beremiz

Modbus plugin: reformat code, and add comment.

2020-08-13, Mario de Sousa
4dd67aa45855
Parents c79c5d49ba34
Children f9d494d113397f67a7f6bfccebb2595504f0
Modbus plugin: reformat code, and add comment.
1 files changed, 36 insertions(+), 49 deletions(-)
  • +36 -49
    modbus/mb_runtime.c
    • --- a/modbus/mb_runtime.c Thu Aug 13 18:42:02 2020 +0100
    +++ b/modbus/mb_runtime.c Thu Aug 13 19:00:38 2020 +0100
    @@ -436,46 +436,6 @@
    -/* Function to activate a client node's thread */
    -/* returns -1 if it could not send the signal */
    -static int __signal_client_thread(int client_node_id) {
    - /* We TRY to signal the client thread.
    - * We do this because this function can be called at the end of the PLC scan cycle
    - * and we don't want it to block at that time.
    - */
    - if (pthread_mutex_trylock(&(client_nodes[client_node_id].mutex)) != 0)
    - return -1;
    - client_nodes[client_node_id].execute_req = 1; // tell the thread to execute
    - pthread_cond_signal (&(client_nodes[client_node_id].condv));
    - pthread_mutex_unlock(&(client_nodes[client_node_id].mutex));
    - return 0;
    -}
    -
    -
    -
    -/* Function that will be called whenever a client node's periodic timer expires. */
    -/* The client node's thread will be waiting on a condition variable, so this function simply signals that
    - * condition variable.
    - *
    - * The same callback function is called by the timers of all client nodes. The id of the client node
    - * in question will be passed as a parameter to the call back function.
    - */
    -void __client_node_timer_callback_function(int client_node_id) {
    - /* signal the client node's condition variable on which the client node's thread should be waiting... */
    - /* Since the communication cycle is run with the mutex locked, we use trylock() instead of lock() */
    - if (pthread_mutex_trylock (&(client_nodes[client_node_id].mutex)) != 0)
    - /* we never get to signal the thread for activation. But that is OK.
    - * If it still in the communication cycle (during which the mutex is kept locked)
    - * then that means that the communication cycle is falling behing in the periodic
    - * communication cycle, and we therefore need to skip a period.
    - */
    - return;
    - client_nodes[client_node_id].execute_req = 1; // tell the thread to execute
    - client_nodes[client_node_id].periodic_act = 1; // tell the thread the activation was done by periodic timer
    - pthread_cond_signal (&(client_nodes[client_node_id].condv));
    - pthread_mutex_unlock(&(client_nodes[client_node_id].mutex));
    -}
    -
    /* Thread that simply implements a periodic 'timer',
    @@ -528,10 +488,24 @@
    }
    while (0 != clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &next_cycle, NULL));
    - __client_node_timer_callback_function(client_node_id);
    +
    + /* signal the client node's condition variable on which the client node's thread should be waiting... */
    + /* Since the communication cycle is run with the mutex locked, we use trylock() instead of lock() */
    + if (pthread_mutex_trylock (&(client_nodes[client_node_id].mutex)) == 0) {
    + client_nodes[client_node_id].execute_req = 1; // tell the thread to execute
    + client_nodes[client_node_id].periodic_act = 1; // tell the thread the activation was done by periodic timer
    + pthread_cond_signal (&(client_nodes[client_node_id].condv));
    + pthread_mutex_unlock(&(client_nodes[client_node_id].mutex));
    + } else {
    + /* We never get to signal the thread for activation. But that is OK.
    + * If it still in the communication cycle (during which the mutex is kept locked)
    + * then that means that the communication cycle is falling behing in the periodic
    + * communication cycle, and we therefore need to skip a period.
    + */
    + }
    }
    - return NULL;
    + return NULL; // humour the compiler -> will never be executed!
    }
    @@ -743,13 +717,26 @@
    */
    if ((client_requests[index].flag_exec_req != 0) && (0 == client_requests[index].flag_exec_started)) {
    int client_node_id = client_requests[index].client_node_id;
    - if (__signal_client_thread(client_node_id) >= 0) {
    - /* - upon success, set flag_exec_started
    - * - both flags (flag_exec_req and flag_exec_started) will be reset
    - * once the transaction has completed.
    - */
    - client_requests[index].flag_exec_started = 1;
    - }
    +
    + /* We TRY to signal the client thread.
    + * We do this because this function can be called at the end of the PLC scan cycle
    + * and we don't want it to block at that time.
    + */
    + if (pthread_mutex_trylock(&(client_nodes[client_node_id].mutex)) == 0) {
    + client_nodes[client_node_id].execute_req = 1; // tell the thread to execute
    + pthread_cond_signal (&(client_nodes[client_node_id].condv));
    + pthread_mutex_unlock(&(client_nodes[client_node_id].mutex));
    + /* - upon success, set flag_exec_started
    + * - both flags (flag_exec_req and flag_exec_started) will be reset
    + * once the transaction has completed.
    + */
    + client_requests[index].flag_exec_started = 1;
    + } else {
    + /* The mutex is locked => the client thread is currently executing MB transactions.
    + * We will try to activate it in the next PLC cycle...
    + * For now, do nothing.
    + */
    + }
    }
    }
    }