FreeRTOS: Critical section und blockierender Queue

  portENTER_CRITICAL();

  {

    /* Is there space to write directly to the UART? */

    if( *plTHREEmpty == ( portLONG ) pdTRUE )

    {

      /* We wrote the character directly to the UART, so was 

      successful. */

      *plTHREEmpty = pdFALSE;

      UART0_THR = cOutChar;

      xReturn = pdPASS;

    }

    else 

    {

      /* We cannot write directly to the UART, so queue the character.

      Block for a maximum of xBlockTime if there is no space in the

      queue. */

      /* was passiert wenn dieser Queue blockt? context switch? */

      xReturn = xQueueSend( xCharsForTx, &cOutChar, xBlockTime );

      /* Depending on queue sizing and task prioritisation:  While we 

      were blocked waiting to post interrupts were not disabled.  It is 

      possible that the serial ISR has emptied the Tx queue, in which

      case we need to start the Tx off again. */

      if( ( *plTHREEmpty == ( portLONG ) pdTRUE ) && ( xReturn == pdPASS )

)

      {

        xQueueReceive( xCharsForTx, &cOutChar, serNO_BLOCK );

        *plTHREEmpty = pdFALSE;

        UART0_THR = cOutChar;

      }

    }

  }

  portEXIT_CRITICAL();