Going further – mutexes and joins

We touched upon mutexes and what they are; now we are going to implement a C program that demonstrates how they work.

Create a new file called third_c_prog.c inside the c_programs directory.

vim third_c_prog.c

Add the following code to this file:

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


pthread_mutex_t mutex1 = PTHREAD_MUTEX_INITIALIZER;
pthread_t thread_id[4];
int counter = 0;

void *thread_processor()
{
 pthread_mutex_lock( &mutex1 );
 counter++;
 printf(" Counter: %d\n",counter);
 pthread_mutex_unlock( &mutex1 );
}

int main(void)
{

int i = 0;
int error;

  while(i < 4) {

  error = pthread_create(&(thread_id[i]), NULL, &thread_processor, NULL);
  if (error != 0)
  {
      printf("\nthere was a problem creating thread: %s", strerror(error));
  }
  else
  {
      printf("\n Thread number %d created.\n", i);
  }
  pthread_join( thread_id[i], NULL);
  i++;
 }

}

This program is a variation on the first...