Member Avatar for smith32 
sem_t w,r,s1,s2,s3;
pthread_mutex_t m;


int main(int argc, char* argv[])
{
  
   mutex and semaphores initialization .....

   call threads....

   wait until finish and cancel threads...
   
   clean threads and semaphores

   [I]exit;[/I]
}



void *reader(void *argv)
{
   
   while(TRUE)
   {
      sem_wait(&r);
      sem_wait(&s1);
      pthread_mutex_lock(&m);
      
      ... read data.....

      pthread_mutex_unlock(&m);
      sem_post(&s1);
      sem_post(&w);   
   } 
   printf("Done read\n");
   sem_post(&extra2);
   pthread_exit(NULL);
}

void *writer(void *argv)
{
   
   while(TRUE)
   {
     sem_wait(&w);
     sem_wait(&s1);
     pthread_mutex_lock(&m);
     
    
     pthread_mutex_unlock(&m);
     sem_post(&s1);
     sem_post(&r);
   }
   printf("Done Write\n");
   sem_post(&s3);
   pthread_exit(NULL);
}

I wrote a reader/writer issue and now it's writing the same as from the source ... but sometime it become unstable and making output wrong or stop working.. Can someone plz show me the unstable part? if need, i'll also provide my code. Thanks in advance..

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  • 3 Months Discussion Span
  • Latest Post Latest Post by Abhineet.Ayan
Member Avatar for Abhineet.Ayan

Post the code or just a part of code. Which compiler are you using? Try to compile it step by step for 5-8 times and you will get to know, which part is guilty :-)

sem_t w,r,s1,s2,s3;
pthread_mutex_t m;


int main(int argc, char* argv[])
{
  
   mutex and semaphores initialization .....

   call threads....

   wait until finish and cancel threads...
   
   clean threads and semaphores

   [I]exit;[/I]
}



void *reader(void *argv)
{
   
   while(TRUE)
   {
      sem_wait(&r);
      sem_wait(&s1);
      pthread_mutex_lock(&m);
      
      ... read data.....

      pthread_mutex_unlock(&m);
      sem_post(&s1);
      sem_post(&w);   
   } 
   printf("Done read\n");
   sem_post(&extra2);
   pthread_exit(NULL);
}

void *writer(void *argv)
{
   
   while(TRUE)
   {
     sem_wait(&w);
     sem_wait(&s1);
     pthread_mutex_lock(&m);
     
    
     pthread_mutex_unlock(&m);
     sem_post(&s1);
     sem_post(&r);
   }
   printf("Done Write\n");
   sem_post(&s3);
   pthread_exit(NULL);
}

I wrote a reader/writer issue and now it's writing the same as from the source ... but sometime it become unstable and making output wrong or stop working.. Can someone plz show me the unstable part? if need, i'll also provide my code. Thanks in advance..

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