Question

Answer this question

Properly

Please find out how many processes and how many threads are created:

                             pid_t pid;

            pid = fork();

            if (pid == 0) { /* child process */

                  fork();

                  thread_create(...);

}

fork();

a) Write working codes from the pseudo-code above. Add appropriate codes to ensure that you have time to observe processes and threads using ‘top’ and ‘H’ keystroke.

b) Draw a simple diagram showing the processes and threads in their parent/child relationship.

c) Take snapshots of your code’s execution and your observation of the processes/threads.

d) Explain why your code created this number of processes and threads

Answer 1

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <pthread.h>
#include <stdlib.h>

void *work(void * parm) {
printf("Thread Work function\n");
}

int main ()
{
pid_t child_pid1, child_pid2;
pthread_t cThread;
  
printf ("the main program process ID is %d\n", (int) getpid());
  
child_pid1 = fork () ;
// AT this point 2 processes are present
if (child_pid1 == 0) {
printf ("this is the child process1, with id %d\n", (int) getpid ());
  
int *param = (int *)malloc(2 * sizeof(int));
param[0] = 123;
param[1] = 456;
  
// Only 1 process can reach the below code
child_pid2 = fork () ;
// at this time, Again 2 process will appear
  
// So now 2 processes, each will create a new thread..
pthread_create(&cThread, NULL, work, param);

  
if (child_pid2 > 0)
{
printf ("this is child process1 after forking its child\n");
}
else if (child_pid2 == 0) {
printf ("this is the child process2, with id %d\n", (int) getpid ());
}
}
  
// 4 processes will reach here..
fork();
// Total 8 processes will reach at this stage
  

return 0;
}

/// Comments inline.. I do not have a linux system to run the program and check the output.. because system calls like fork will not work on windows system.