Pthread Synchronization w/o Mutex

Today, when I was just going through some Pthreads concepts. Pthreads are very useful for writing multi-threaded application, it has more advantages over multi-tasking.

Here is my program of Pthread Synchronization without using Mutex

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

int mx=0;

void *thread_function1(void *arg) {
  int i;

  for ( i=0; i<10; i++) {
    while(mx==2);
    mx=1;
    printf("Thread says hi-%d!\n",i);
    mx=2;
  }
  pthread_exit(0);
}


void *thread_function2(void *arg) {
  int i;

  for ( i=0; i<10; i++) {
    while(mx==1);
    mx=2;
    printf("Thread says hello-%d!\n",i);
    mx=1;
  }
  pthread_exit(0);
}

int main() {

  pthread_t mythread1, mythread2;
  pthread_attr_t my_attr;
  char *str;
 
  if(pthread_create( &mythread1, NULL, thread_function1, NULL) ) {
    printf("error creating thread1.");
    abort();
  }
  if(pthread_create( &mythread2, NULL, thread_function2, NULL) ) {
    printf("error creating thread2.");
    abort();
  }

  mx=1;

  if ( pthread_join (mythread1, NULL) ) {
    perror("error joining thread.");
    abort();
  }
  if ( pthread_join (mythread2, NULL) ) {
    perror("error joining thread.");
    abort();
  }
  printf("Pthread Joing Success\n");

  exit(0);

}

The main disadvantage of this code, is polling, the while() statement in the 2 threads. When you use Mutex/semaphore, this polling which consume CPU time, can be avoided. I don't know the implementation of Pthread Mutex. But we can try to analyze through time command in the next session.

Next Meet Pannalam....