int res = MSG_task_execute(task);
-  lua_pushnumber(L, res);
-  return 1;
+  MSG_error_t res = MSG_task_execute(task);
+
+  if (res == MSG_OK) {
+    return 0;
+  }
+  else {
+    lua_pushstring(L, msg_errors[res]);
+    return 1;
+  }
+}
+
+/**
+ * \brief Pops the Lua task on top of the stack and registers it so that a
+ * receiver can retrieve it later knowing the C task.
+ *
+ * After calling this function, you can send the C task to someone and he
+ * will be able to also get the corresponding Lua task.
+ *
+ * \param L a lua state
+ */
+static void task_register(lua_State* L) {
+
+  m_task_t task = sglua_checktask(L, -1);
+                                  /* ... task */
+  /* put in the C task a ref to the lua task so that the receiver finds it */
+  unsigned long ref = luaL_ref(L, LUA_REGISTRYINDEX);
+                                  /* ... */
+  MSG_task_set_data(task, (void*) ref);
+}
+
+/**
+ * \brief Pushes onto the stack the Lua task corresponding to a C task.
+ *
+ * The Lua task must have been previously registered with task_register so
+ * that it can be retrieved knowing the C task.
+ *
+ * \param L a lua state
+ * \param task a C task
+ */
+static void task_unregister(lua_State* L, m_task_t task) {
+
+                                  /* ... */
+  /* the task is in my registry, put it onto my stack */
+  unsigned long ref = (unsigned long) MSG_task_get_data(task);
+  lua_rawgeti(L, LUA_REGISTRYINDEX, ref);
+                                  /* ... task */
+  luaL_unref(L, LUA_REGISTRYINDEX, ref);
+  MSG_task_set_data(task, NULL);
+}
+
+/**
+ * \brief When a C task has been received, retrieves the corresponding Lua
+ * task from the sender and pushes it onto the receiver's stack.
+ *
+ * This function should be called from the receiver process.
+ *
+ * \param dst the receiver
+ * \param task the task just received
+ */
+static void task_copy(lua_State* dst, m_task_t task) {
+
+  m_process_t src_proc = MSG_task_get_sender(task);
+  lua_State* src = MSG_process_get_data(src_proc);
+
+                                  /* src: ...
+                                     dst: ... */
+  task_unregister(src, task);
+                                  /* src: ... task */
+  sglua_copy_value(src, dst);
+                                  /* src: ... task
+                                     dst: ... task */
+
+  /* the receiver is the owner of the task and may destroy it:
+   * make the C task NULL on the sender side so that it doesn't garbage
+   * collect it */
+  lua_getfield(src, -1, "__simgrid_task");
+                                  /* src: ... task ctask */
+  m_task_t* udata = (m_task_t*) luaL_checkudata(src, -1, TASK_MODULE_NAME);
+  *udata = NULL;
+  lua_pop(src, 2);
+                                  /* src: ... */
 }
 
 /**
@@ -174,50 +240,95 @@ static int l_task_execute(lua_State* L)
  * \return number of values returned to Lua
  *
  * - Argument 1 (task): the task to send
- * - Argument 2 (string): mailbox
+ * - Argument 2 (string or compatible): mailbox name, as a real string or any
+ * type convertible to string (numbers always are)
+ * - Return values (nil or string): nil if the communication was successful,
+ * or an error string in case of failure, which may be "timeout",
+ * "host failure" or "transfer failure"
  */
 static int l_task_send(lua_State* L)
 {
   m_task_t task = sglua_checktask(L, 1);
   const char* mailbox = luaL_checkstring(L, 2);
-                                  /* task mailbox */
+                                  /* task mailbox ... */
   lua_settop(L, 1);
                                   /* task */
-  /* copy my stack into the task, so that the receiver can copy the lua task */
-  MSG_task_set_data(task, L);
+  task_register(L);
+                                  /* -- */
   MSG_error_t res = MSG_task_send(task, mailbox);
-  while (MSG_task_get_data(task) != NULL) {
-    /* don't mess up with my stack: the receiver didn't copy the data yet */
-    MSG_process_sleep(0);
-  }
 
   if (res == MSG_OK) {
-    /* the receiver is the owner of the task and may destroy it:
-     * remove the C task on my side so that I don't garbage collect it */
-    lua_getfield(L, 1, "__simgrid_task");
-                                  /* task ctask */
-    m_task_t* udata = (m_task_t*) luaL_checkudata(L, -1, TASK_MODULE_NAME);
-    *udata = NULL;
-    lua_pop(L, 1);
-                                  /* task */
+    return 0;
   }
   else {
-    switch (res) {
-    case MSG_TIMEOUT:
-      XBT_DEBUG("MSG_task_send failed : Timeout");
-      break;
-    case MSG_TRANSFER_FAILURE:
-      XBT_DEBUG("MSG_task_send failed : Transfer Failure");
-      break;
-    case MSG_HOST_FAILURE:
-      XBT_DEBUG("MSG_task_send failed : Host Failure ");
-      break;
-    default:
-      XBT_ERROR
-          ("MSG_task_send failed : Unexpected error , please report this bug");
-      break;
-    }
+    /* the communication has failed, I'm still the owner of the task */
+    task_unregister(L, task);
+                                  /* task */
+    lua_pushstring(L, msg_errors[res]);
+                                  /* task error */
+    return 1;
   }
+}
+
+/**
+ * \brief Sends a task on a mailbox.
+ * \param L a Lua state
+ * \return number of values returned to Lua
+ *
+ * This is a non-blocking function: use simgrid.comm.wait() or
+ * simgrid.comm.test() to end the communication.
+ *
+ * - Argument 1 (task): the task to send
+ * - Argument 2 (string or compatible): mailbox name, as a real string or any
+ * type convertible to string (numbers always are)
+ * - Return value (comm): a communication object to be used later with wait or test
+ */
+static int l_task_isend(lua_State* L)
+{
+  m_task_t task = sglua_checktask(L, 1);
+  const char* mailbox = luaL_checkstring(L, 2);
+                                  /* task mailbox ... */
+  lua_settop(L, 1);
+                                  /* task */
+  task_register(L);
+                                  /* -- */
+  msg_comm_t comm = MSG_task_isend(task, mailbox);
+
+  msg_comm_t* userdata = (msg_comm_t*) lua_newuserdata(L, sizeof(msg_comm_t));
+                                  /* comm */
+  *userdata = comm;
+  luaL_getmetatable(L, COMM_MODULE_NAME);
+                                  /* comm mt */
+  lua_setmetatable(L, -2);
+                                  /* comm */
+  return 1;
+}
+
+/**
+ * \brief Sends a task on a mailbox on a best effort way (detached send).
+ * \param L a Lua state
+ * \return number of values returned to Lua
+ *
+ * Like simgrid.task.isend, this is a non-blocking function.
+ * You can use this function if you don't care about when the communication
+ * ends and whether it succeeds.
+ * FIXME: isn't this equivalent to calling simgrid.task.isend() and ignoring
+ * the result?
+ *
+ * - Argument 1 (task): the task to send
+ * - Argument 2 (string or compatible): mailbox name, as a real string or any
+ * type convertible to string (numbers always are)
+ */
+static int l_task_dsend(lua_State* L)
+{
+  m_task_t task = sglua_checktask(L, 1);
+  const char* mailbox = luaL_checkstring(L, 2);
+                                  /* task mailbox ... */
+  lua_settop(L, 1);
+                                  /* task */
+  task_register(L);
+                                  /* -- */
+  MSG_task_dsend(task, mailbox, NULL);
   return 0;
 }
 
@@ -226,18 +337,19 @@ static int l_task_send(lua_State* L)
  * \param L a Lua state
  * \return number of values returned to Lua
  *
- * - Argument 1 (string): mailbox
+ * - Argument 1 (string or compatible): mailbox name, as a real string or any
+ * type convertible to string (numbers always are)
  * - Argument 2 (number, optional): timeout (default is no timeout)
- * - Return value (task/nil): the task received or nil if the communication
- * has failed
+ * - Return values (task or nil + string): the task received, or nil plus an
+ * error message if the communication has failed
  */
-static int l_task_recv(lua_State *L)
+static int l_task_recv(lua_State* L)
 {
   m_task_t task = NULL;
   const char* mailbox = luaL_checkstring(L, 1);
   int timeout;
   if (lua_gettop(L) >= 2) {
-                                  /* mailbox timeout */
+                                  /* mailbox timeout ... */
     timeout = luaL_checknumber(L, 2);
   }
   else {
@@ -245,46 +357,64 @@ static int l_task_recv(lua_State *L)
     timeout = -1;
     /* no timeout by default */
   }
-  lua_settop(L, 0);
-                                  /* -- */
+                                  /* mailbox ... */
   MSG_error_t res = MSG_task_receive_with_timeout(&task, mailbox, timeout);
 
   if (res == MSG_OK) {
-    /* copy the data directly from sender's stack */
-    lua_State* sender_stack = MSG_task_get_data(task);
-    sglua_copy_value(sender_stack, L);
-                                  /* task */
-    MSG_task_set_data(task, NULL);
+    task_copy(L, task);
+                                  /* mailbox ... task */
+    return 1;
   }
   else {
-    switch (res) {
-    case MSG_TIMEOUT:
-      XBT_DEBUG("MSG_task_receive failed : Timeout");
-      break;
-    case MSG_TRANSFER_FAILURE:
-      XBT_DEBUG("MSG_task_receive failed : Transfer Failure");
-      break;
-    case MSG_HOST_FAILURE:
-      XBT_DEBUG("MSG_task_receive failed : Host Failure ");
-      break;
-    default:
-      XBT_ERROR("MSG_task_receive failed : Unexpected error , please report this bug");
-      break;
-    }
     lua_pushnil(L);
-                                  /* nil */
+                                  /* mailbox ... nil */
+    lua_pushstring(L, msg_errors[res]);
+                                  /* mailbox ... nil error */
+    return 2;
   }
-                                  /* task/nil */
+}
+
+/**
+ * \brief Asynchronously receives a task on a mailbox.
+ * \param L a Lua state
+ * \return number of values returned to Lua
+ *
+ * This is a non-blocking function: use simgrid.comm.wait() or
+ * simgrid.comm.test() to end the communication and get the task in case of
+ * success.
+ *
+ * - Argument 1 (string or compatible): mailbox name, as a real string or any
+ * type convertible to string (numbers always are)
+ * - Return value (comm): a communication object to be used later with wait or test
+ */
+
+static int l_task_irecv(lua_State* L)
+{
+  const char* mailbox = luaL_checkstring(L, 1);
+                                  /* mailbox ... */
+  m_task_t* task = xbt_new0(m_task_t, 1); // FIXME fix this leak
+  msg_comm_t comm = MSG_task_irecv(task, mailbox);
+
+  msg_comm_t* userdata = (msg_comm_t*) lua_newuserdata(L, sizeof(msg_comm_t));
+                                  /* mailbox ... comm */
+  *userdata = comm;
+  luaL_getmetatable(L, COMM_MODULE_NAME);
+                                  /* mailbox ... comm mt */
+  lua_setmetatable(L, -2);
+                                  /* mailbox ... comm */
   return 1;
 }
 
 static const luaL_reg task_functions[] = {
   {"new", l_task_new},
-  {"name", l_task_get_name},
-  {"computation_duration", l_task_computation_duration},
+  {"get_name", l_task_get_name},
+  {"get_computation_duration", l_task_get_computation_duration},
   {"execute", l_task_execute},
   {"send", l_task_send},
+  {"isend", l_task_isend},
+  {"dsend", l_task_dsend},
   {"recv", l_task_recv},
+  {"irecv", l_task_irecv},
   {NULL, NULL}
 };
 
@@ -322,12 +452,158 @@ static int l_task_tostring(lua_State* L)
   return 1;
 }
 
+/**
+ * \brief Metamethods of both a task table and the userdata inside it.
+ */
 static const luaL_reg task_meta[] = {
-  {"__gc", l_task_gc},
+  {"__gc", l_task_gc}, /* will be called only for userdata */
   {"__tostring", l_task_tostring},
   {NULL, NULL}
 };
 
+/* ********************************************************************************* */
+/*                                simgrid.comm API                                   */
+/* ********************************************************************************* */
+
+/**
+ * \brief Ensures that a value in the stack is a comm and returns it.
+ * \param L a Lua state
+ * \param index an index in the Lua stack
+ * \return the C comm
+ */
+static msg_comm_t sglua_checkcomm(lua_State* L, int index)
+{
+  msg_comm_t comm = *((msg_comm_t*) luaL_checkudata(L, index, COMM_MODULE_NAME));
+  lua_pop(L, 1);
+  return comm;
+}
+
+/**
+ * \brief Blocks the current process until a communication is finished.
+ * \param L a Lua state
+ * \return number of values returned to Lua
+ *
+ * - Argument 1 (comm): a comm (previously created by isend or irecv)
+ * - Argument 2 (number, optional): timeout (default is no timeout)
+ * - Return values (task or nil + string): in case of success, returns the task
+ * received if you are the receiver and nil if you are the sender. In case of
+ * failure, returns nil plus an error string.
+ */
+static int l_comm_wait(lua_State* L) {
+
+  msg_comm_t comm = sglua_checkcomm(L, 1);
+  double timeout = -1;
+  if (lua_gettop(L) >= 2) {
+    timeout = luaL_checknumber(L, 2);
+  }
+                                  /* comm ... */
+  MSG_error_t res = MSG_comm_wait(comm, timeout);
+
+  if (res == MSG_OK) {
+    m_task_t task = MSG_comm_get_task(comm);
+    if (MSG_task_get_sender(task) == MSG_process_self()) {
+      /* I'm the sender */
+      return 0;
+    }
+    else {
+      /* I'm the receiver: copy the Lua task from the sender */
+      task_copy(L, task);
+                                  /* comm ... task */
+      return 1;
+    }
+  }
+  else {
+    /* the communication has failed */
+    lua_pushnil(L);
+                                  /* comm ... nil */
+    lua_pushstring(L, msg_errors[res]);
+                                  /* comm ... nil error */
+    return 2;
+  }
+}
+
+/**
+ * @brief Returns whether a communication is finished.
+ *
+ * Unlike wait(), This function always returns immediately.
+ *
+ * - Argument 1 (comm): a comm (previously created by isend or irecv)
+ * - Return values (task/boolean or nil + string): if the communication is not
+ * finished, return false. If the communication is finished and was successful,
+ * returns the task received if you are the receiver or true if you are the
+ * sender. If the communication is finished and has failed, returns nil
+ * plus an error string.
+ */
+static int l_comm_test(lua_State* L) {
+
+  msg_comm_t comm = sglua_checkcomm(L, 1);
+                                  /* comm ... */
+  if (!MSG_comm_test(comm)) {
+    /* not finished yet */
+    lua_pushboolean(L, 0);
+                                  /* comm ... false */
+    return 1;
+  }
+  else {
+    /* finished but may have failed */
+    MSG_error_t res = MSG_comm_get_status(comm);
+
+    if (res == MSG_OK) {
+      m_task_t task = MSG_comm_get_task(comm);
+      if (MSG_task_get_sender(task) == MSG_process_self()) {
+        /* I'm the sender */
+        lua_pushboolean(L, 1);
+                                  /* comm ... true */
+        return 1;
+      }
+      else {
+        /* I'm the receiver: copy the Lua task from the sender */
+        task_copy(L, task);
+                                  /* comm ... task */
+        return 1;
+      }
+    }
+    else {
+      /* the communication has failed */
+      lua_pushnil(L);
+                                  /* comm ... nil */
+      lua_pushstring(L, msg_errors[res]);
+                                  /* comm ... nil error */
+      return 2;
+    }
+  }
+}
+
+static const luaL_reg comm_functions[] = {
+  {"wait", l_comm_wait},
+  {"test", l_comm_test},
+  /* TODO waitany, testany */
+  {NULL, NULL}
+};
+
+/**
+ * \brief Finalizes a comm userdata.
+ * \param L a Lua state
+ * \return number of values returned to Lua
+ *
+ * - Argument 1 (userdata): a comm
+ */
+static int l_comm_gc(lua_State* L)
+{
+                                  /* ctask */
+  msg_comm_t comm = *((msg_comm_t*) luaL_checkudata(L, 1, COMM_MODULE_NAME));
+  MSG_comm_destroy(comm);
+  return 0;
+}
+
+/**
+ * \brief Metamethods of the comm userdata.
+ */
+static const luaL_reg comm_meta[] = {
+  {"__gc", l_comm_gc},
+  {NULL, NULL}
+};
+
 /* ********************************************************************************* */
 /*                                simgrid.host API                                   */
 /* ********************************************************************************* */
@@ -482,7 +758,7 @@ static int l_host_sleep(lua_State *L)
 {
   int time = luaL_checknumber(L, 1);
   MSG_process_sleep(time);
-  return 1;
+  return 0;
 }
 
 /**
@@ -496,7 +772,7 @@ static int l_host_destroy(lua_State *L)
 {
   m_host_t ht = sglua_checkhost(L, 1);
   __MSG_host_destroy(ht);
-  return 1;
+  return 0;
 }
 
 static const luaL_reg host_functions[] = {
@@ -533,6 +809,46 @@ static const luaL_reg host_meta[] = {
   {0, 0}
 };
 
+/* ********************************************************************************* */
+/*                              simgrid.process API                                  */
+/* ********************************************************************************* */
+
+/**
+ * \brief Makes the current process sleep for a while.
+ * \param L a Lua state
+ * \return number of values returned to Lua
+ *
+ * - Argument 1 (number): duration of the sleep
+ * - Return value (nil or string): nil in everything went ok, or a string error
+ * if case of failure ("host failure")
+ */
+static int l_process_sleep(lua_State* L)
+{
+  double duration = luaL_checknumber(L, 1);
+  MSG_error_t res = MSG_process_sleep(duration);
+
+  switch (res) {
+
+  case MSG_OK:
+    return 0;
+
+  case MSG_HOST_FAILURE:
+    lua_pushliteral(L, "host failure");
+    return 1;
+
+  default:
+    xbt_die("Unexpected result of MSG_process_sleep: %d, please report this bug", res);
+  }
+}
+
+static const luaL_reg process_functions[] = {
+    {"sleep", l_process_sleep},
+    /* TODO: self, create, kill, suspend, is_suspended, resume, get_name,
+     * get_pid, get_ppid, migrate
+     */
+    {NULL, NULL}
+};
+
 /* ********************************************************************************* */
 /*                           lua_stub_generator functions                            */
 /* ********************************************************************************* */
@@ -628,9 +944,9 @@ static const luaL_reg platf_functions[] = {
  *
  * - Argument 1 (string): name of the deployment file to load
  */
-static int launch_application(lua_State * L)
-{
-  const char *file = luaL_checkstring(L, 1);
+static int launch_application(lua_State* L) {
+
+  const char* file = luaL_checkstring(L, 1);
   MSG_function_register_default(run_lua_code);
   MSG_launch_application(file);
   return 0;
@@ -643,9 +959,9 @@ static int launch_application(lua_State * L)
  *
  * - Argument 1 (string): name of the platform file to load
  */
-static int create_environment(lua_State * L)
-{
-  const char *file = luaL_checkstring(L, 1);
+static int create_environment(lua_State* L) {
+
+  const char* file = luaL_checkstring(L, 1);
   XBT_DEBUG("Loading environment file %s", file);
   MSG_create_environment(file);
   return 0;
@@ -658,9 +974,9 @@ static int create_environment(lua_State * L)
  *
  * - Argument 1 (string): the text to print
  */
-static int debug(lua_State * L)
-{
-  const char *str = luaL_checkstring(L, 1);
+static int debug(lua_State* L) {
+
+  const char* str = luaL_checkstring(L, 1);
   XBT_DEBUG("%s", str);
   return 0;
 }
@@ -672,9 +988,9 @@ static int debug(lua_State * L)
  *
  * - Argument 1 (string): the text to print
  */
-static int info(lua_State * L)
-{
-  const char *str = luaL_checkstring(L, 1);
+static int info(lua_State* L) {
+
+  const char* str = luaL_checkstring(L, 1);
   XBT_INFO("%s", str);
   return 0;
 }
@@ -684,18 +1000,31 @@ static int info(lua_State * L)
  * \param L a Lua state
  * \return number of values returned to Lua
  */
-static int run(lua_State * L)
-{
+static int run(lua_State*  L) {
+
   MSG_main();
   return 0;
 }
 
+/**
+ * \brief Returns the current simulated time.
+ * \param L a Lua state
+ * \return number of values returned to Lua
+ *
+ * - Return value (number): the simulated time
+ */
+static int get_clock(lua_State* L) {
+
+  lua_pushnumber(L, MSG_get_clock());
+  return 1;
+}
+
 /**
  * \brief Cleans the simulation.
  * \param L a Lua state
  * \return number of values returned to Lua
  */
-static int clean(lua_State * L)
+static int simgrid_gc(lua_State * L)
 {
   MSG_clean();
   return 0;
@@ -764,7 +1093,7 @@ static const luaL_Reg simgrid_functions[] = {
   {"debug", debug},
   {"info", info},
   {"run", run},
-  {"clean", clean},
+  {"get_clock", get_clock},
   /* short names */
   {"platform", create_environment},
   {"application", launch_application},
@@ -863,44 +1192,162 @@ lua_State* sglua_get_maestro(void) {
 }
 
 /**
- * \brief Makes the appropriate Simgrid functions available to the Lua world.
- * \param L a Lua world
+ * \brief Registers the task functions into the table simgrid.task.
+ *
+ * Also initialize the metatable of the task userdata type.
+ *
+ * \param L a lua state
  */
-void register_c_functions(lua_State *L) {
+static void register_task_functions(lua_State* L)
+{
+  /* create a table simgrid.task and fill it with task functions */
+  luaL_openlib(L, TASK_MODULE_NAME, task_functions, 0);
+                                  /* simgrid.task */
+
+  /* create the metatable for tasks, add it to the Lua registry */
+  luaL_newmetatable(L, TASK_MODULE_NAME);
+                                  /* simgrid.task mt */
+  /* fill the metatable */
+  luaL_openlib(L, NULL, task_meta, 0);
+                                  /* simgrid.task mt */
+  lua_pushvalue(L, -2);
+                                  /* simgrid.task mt simgrid.task */
+  /* metatable.__index = simgrid.task
+   * we put the task functions inside the task itself:
+   * this allows to write my_task:method(args) for
+   * simgrid.task.method(my_task, args) */
+  lua_setfield(L, -2, "__index");
+                                  /* simgrid.task mt */
+  lua_pop(L, 2);
+                                  /* -- */
+}
 
-  /* register the core C functions to lua */
-  luaL_register(L, "simgrid", simgrid_functions);
+/**
+ * \brief Registers the comm functions into the table simgrid.comm.
+ *
+ * Also initialize the metatable of the comm userdata type.
+ *
+ * \param L a lua state
+ */
+static void register_comm_functions(lua_State* L)
+{
+  /* create a table simgrid.com and fill it with com functions */
+  luaL_openlib(L, COMM_MODULE_NAME, comm_functions, 0);
+                                  /* simgrid.comm */
+
+  /* create the metatable for comms, add it to the Lua registry */
+  luaL_newmetatable(L, COMM_MODULE_NAME);
+                                  /* simgrid.comm mt */
+  /* fill the metatable */
+  luaL_openlib(L, NULL, comm_meta, 0);
+                                  /* simgrid.comm mt */
+  lua_pushvalue(L, -2);
+                                  /* simgrid.comm mt simgrid.comm */
+  /* metatable.__index = simgrid.comm
+   * we put the comm functions inside the comm itself:
+   * this allows to write my_comm:method(args) for
+   * simgrid.comm.method(my_comm, args) */
+  lua_setfield(L, -2, "__index");
+                                  /* simgrid.comm mt */
+  lua_pop(L, 2);
+                                  /* -- */
+}
 
-  /* register the task methods to lua */
-  luaL_openlib(L, TASK_MODULE_NAME, task_functions, 0);   // create methods table, add it to the globals
-  luaL_newmetatable(L, TASK_MODULE_NAME);       // create metatable for Task, add it to the Lua registry
-  luaL_openlib(L, 0, task_meta, 0);     // fill metatable
-  lua_pushliteral(L, "__index");
-  lua_pushvalue(L, -3);         // dup methods table
-  lua_rawset(L, -3);            // metatable.__index = methods
-  lua_pushliteral(L, "__metatable");
-  lua_pushvalue(L, -3);         // dup methods table
-  lua_rawset(L, -3);            // hide metatable:metatable.__metatable = methods
-  lua_pop(L, 1);                // drop metatable
-
-  /* register the hosts methods to lua */
+/**
+ * \brief Registers the host functions into the table simgrid.host.
+ *
+ * Also initialize the metatable of the host userdata type.
+ *
+ * \param L a lua state
+ */
+static void register_host_functions(lua_State* L)
+{
+  /* create a table simgrid.host and fill it with host functions */
   luaL_openlib(L, HOST_MODULE_NAME, host_functions, 0);
+                                  /* simgrid.host */
+
+  /* create the metatable for host, add it to the Lua registry */
   luaL_newmetatable(L, HOST_MODULE_NAME);
-  luaL_openlib(L, 0, host_meta, 0);
-  lua_pushliteral(L, "__index");
-  lua_pushvalue(L, -3);
-  lua_rawset(L, -3);
-  lua_pushliteral(L, "__metatable");
-  lua_pushvalue(L, -3);
-  lua_rawset(L, -3);
+                                  /* simgrid.host mt */
+  /* fill the metatable */
+  luaL_openlib(L, NULL, host_meta, 0);
+                                  /* simgrid.host mt */
+  lua_pushvalue(L, -2);
+                                  /* simgrid.host mt simgrid.host */
+  /* metatable.__index = simgrid.host
+   * we put the host functions inside the host userdata itself:
+   * this allows to write my_host:method(args) for
+   * simgrid.host.method(my_host, args) */
+  lua_setfield(L, -2, "__index");
+                                  /* simgrid.host mt */
+  lua_pop(L, 2);
+                                  /* -- */
+}
+
+/**
+ * \brief Registers the process functions into the table simgrid.process.
+ * \param L a lua state
+ */
+static void register_process_functions(lua_State* L)
+{
+  luaL_openlib(L, PROCESS_MODULE_NAME, process_functions, 0);
+                                  /* simgrid.process */
   lua_pop(L, 1);
+}
 
-  /* register the platform methods to lua */
+/**
+ * \brief Registers the platform functions into the table simgrid.platf.
+ * \param L a lua state
+ */
+static void register_platf_functions(lua_State* L)
+{
   luaL_openlib(L, PLATF_MODULE_NAME, platf_functions, 0);
-  luaL_newmetatable(L, PLATF_MODULE_NAME);
+                                  /* simgrid.platf */
   lua_pop(L, 1);
 }
 
+/**
+ * \brief Makes the core functions available to the Lua world.
+ * \param L a Lua world
+ */
+static void register_core_functions(lua_State *L)
+{
+  /* register the core C functions to lua */
+  luaL_register(L, "simgrid", simgrid_functions);
+                                  /* simgrid */
+
+  /* set a finalizer that cleans simgrid, by adding to the simgrid module a
+   * dummy userdata whose __gc metamethod calls MSG_clean() */
+  lua_newuserdata(L, sizeof(void*));
+                                  /* simgrid udata */
+  lua_newtable(L);
+                                  /* simgrid udata mt */
+  lua_pushcfunction(L, simgrid_gc);
+                                  /* simgrid udata mt simgrid_gc */
+  lua_setfield(L, -2, "__gc");
+                                  /* simgrid udata mt */
+  lua_setmetatable(L, -2);
+                                  /* simgrid udata */
+  lua_setfield(L, -2, "__simgrid_loaded");
+                                  /* simgrid */
+  lua_pop(L, 1);
+                                  /* -- */
+}
+
+/**
+ * \brief Creates the simgrid module and make it available to Lua.
+ * \param L a Lua world
+ */
+static void register_c_functions(lua_State *L)
+{
+  register_core_functions(L);
+  register_task_functions(L);
+  register_comm_functions(L);
+  register_host_functions(L);
+  register_process_functions(L);
+  register_platf_functions(L);
+}
+
 /**
  * \brief Runs a Lua function as a new simulated process.
  * \param argc number of arguments of the function
@@ -911,13 +1358,14 @@ static int run_lua_code(int argc, char **argv)
 {
   XBT_DEBUG("Run lua code %s", argv[0]);
 
+  /* create a new state, getting globals from maestro */
   lua_State *L = sglua_clone_maestro();
-  int res = 1;
+  MSG_process_set_data(MSG_process_self(), L);
 
   /* start the function */
   lua_getglobal(L, argv[0]);
   xbt_assert(lua_isfunction(L, -1),
-              "The lua function %s does not seem to exist", argv[0]);
+              "There is no Lua function with name `%s'", argv[0]);
 
   /* push arguments onto the stack */
   int i;
@@ -927,10 +1375,11 @@ static int run_lua_code(int argc, char **argv)
   /* call the function */
   _XBT_GNUC_UNUSED int err;
   err = lua_pcall(L, argc - 1, 1, 0);
-  xbt_assert(err == 0, "error running function `%s': %s", argv[0],
+  xbt_assert(err == 0, "Error running function `%s': %s", argv[0],
               lua_tostring(L, -1));
 
   /* retrieve result */
+  int res = 1;
   if (lua_isnumber(L, -1)) {
     res = lua_tonumber(L, -1);
     lua_pop(L, 1);              /* pop returned value */