Function _pftx_create_locked

components/lwp/lwp_futex.c:141–204

* @brief Creates and initializes a private futex * * @param[in] uaddr Pointer to the user-space address used as futex key * @param[in] lwp Pointer to the lightweight process structure * * @return rt_futex_t Returns pointer to created futex on success, NULL on failure * * @note This function allocates memory, creates a custom object, * adds it to the lwp user object tree, and initiali

 *       The created futex will be automatically destroyed when the lwp is freed.
 */
static rt_futex_t _pftx_create_locked(int *uaddr, struct rt_lwp *lwp)
{
    rt_futex_t futex = RT_NULL;
    struct rt_object *obj = RT_NULL;

    /**
     * Brief: Create a futex under current lwp
     *
     * Note: Critical Section
     * - lwp (READ; share with thread)
     */
    if (lwp)
    {
        futex = (rt_futex_t)rt_malloc(sizeof(struct rt_futex));
        if (futex)
        {
            /* Create a Private FuTeX (pftx) */
            obj = rt_custom_object_create("pftx", (void *)futex,
                                          _pftx_destroy_locked);
            if (!obj)
            {
                rt_free(futex);
                futex = RT_NULL;
            }
            else
            {
                /**
                 * Brief: Add futex to user object tree for resource recycling
                 *
                 * Note: Critical Section
                 * - lwp user object tree (RW; protected by API)
                 * - futex (if the adding is successful, others can find the
                 *   unready futex. However, only the lwp_free will do this,
                 *   and this is protected by the ref taken by the lwp thread
                 *   that the lwp_free will never execute at the same time)
                 */
                if (lwp_user_object_add(lwp, obj))
                {
                    /* this will call a _pftx_destroy_locked, but that's okay */
                    rt_object_delete(obj);
                    rt_free(futex);
                    futex = RT_NULL;
                }
                else
                {
                    futex->node.avl_key = (avl_key_t)uaddr;
                    futex->node.data = &lwp->address_search_head;
                    futex->custom_obj = obj;
                    futex->mutex = RT_NULL;
                    rt_list_init(&(futex->waiting_thread));

                    /**
                     * Brief: Insert into futex head
                     *
                     * Note: Critical Section
                     * - lwp address_search_head (RW; protected by caller)
                     */
                    lwp_avl_insert(&futex->node, &lwp->address_search_head);