Contiki, while loop, functions are not executed

Question

I have the following problem, my simulation results to be stuck in the while loop. In my opinion, the reason is that we cannot execute the recv_uc on mote 1.0 before the loop ends. However, is the mote 1.0 itself that calls

unicast_send(&my_conn, &addr);

which changes

value = true;

I need to avoid to be stuck in the while loop. This is the most important part of the code.

static void my_func(struct unicast_conn *c, const rimeaddr_t *addr){
  value = true;
...
}

static const struct unicast_callbacks my_call = {my_func};
//only mote 1 execute recv_uc
static void recv_uc(struct unicast_conn *c, const rimeaddr_t *from)
{
  my_msg_t mess_rec;
  rimeaddr_t addr;

  addr.u8[0]= from->u8[0];
  addr.u8[1]= from->u8[1];

  memcpy(&mess_rec, packetbuf_dataptr(), sizeof(mess_rec));
  ...
  packetbuf_copyfrom(&mess_rec, 16);
  unicast_send(&my_conn, &addr);
}

static const struct unicast_callbacks unicast_call = {recv_uc};

PROCESS_THREAD(sending_rand, ev, data)
{
...

PROCESS_BEGIN();
unicast_open(&unicast, 120, &unicast_call); //importante
unicast_open(&my_conn, 130, &my_call); //importante
...
addr.u8[0] = 1;
addr.u8[1] = 0;
if(!rimeaddr_cmp(&addr, &rimeaddr_node_addr)){
...
while(value == false){
  packetbuf_copyfrom(&mess, 16);
  unicast_send(&unicast, &addr);
}
}
PROCESS_END();
}

Thank you.

Answer 1

Contiki uses cooperative multithreading, so if your thread does not yield it will not be interrupted except for actual hardware interrupts. Since it is a while since I worked with Contiki I am not absolutely sure whether the network callbacks are executed in interrupt handlers or in a dedicated process in the main loop. If the latter is true this would explain why your process never left the waiting loop.

I would recommend replacing the while loop by the following:

while(value == false){
  packetbuf_copyfrom(&mess, 16);
  unicast_send(&unicast, &addr);
  PROCESS_YIELD(); // this allows other processes to run
}

Setting a timer may also be a good idea, depending on how often you want to send.