I have this specification:
task 0 sends integer numbers (starting from 1) to task 1. Task 1 shall multiply the numbers with -1 and send them back to task 0. Task 0 shall then print these numbers to the console. For the communication between task 0 and task 1 a single memory location sharedAddress shall be used, i.e. both task 0 and task 1 read and write to/from this location! Save the file as SharedMemory.c. The execution of the program shall give the following output. Sending : 1 Receiving : -1 Sending : 2 Receiving : -2 ...
I wrote this program but the tasks are not synchronizing correctly, I think I might've done something wrong with the semaphores or the context switch.
I get this output instead where the number sometimes counts down because the tasks didn't synchonize correctly:
Receiving 17
Sending : 16
Receiving -16
Sending : -17
Receiving 17
Sending : 16
Receiving -16
Sending : -17
Receiving 17
Sending : 16
Receiving -16
Sending : -17
Receiving 17
Sending : 16
Receiving -16
Sending : -17
Receiving 17
Sending : 16
Receiving -16
Sending : -17
Receiving 17
Sending : 16
Receiving -16
Sending : -17
Receiving 17
Sending : 16
Receiving -16
Sending : -17
Receiving 17
Sending : 16
Receiving -16
Sending : -17
Receiving 17
Sending : 16
Receiving -16
Sending : -17
Receiving 17
Sending : 16
Receiving -16
Sending : -17
Receiving 17
Sending : 16
Receiving -16
Sending : -17
Receiving 17
Sending : 16
Receiving -16
Sending : -17
Receiving 17
The program that I need to change is
#include <stdio.h>
#include "includes.h"
#include <string.h>
#define DEBUG 0
/* Definition of Task Stacks */
/* Stack grows from HIGH to LOW memory */
#define TASK_STACKSIZE 2048
OS_STK task1_stk[TASK_STACKSIZE];
OS_STK task2_stk[TASK_STACKSIZE];
OS_STK stat_stk[TASK_STACKSIZE];
OS_EVENT *aSemaphore;
/* Definition of Task Priorities */
#define TASK1_PRIORITY 6 // highest priority
#define TASK2_PRIORITY 7
#define TASK_STAT_PRIORITY 12 // lowest priority
int number = 1;
void handle_button_interrupts(void* context, alt_u32 id)
{
volatile int* edge_capture_ptr = (volatile int*) context;
OSIntEnter();
// Read the edge capture register on the button PIO
//*edge_capture_ptr =
//IORD_ALTERA_AVALON_PIO_EDGE_CAP(BUTTON_PIO_BASE);
OSIntExit();
}
void printStackSize(INT8U prio)
{
INT8U err;
OS_STK_DATA stk_data;
err = OSTaskStkChk(prio, &stk_data);
if (err == OS_NO_ERR)
{
if (DEBUG == 1)
printf("Task Priority %d - Used: %d; Free: %d\n",
prio, stk_data.OSFree, stk_data.OSUsed);
}
else
{
if (DEBUG == 1)
printf("Stack Check Error!\n");
}
}
/* Producer */
void task1(void* pdata)
{
INT8U err;
while (1)
{
char text1[] = "Sending : ";
char text2[] = "Receiving : ";
int i;
OSSemPend(aSemaphore, 0, &err); // Trying to access the key
for (i = 0; i < strlen(text1); i++)
putchar(text1[i]);
printf("%d", number);
putchar('\n');
OSSemPost(aSemaphore); // Releasing the key
OSTimeDlyHMSM(0, 0, 0, 11); // Context Switch to next task
// Task will go to the ready state
// after the specified delay
OSSemPend(aSemaphore, 0, &err); // Trying to access the key
for (i = 0; i < strlen(text1); i++)
putchar(text2[i]);
printf("%d", number);
putchar('\n');
number=-number;
number++;
OSSemPost(aSemaphore); // Releasing the key
OSTimeDlyHMSM(0, 0, 0, 11); // Context Switch to next task
// Task will go to the ready state
// after the specified delay
}
}
/* Consumer */
void task2(void* pdata)
{
INT8U err;
while (1)
{
OSSemPend(aSemaphore, 0, &err); // Trying to access the key
number = -number;
OSSemPost(aSemaphore); // Releasing the key
OSTimeDlyHMSM(0, 0, 0, 4);
}
}
/* Printing Statistics */
void statisticTask(void* pdata)
{
while(1)
{
printStackSize(TASK1_PRIORITY);
printStackSize(TASK2_PRIORITY);
printStackSize(TASK_STAT_PRIORITY);
}
}
/* The main function creates two task and starts multi-tasking */
int main(void)
{
printf("Lab 3 - Handshake\n");
aSemaphore = OSSemCreate(1); // binary semaphore (1 key)
OSTaskCreateExt
(task1, // Pointer to task code
NULL, // Pointer to argument that is
// passed to task
&task1_stk[TASK_STACKSIZE-1], // Pointer to top of task stack
TASK1_PRIORITY, // Desired Task priority
TASK1_PRIORITY, // Task ID
&task1_stk[0], // Pointer to bottom of task stack
TASK_STACKSIZE, // Stacksize
NULL, // Pointer to user supplied memory
// (not needed here)
OS_TASK_OPT_STK_CHK | // Stack Checking enabled
OS_TASK_OPT_STK_CLR // Stack Cleared
);
OSTaskCreateExt
(task2, // Pointer to task code
NULL, // Pointer to argument that is
// passed to task
&task2_stk[TASK_STACKSIZE-1], // Pointer to top of task stack
TASK2_PRIORITY, // Desired Task priority
TASK2_PRIORITY, // Task ID
&task2_stk[0], // Pointer to bottom of task stack
TASK_STACKSIZE, // Stacksize
NULL, // Pointer to user supplied memory
// (not needed here)
OS_TASK_OPT_STK_CHK | // Stack Checking enabled
OS_TASK_OPT_STK_CLR // Stack Cleared
);
if (DEBUG == 1)
{
OSTaskCreateExt
(statisticTask, // Pointer to task code
NULL, // Pointer to argument that is
// passed to task
&stat_stk[TASK_STACKSIZE-1], // Pointer to top of task stack
TASK_STAT_PRIORITY, // Desired Task priority
TASK_STAT_PRIORITY, // Task ID
&stat_stk[0], // Pointer to bottom of task stack
TASK_STACKSIZE, // Stacksize
NULL, // Pointer to user supplied memory
// (not needed here)
OS_TASK_OPT_STK_CHK | // Stack Checking enabled
OS_TASK_OPT_STK_CLR // Stack Cleared
);
}
OSStart();
return 0;
}
Can you help me?
Come to think of it again: you will probably need two semaphores:
You initialize sem1 with 0, sem2 with 1.