core: clist without explicit thread

Right now the core component `clist` is a generic cyclic doubly-linked list.
In the core it is used in `tcb_t::rq_entry`.
Further it is used `net_if.c`.

This commit removes the member `clist_node_t::data` which stored the
pointer to the `tcb_t` instance of which the clist is already a member.
The needless member added `sizeof (int)` bytes to every instance of
`tcb_t`.

In `net_if.c` the clist was used in a type-punned way, so that the
change won't affect it.

core/include/clist.h

@@ -19,13 +19,29 @@
 #ifndef __CLIST_H
 #define __CLIST_H
 
+#include "kernel_macros.h"
+
+/**
+ * @def         clist_get_container(NODE, TYPE, MEMBER)
+ * @brief       Returns the container of the circular list
+ * @details     For a struct `TYPE` with a member `MEMBER`, which is a `clist_node_t`,
+ *              given a pointer `NODE` to `TYPE::MEMBER` this function returns a pointer
+ *              to the instance of `TYPE`.
+ * @details     E.g. for `struct my_struct_t { ...; clist_node_t n; ... } my_struct;`,
+ *              `&my_struct == clist_get_container(&my_struct.n, struct my_struct_t, n)`.
+ * @param[in]   NODE     pointer to a member
+ * @param[in]   TYPE     a type name (a struct or union), container of NODE
+ * @param[in]   MEMBER   name of the member of TYPE which NODE points to
+ * @return      Pointer to the container of NODE.
+ */
+#define clist_get_container(NODE, TYPE, MEMBER) container_of(NODE, TYPE, MEMBER)
+
 /**
  * @brief Structure representing a node in the clist.
  */
 typedef struct clist_node_t {
     struct clist_node_t *next;  /**< pointer to next node         */
     struct clist_node_t *prev;  /**< pointer to the previous node */
-    unsigned int data;          /**< holding data for this node   */
 } clist_node_t;
 
 /**

core/include/kernel_macros.h

@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2014 Freie Universität Berlin
+ *
+ * This file subject to the terms and conditions of the GNU Lesser General
+ * Public License. See the file LICENSE in the top level directory for more
+ * details.
+ */
+
+/**
+ * @addtogroup  core_util
+ * @{
+ *
+ * @file        kernel_macros.h
+ * @brief       common macros
+ *
+ * @author      René Kijewski
+ */
+
+#include <stddef.h>
+
+/**
+ * @def         container_of(PTR, TYPE, MEMBER)
+ * @brief       Returns the container of a pointer to a member.
+ * @details     For a struct `TYPE` with a member `MEMBER`,
+ *              given a pointer `PTR` to `TYPE::MEMBER` this function returns a pointer
+ *              to the instance of `TYPE`.
+ * @details     E.g. for `struct my_struct_t { ...; something_t n; ... } my_struct;`,
+ *              `&my_struct == container_of(&my_struct.n, struct my_struct_t, n)`.
+ * @param[in]   PTR      pointer to a member
+ * @param[in]   TYPE     a type name (a struct or union), container of PTR
+ * @param[in]   MEMBER   name of the member of TYPE which PTR points to
+ * @return      Pointer to the container of PTR.
+ */
+#if __STDC_VERSION__ >= 201112L
+#   define container_of(PTR, TYPE, MEMBER) \
+        (_Generic((PTR), \
+            const __typeof__ (((TYPE *) 0)->MEMBER) *: \
+                ((TYPE *) ((char *) (PTR) - offsetof(TYPE, MEMBER))), \
+            __typeof__ (((TYPE *) 0)->MEMBER) *: \
+                ((TYPE *) ((char *) (PTR) - offsetof(TYPE, MEMBER))) \
+        ))
+#elif defined __GNUC__
+#   define container_of(PTR, TYPE, MEMBER) \
+        (__extension__ ({ \
+            __extension__ const __typeof__ (((TYPE *) 0)->MEMBER) *__m____ = (PTR); \
+            ((TYPE *) ((char *) __m____ - offsetof(TYPE, MEMBER))); \
+        }))
+#else
+#   define container_of(PTR, TYPE, MEMBER) \
+        ((TYPE *) ((char *) (PTR) - offsetof(TYPE, MEMBER)))
+#endif
+
+/**
+ * @}
+ */

core/sched.c

@@ -87,10 +87,10 @@ void sched_run(void)
      * since the threading should not be started before at least the idle thread was started.
      */
     int nextrq = bitarithm_lsb(runqueue_bitcache);
-    clist_node_t next = *(sched_runqueues[nextrq]);
-    DEBUG("scheduler: first in queue: %s\n", ((tcb_t *)next.data)->name);
+    my_active_thread = clist_get_container(sched_runqueues[nextrq], tcb_t, rq_entry);
     clist_advance(&(sched_runqueues[nextrq]));
-    my_active_thread = (tcb_t *)next.data;
+    DEBUG("scheduler: first in queue: %s\n", my_active_thread->name);
+    sched_active_pid = (volatile int) my_active_thread->pid;
 
     kernel_pid_t my_next_pid = my_active_thread->pid;
 

core/thread.c

@@ -185,7 +185,6 @@ kernel_pid_t thread_create(char *stack, int stacksize, char priority, int flags,
     cb->priority = priority;
     cb->status = 0;
 
-    cb->rq_entry.data = (unsigned int) cb;
     cb->rq_entry.next = NULL;
     cb->rq_entry.prev = NULL;