need immediate help about semaphore synchronization.

Osman Yagmurdereli — Sat, 24 Mar 2007 11:11:34 GMT

I can't solve the problem in this producer consumer problem for printer spooling.

void *printer(void *args) //producer
{
int holder_1,i;

while (general_counter < n)
{
sem_wait(&queues);

sem_wait(&mutex);
holder_1=dequeue(&q);
dequeue_counter++;
sem_post(&mutex);

printf("Job(%d) starts printing with %dK. (%.3f seconds left.)\n", dequeue_counter, holder_1, (float)holder_1*0.01);

for(i=0; i {
usleep(10000);
time_complete=time_complete-0.01;
sem_post(&full);
}

printf("Job(%d) completed printing.\n", dequeue_counter);

sem_wait(&mutex);
general_counter++;
sem_post(&mutex);

}

return NULL;
}

void *consumer_job(void *args) //consumer
{
int consume_value, i;

consume_value=rand()%1024 + 50;

printf("A new job arrived with %dKb.\n", consume_value);

for(i=0; i sem_wait(&full);

time_complete=time_complete + (float)(consume_value * 0.01);

sem_wait(&mutex);
enqueue(&q, consume_value);
enqueue_counter++;
printf("Job(%d) with %dKb enqued. %.3f seconds left to start.\n", enqueue_counter, consume_value, time_complete-(float)(consume_value * 0.01));
sem_post(&queues);
sem_post(&mutex);

return NULL;
}

Problem is that when the queue is empty and and the FULL semaphore value is 0, it enters to a deadlock. I can't think anything. :(

If anyone has any idea about how I can fix it, I would be appreciate...

Re: need immediate help about semaphore synchronization.

Osman Yagmurdereli — Sat, 24 Mar 2007 11:13:35 GMT

semaphore FULL is initialized to 2048. (source)
semaphore MUTEX is initialized to 1.
semaphore QUEUE is initialized to 0.

Re: need immediate help about semaphore synchronization.

Dennis Handly — Sun, 25 Mar 2007 22:35:21 GMT

Should be be doing a post of queues before the post of mutex?

You also seem to be doing a random number of wait on full, is this passed to the producer to do that number of posts?

(Any reason you are casting to float instead of double?)

topic need immediate help about semaphore synchronization. in Operating System - HP-UX

need immediate help about semaphore synchronization.

Re: need immediate help about semaphore synchronization.

Re: need immediate help about semaphore synchronization.