Circuits Of Imagination

Pthread, Mutex and Mac OS X

08 Sep 2007

A while back I was reading Beginning Linux Programming. I never worked that much with the examples. Partially because I really never had time. So the other day I had some free time and I wanted to see what would and wouldn’t work with my Mac. So I open up the part on threading and I re-read the mutex part. A couple of man’s later and I found out that Macs supports pthread. I wrote up this little example for mutexes.

#include <stdio.h>
#include <stdlib.h>
//#include <unistd.h>
#include <pthread.h>
#include <string.h>

void *worker_function(void* arg) ;
pthread_mutex_t work_mutex ; //our little flag

int main(int argc, char* argv[]){
  int res;
  pthread_t worker_thread ;
  void* thread_result ;
  res = pthread_mutex_init(&work_mutex, NULL) ;
  if(res != 0){
    perror("Mutex Initialization Failed") ;
    exit(EXIT_FAILURE) ;
  }

  res = pthread_create(&worker_thread, NULL, worker_function, NULL) ;
  if(res != 0){
    perror("Thread creation Failed");
    exit(EXIT_FAILURE) ;
  }
  int i ;
  for(i = 0; i<10; i++){
    pthread_mutex_lock(&work_mutex) ;
    printf("Main Thread: %d\n", i) ;
    pthread_mutex_unlock(&work_mutex) ;
  }
  
  printf("Waiting for worker thread to finish\n") ;
  res = pthread_join(worker_thread, &thread_result) ;
  if(res != 0){
    perror("Worker thread crashed") ;
    exit(EXIT_FAILURE) ;
  }
  pthread_mutex_destroy(&work_mutex) ;
  exit(EXIT_SUCCESS) ;
}

void* worker_function(void* arg) {
  int i ;
  for(i = 0; i < 20 ; i++){
    pthread_mutex_lock(&work_mutex) ;
    printf("Worker thread: %d\n", i) ;
    pthread_mutex_unlock(&work_mutex) ;
  }
  pthread_exit(0) ;
}

Nothing much… kinda like the “Hello, world” of threading but I like. Hopefully I’ll have the chance to work wiht queues soon

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