关于MAC协议中的CSMA协议，Contiki操作系统里的

ZRRR

有大佬知道图片里的send_packet函数是如何调用transmit_packet_list函数的么，我看了半天send_packet函数没看到在哪调用的？？代码如下
/*---------------------------------------------------------------------------*/
static void
send_packet(mac_callback_t sent, void *ptr)
{
  struct rdc_buf_list *q;
  struct neighbor_queue *n;
  static uint16_t seqno;

  packetbuf_set_attr(PACKETBUF_ATTR_MAC_SEQNO, seqno++);

  /* If the packet is a broadcast, do not allocate a queue
     entry. Instead, just send it out.  */
  if(!rimeaddr_cmp(packetbuf_addr(PACKETBUF_ADDR_RECEIVER),
                   &rimeaddr_null)) {
    const rimeaddr_t *addr = packetbuf_addr(PACKETBUF_ADDR_RECEIVER);

    /* Look for the neighbor entry */
    n = neighbor_queue_from_addr(addr);
    if(n == NULL) {
      /* Allocate a new neighbor entry */
      n = memb_alloc(&neighbor_memb);
      if(n != NULL) {
        /* Init neighbor entry */
        rimeaddr_copy(&n->addr, addr);
        n->transmissions = 0;
        n->collisions = 0;
        n->deferrals = 0;
        /* Init packet list for this neighbor */
        LIST_STRUCT_INIT(n, queued_packet_list);
        /* Add neighbor to the list */
        list_add(neighbor_list, n);
      }
    }

    if(n != NULL) {
      /* Add packet to the neighbor's queue */
         q = memb_alloc(&packet_memb);      if(q != NULL) {
        q->ptr = memb_alloc(&metadata_memb);
        if(q->ptr != NULL) {
          q->buf = queuebuf_new_from_packetbuf();
          if(q->buf != NULL) {
            struct qbuf_metadata *metadata = (struct qbuf_metadata *)q->ptr;
            /* Neighbor and packet successfully allocated */
            if(packetbuf_attr(PACKETBUF_ATTR_MAX_MAC_TRANSMISSIONS) == 0) {
              /* Use default configuration for max transmissions */
              metadata->max_transmissions = CSMA_MAX_MAC_TRANSMISSIONS;
            } else {
              metadata->max_transmissions =
                  packetbuf_attr(PACKETBUF_ATTR_MAX_MAC_TRANSMISSIONS);
            }
            metadata->sent = sent;
            metadata->cptr = ptr;

            if(packetbuf_attr(PACKETBUF_ATTR_PACKET_TYPE) ==
                PACKETBUF_ATTR_PACKET_TYPE_ACK) {
//              list_init(n->queued_packet_list);
                                                  list_push(n->queued_packet_list, q);
            } else {
//                                                        list_init(n->queued_packet_list);
              list_add(n->queued_packet_list, q);
            }

            /* If q is the first packet in the neighbor's queue, send asap */
            if(list_head(n->queued_packet_list) == q) {
              ctimer_set(&n->transmit_timer, 0, transmit_packet_list, n);//
            }
            return;
//                                                transmit_packet_list(ptr);
          }
          memb_free(&metadata_memb, q->ptr);
          PRINTF("csma: could not allocate queuebuf, dropping packet\n");
        }
        memb_free(&packet_memb, q);
        PRINTF("csma: could not allocate queuebuf, dropping packet\n");
      }
      /* The packet allocation failed. Remove and free neighbor entry if empty. */
      if(list_length(n->queued_packet_list) == 0) {
        list_remove(neighbor_list, n);
        memb_free(&neighbor_memb, n);
      }
      PRINTF("csma: could not allocate packet, dropping packet\n");
    } else {
      PRINTF("csma: could not allocate neighbor, dropping packet\n");
    }
    mac_call_sent_callback(sent, ptr, MAC_TX_ERR, 1);
  } else {
    PRINTF("csma: send broadcast\n");
    NETSTACK_RDC.send(sent, ptr);
  }
}
/*---------------------------------------------------------------------------*/
static void
transmit_packet_list(void *ptr)
{
  struct neighbor_queue *n = ptr;
  if(n) {
    struct rdc_buf_list *q = list_head(n->queued_packet_list);
    if(q != NULL) {
      PRINTF("csma: preparing number %d %p, queue len %d\n", n->transmissions, q,
          list_length(n->queued_packet_list));
      /* Send packets in the neighbor's list */
      NETSTACK_RDC.send_list(packet_sent, n, q);
    }
  }
}
/*---------------------------------------------------------------------------*/