due only 8 hours

#include <stdio.h> #include <stdlib.h> #include <stdint.h> #include <time.h> #include <pthread.h> static pthread_mutex_t mutex; static pthread_cond_t teller_available; typedef struct teller_info_t { int id; int checked_in; int doing_service; pthread_cond_t done; pthread_t thread; struct teller_info_t *next; //struct teller_info_t *prev; } *p_teller; static p_teller teller_list = NULL; void teller_check_in(p_teller teller) { teller->checked_in = 1; teller->doing_service = 0; // add teller to list if(teller->next == NULL) { // first teller ever, add it and set all global vars teller->next = teller; } else { teller->next = teller; } } void teller_check_out(p_teller teller) { // check if the teller is done // if not, wait for teller to be done // remove teller from list teller->checked_in = 0; } p_teller do_banking(int customer_id) { // check if list contains a teller (=teller is available) // if not, wait for teller to become available printf("Customer %d is served by teller %d\n", customer_id, teller->id); teller->doing_service = 1; return teller; } void finish_banking(int customer_id, p_teller teller) { printf("Customer %d is done with teller %d\n", customer_id, teller->id); teller->doing_service = 0; // re-enter teller into list } void* teller(void *arg) { p_teller me = (p_teller) arg; // perform an initial checkin teller_check_in(me); while(1) { // in 5% of the cases toggle status int r = rand(); if (r < (0.05 * RAND_MAX)) { if (me->checked_in) { printf("teller %d checks out\n", me->id); teller_check_out(me); // uncomment line below to let program terminate for testing // return 0; } else { printf("teller %d checks in\n", me->id); teller_check_in(me); } } } } void* customer(void *arg) { int id = (uintptr_t) arg; while (1) { // in 10% of the cases enter bank and do business int r = rand(); if (r < (0.1 * RAND_MAX)) { p_teller teller = do_banking(id); // sleep up to 3 seconds sleep(r % 4); finish_banking(id, teller); } } } #define NUM_TELLERS 3 #define NUM_CUSTOMERS 5 int main(void) { srand(time(NULL)); struct teller_info_t tellers[NUM_TELLERS]; int i; // initialize mutexes/condition variables for (i=0; i<NUM_TELLERS; i++) { tellers[i].id = i; tellers[i].next = NULL; pthread_create(&tellers[i].thread, NULL, teller, (void*) &tellers[i]); } pthread_t thread; for (i=0; i<NUM_CUSTOMERS; i++) { pthread_create(&thread, NULL, customer, (void*) (uintptr_t) i); } for (i=0; i<NUM_TELLERS; i++) { pthread_join(tellers[i].thread, NULL); } return 0; }