UC3M

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// compile with $ gcc -Wall -g *.c -pthread -o program
// run with ./program
// check with valgrind --tool=helgrind ./program
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>

pthread_mutex_t mutex;
pthread_cond_t cond;
void* thread_run(void* data_exit)
{ 
  int i_tmp=-1;

  sleep(2); 
  printf("[TH_ID:%ld]: Hello from the thread \n", pthread_self());
  printf("[TH_ID:%ld]: Reading %i \n", pthread_self(),(*(int*)data_exit));
  i_tmp=(*(int*)data_exit);
  
  pthread_mutex_lock(&mutex);
  for(;i_tmp==0;)
  {
   i_tmp=(*(int*)data_exit);
    if(i_tmp!=0)
    { 
      (*(int*)data_exit)--;
      pthread_mutex_unlock(&mutex); 
      return data_exit;
    }
    else
    { 
      printf("[TH_ID:%ld]:let's wait, data is %i  \n", pthread_self(),i_tmp);
      pthread_cond_wait(&cond,&mutex);
      //sleep(2);
      
    }
   }  
  printf("[TH_ID:%ld]: Writing %i \n", pthread_self(),(*(int*)data_exit));
  printf("[TH_ID:%ld]: To exit...............\n",pthread_self());
  return data_exit;
}


int main()
{ int i;
  pthread_t thread[2];
  int i_salir=0; //Number of threads that may exit
  int thread_rc;
  
  if(pthread_mutex_init(&mutex,NULL)!=0) 
    return -1;
  if(pthread_cond_init(&cond,NULL)!=0) 
    return -1;
  for (i=0;i<2; i++)
  { printf("[MAIN:%ld]: Starting............ \n",pthread_self());
  if ((thread_rc=pthread_create(&thread[i],NULL,thread_run,&i_salir))!=0)
  {
    printf("Error creating the thread. Code %i",thread_rc);
    return -1;
  }
  }
  
  
  sleep(1);
  printf("[MAIN:%ld]: Thread allocated \n",pthread_self());
  sleep(3);
  //Say to the thread you should exit
  pthread_mutex_lock(&mutex);
  pthread_cond_signal(&cond);
  pthread_cond_signal(&cond);
  i_salir=2;
  pthread_mutex_unlock(&mutex);
  
  
  int *ptr_output_data;
  for ( i=0;i<2; i++)
  {
    pthread_join(thread[i],(void **)&ptr_output_data);
  }
  
  pthread_mutex_destroy(&mutex);
  pthread_cond_destroy(&cond);
  printf("[MAIN:%ld]: Thread pending to return %d \n",pthread_self(), *ptr_output_data);
  return 0;
}