Semaphores

[CaptRage61]

I am working on using semaphores to keep two threads from writing to the same variable but this is now working correctly, I beleive that the semaphore is created correctly can anyone tell if this is right:

int p(){
//sem is the sembuf struct
//x is the semid
  sem.sem_op = -1;
  semop(x, &sem, 1);
}

int v(){
  sem.sem_op = 1;
  semop(x, &sem, 1);
}


int producer()
{
   int i,in, local, sum = 0;
   printf(" Producer: writing %d items.\n", PRODUCER_REPS);

   i = 0;
   while (i < PRODUCER_REPS)
   {
      while (counter == BUFFER_SIZE) ;


      buffer[in] = ++i;
      in = (in + 1) % BUFFER_SIZE;

      // The next 4 lines implement a "slow" counter++;
      local = counter;
      local++;
      if (i == 10) work(100000);
      counter = local;

      p(); //this will force the consumer to wait till this
           //command is executed before it can update counter
           //and the buffer

      sum += i;
   }
   printf(" Producer done! Checksum was %d\n", sum);
}

int consumer()
{
   int i;
   int out;
   int sum = 0;
   printf("     Consumer: reading items.\n");

   i = 0;
   out = 0;
   while (i < PRODUCER_REPS)
   {
      while (counter == 0) ;

      v(); //waits for producer to update counter before
           //it can update counter and buffer

      i = buffer[out];
      out = (out + 1) % BUFFER_SIZE;

      counter--;

      sum += i;
   }
   printf("     Consumer checksum = %d\n",sum);
}

 

[Salem]

How exactly are you calling producer and consumer?



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[CaptRage61]

p = clone(producer, p_stackTop, CLONE_VM | SIGCHLD, NULL);
c = clone(consumer, c_stackTop, CLONE_VM | SIGCHLD, NULL);

 

[Salem]

I think you need to show the whole program

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[CaptRage61]

actually I think I just got it to work, thanks though