Solution for barber problem~

sync04_barber.c

#include <unistd.h>
#include <pthread.h>
#include <semaphore.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#define N 10
#define TN 3
#define MAX_WTIME 5
#define MAX_BTIME 5

sem_t waiting;          // ==0表示当前没有顾客等待, >0表示有顾客在等待
sem_t seat;             // ==1表示理发椅就绪
sem_t finish;           // ==1表示当前被服务顾客服务完成
sem_t mutex;            // 临界区标志
sem_t lockseat;         // ==1表示最先来到的顾客已经锁定理发椅
sem_t leave;            // ==1表示当前被服务顾客已经离开理发椅
int waiting_num;        // 当前排队人数
int* table;             // 记录当前等待椅状况
int barber_table;       // 记录当前理发椅状况

void* customer(void* cid);
void* barber(void* bid);

int main(int argc, char** argv) {
    srand(0);
    waiting_num = 0;
    table = (int*)(malloc(sizeof(int) * TN));
    memset(table, 0, sizeof(int) * TN);
    barber_table = 0;
    sem_init(&waiting, 0, 0);
    sem_init(&seat, 0, 0);
    sem_init(&finish, 0, 0);
    sem_init(&mutex, 0, 1);
    sem_init(&lockseat, 0, 0);
    sem_init(&leave, 0, 0);
    pthread_t barber_thread;
    pthread_t* customer_threads = (pthread_t*)(malloc(sizeof(pthread_t) * N));
    pthread_create(&barber_thread, NULL, barber, NULL);
    int i = 0;
    for (; i < N; ++i) {
        sleep(rand() % MAX_WTIME);
        pthread_create(&customer_threads[i], NULL, customer, (void*)(i + 1));
    }
    void* threadres = NULL;
    for (i = 0; i < N; ++i) {
        pthread_join(customer_threads[i], &threadres);
    }
    free(table);
    free(customer_threads);
    sem_destroy(&waiting);
    sem_destroy(&seat);
    sem_destroy(&finish);
    sem_destroy(&mutex);
    sem_destroy(&lockseat);
    return 0;
}

void* customer(void* cid) {
    int id = (int)cid;
    int seatnum = 0;
    sem_wait(&mutex);
    {
        int t = 0;
        printf("%d customer entered, and %d customers are waiting...\n", id, waiting_num);
        if (waiting_num == TN) {
            printf("No available seat! Exit now!\n");
            sem_post(&mutex);
            pthread_exit(NULL);
        }
        for (t = 0; t < TN; ++t) {
            if (table[t] == 0) {
                seatnum = t;
                table[seatnum] = id;
                break;
            }
        }
        printf("%d customer sits at %d!\n", id, seatnum);
        for (t = 0; t < TN; ++t)
            printf("SEAT%d\t", t);
        printf("BARBERSEAT\n");
        for (t = 0; t < TN; ++t)
            printf("%d\t", table[t]);
        printf("%d\n", barber_table);
        ++waiting_num;
    }
    sem_post(&mutex);
    sem_post(&waiting);
    sem_wait(&seat);
    sem_wait(&mutex);
    {
        table[seatnum] = 0;
        barber_table = id;
        --waiting_num;
    }
    sem_post(&mutex);
    sem_post(&lockseat);
    sem_wait(&finish);
    sem_wait(&mutex);
    {
        printf("Customer %d has just had his hair cut!\n", id);
        barber_table = 0;
    }
    sem_post(&mutex);
    sem_post(&leave);
    pthread_exit(NULL);
}

void* barber(void* bid) {
    while (1) {
        if (waiting_num == 0)
            printf("Barber is sleeping...\n");
        sem_wait(&waiting);
        printf("Barber starts working...\n");
        sem_post(&seat);
        sem_wait(&lockseat);
        sleep(rand() % MAX_BTIME);
        sem_post(&finish);
        sem_wait(&leave);
    }
}