Function _lwp_shmget

components/lwp/lwp_shm.c:109–190

Locate the shared memory through 'key' or create a new one. */

/* Locate the shared memory through 'key' or create a new one. */
static int _lwp_shmget(size_t key, size_t size, int create)
{
    int id = -1;
    struct lwp_avl_struct *node_key = 0;
    struct lwp_avl_struct *node_pa = 0;
    void *page_addr = 0;
    uint32_t bit = 0;

    /* try to locate the item with the key in the binary tree */
    node_key = lwp_avl_find(key, shm_tree_key);
    if (node_key)
    {
        return (struct lwp_shm_struct *)node_key->data - _shm_ary;   /* the index */
    }

    /* If there doesn't exist such an item and we're allowed to create one ... */
    if (create)
    {
        struct lwp_shm_struct* p;

        if (!size)
        {
            goto err;
        }

        id = _shm_id_alloc();
        if (id == -1)
        {
            goto err;
        }

        /* allocate pages up to 2's exponent to cover the required size */
        bit = rt_page_bits(size);
        page_addr = rt_pages_alloc_ext(bit, PAGE_ANY_AVAILABLE);   /* virtual address */
        if (!page_addr)
        {
            goto err;
        }

        /* initialize the shared memory structure */
        p = _shm_ary + id;
        p->addr = (size_t)page_addr;
        p->size = (1UL << (bit + ARCH_PAGE_SHIFT));
        p->ref = 0;
        p->key = key;
        p->mem_obj.get_name = get_shm_name;
        p->mem_obj.on_page_fault = on_shm_page_fault;
        p->mem_obj.on_varea_open = on_shm_varea_open;
        p->mem_obj.on_varea_close = on_shm_varea_close;
        p->mem_obj.hint_free = NULL;

        /* then insert it into the balancing binary tree */
        node_key = (struct lwp_avl_struct *)rt_malloc(sizeof(struct lwp_avl_struct) * 2);
        if (!node_key)
        {
            goto err;
        }
        node_key->avl_key = p->key;