Best way to implement interthread communication in FreeRTOS? - checking the state of a lwIP cable

Question

I want to make a lwip cable on/off bulletproof with DHCP on and a TCP connection. Both solutions work ok but I don't know which one is the more sensible and right. (I am afraid of wrong context function calls)

• First solution:

I call:

tcpip_init(network_init, &net);

and then after that:

xTaskCreate(hc_task, ( signed portCHAR * ) "send hc",1536u, NULL, TCPIP_THREAD_PRIO, NULL);

So there are 2 threads the main lwIP thread and the hc_task thread. hc_task is:

static void hc_task(void *parameters)
{
    struct hc_message mes;
    mes.client_port_number = 4839;
    mes.host_addres = "192.168.1.183\0";
    mes.host_add[0] = 192;
    mes.host_add[1] = 168;
    mes.host_add[2] = 1;
    mes.host_add[3] = 183;
    mes.host_file = "test/data.php\0";
    mes.host_port_number = 80;
    mes.target = "http://192.168.1.183/test/data.php\0";

    transferEnd = 0;
    numberOfPacketsProc = 0;
    totalRecievedSize = 0;

    hc_send(&mes, 0);
    vTaskDelete(NULL);
}

hc_send does a TCP connection to some page to download it.

Then I have a polling timer with an interval of 2 seconds which checks PHY and reads the cable state:

if cable is on  -> ok
if cable is off -> call netif_set_link_down(pxNetIfInUse);

Now next time when the cable goes on I call:

netif_set_link_up(pxNetIfInUse);

I am guessing that is correct to call these functions in a timer interrupt.

• Second solution:

The second method is that the timer interrupt sends a message to the main lwip thread:

Link off -> res = sys_mbox_trypost(toOutput, &msg); 

The timer interrupt sends the main lwip thread a message to call either:

netif_set_link_up(pxNetIfInUse);

or:

netif_set_link_down(pxNetIfInUse); //(in lwip main thread)

I have a global variable to store the cable state (saved from that timer interrupt), and I check it in the main lwip thread to call the right function (link up or down).

So I am asking which solution is the better/right way to do it: in the timer interrupt call link down or up (these are lwip functions) OR the timer interrupt sends a message to main lwIP thread?

My configuration: Microprocessor LPC1768 - LAN8720 PHY - FreeRTOS 7.4 - lwip 1.4.1 - DHCP included - TCP/IP included

Answer 1

After some days in thanks to lwip user support (thanks to Pomeroy Marty, Sylvain Rochet, Richard and other who hellped me - link to debate) forum I came to answer:

In a timer call:

//link off
printf( "Interrupt LINK OFF\n"  );
iface_up = 0;
resultCall = tcpip_callback_with_block(tcp_set_link_status, NULL, 0);

//link on
printf("Interrupt LINK ON\n"  );
resultCall = tcpip_callback_with_block(tcp_set_link_status, NULL, 0);

So the function below will be executed in thread context of main lwip TCP/IP thread which is correct:

void tcp_set_link_status(void)
{
        if(cableState == 0)
        {
                printf("TCP callback printf set link down \n");
                netif_set_link_down(pxNetIfInUse);
        }
        else
        {
                printf("TCP callback Printf set link up \n");
                netif_set_link_up(pxNetIfInUse);
        }
}