Question

Answer the following questions based on the given c file:

#include

#include

#include   

int c = 0;

void *fnC()

{     int i;

    for(i=0;i<10;i++)

    {   c++;

        printf(" %d", c);

    }      

}

int main()

{

int rt1, rt2;   pthread_t t1, t2; int trial_count = 0;

// For every trial, lets zero out the counter and run the count routine “twice”    

// as threads that can be scheduled onto independent cores instead of running    

// in sequence.

for (trial_count = 0; trial_count < 1000; trial_count++)

{

c = 0;

           // Create two thread with the routine pthread_create(). You can use

           // reference materials to get definitions of what the various parameters            

// mean.

            if((rt1=pthread_create( &t1, NULL, &fnC, NULL)))              

printf("Thread creation failed: %d\n", rt1);

           if((rt2=pthread_create( &t2, NULL, &fnC, NULL)))              

printf("Thread creation failed: %d\n", rt2);

          // Wait for both threads to finish. The main process thread will block

          // until the threads that were launched terminate. Once they both finish,          

// then the “main thread” unblocks and continues.

          pthread_join(t1, NULL);           

pthread_join(t2, NULL);          

printf("\n");

        }

    return 0;

}

Activity A, Task 1: Discussion Questions (10/50 points):

1. You should have observed output lines that were NOT always printed in integer order. This is because the code as written has a critical section that is being simultaneously run by more than one thread. What lines of the sample code constitute the critical section? You can cut and paste those lines into your answer, or you can type them in.  

2. Thread safety (https://en.wikipedia.org/wiki/Thread_safety) is a concept often used when discussing subroutines or other code segments that are written in such way that they can be “multiply run” as parts of multiple threads that are being scheduled concurrently or otherwise multiprogrammed. Do you think that the function _printf() is thread safe? Do some research and/or run some code experiments and provide a brief, but complete, answer that explains your view on the subject. Be sure to explain why you hold your position on the subject, no matter what that is.

Answer 1

Working code implemented in C and appropriate comments provided for better understanding.

Here I am attaching code for all files:

Source Code:

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>

int c = 0;

pthread_mutex_t lock;

void *fnC()
{
int i;
for(i=0;i<10;i++)
{ //pthread_mutex_lock(&lock);
c++;
printf(" %d", c);
//pthread_mutex_unlock(&lock);
}   

}

int main()
{
int rt1, rt2;
pthread_t t1, t2;
int trial_count = 0;

pthread_mutex_init(&lock, NULL);
  
for (trial_count = 0; trial_count < 1000; trial_count++)
{
c = 0;
/* Create two threads */
if( (rt1=pthread_create( &t1, NULL, &fnC, NULL)) )
printf("Thread creation failed: %d\n", rt1);
if( (rt2=pthread_create( &t2, NULL, &fnC, NULL)) )
printf("Thread creation failed: %d\n", rt2);
/* Wait for both threads to finish */
pthread_join( t1, NULL);
pthread_join( t2, NULL);
printf ("\n");
}

return 0;

}

Sample Output Screenshots: