线程项目问题|如何从C中的多个线程等待/信号

Question

我实际上是在做一个个人项目，我必须制作一个模拟这种行为的小程序：

有两种类型的人：村民和德鲁伊（作为Asterix/obelix）

每个村民都由ID确定（这是一个独特的数字村民）。它将在离开之前与“ nb_fights”时间打架 战场。每次战斗之前 它必须告知德鲁伊，然后等到锅重新填充锅。

德鲁伊将等待一个村民召唤。然后，它将用锅尺寸的食物重新填充锅。当NB_Refills 已经完成了，德鲁伊的成分已经用光了，它的线程必须停止。

所有内容都以参数（./ panoramix＆lt; nb_villagers＆gt;＆lt; lt; pot_size＆gt; nb_fights＆gt; nb_refills＆gt; nb_refills＆gt; gt; gt; gt; gt; gt; gt;

实际上，我实际上是我做了70％的项目，但是我做了70％的人，但我却遇到了麻烦的是druiid druil druil the potions potions。

有村民线程的代码：

void *villager(void *args)
{
    int pNb = nbF;
    int id = *(int *)args;
    
    printf("Villager %d: Going into battle!\n", id);
    while (pNb > 0) {
        pthread_mutex_lock(&mpot);
        printf("Villager %d: I need a drink... I see %d servings left.\n", id, pot_size);
        if (pot_size == 0) {
            printf("Villager %d: Hey Pano wake up! We need more potion.\n", id);
            sem_wait(&test);
        }
        pot_size--;
        pthread_mutex_unlock(&mpot);
        pNb--;
        printf("Villager %d: Take that roman scum! Only %d left.\n", id, pNb);
    }
    printf("Villager %d: I’m going to sleep now.\n", id);
}

使用 pnb =战斗数（我们减少），

然后有德鲁伊线程：

void *druid(void *args)
{
    int sizepot = pot_size;

    printf("Druid: I'm ready... but sleepy...\n");
    while (nb_refills > 0) {
        while (pot_size != 0) {
        }
        sem_wait(&test);
        nb_refills--;
        printf("Druid: Ah! Yes, yes, I'm awake! Working on it! Beware I can only make %d more refills after this one.\n", nb_refills);
        pot_size = sizepot;
        sem_post(&test);
    }
    printf("Druid: I'm out of viscum. I'm going back to... zZz\n");
}

我想知道我如何“调用” druid当“ pot_size”为空（= 0）。

我试图在if条件下使用信号量进行操作：（

        if (pot_size == 0) {
            printf("Villager %d: Hey Pano wake up! We need more potion.\n", id);
            sem_wait(&test);
        }

等待填充pot_size然后继续程序的druid），但我认为这不是很好。

编辑：整个代码：

#include "struct.h"

sem_t test;
pthread_mutex_t mpot;
pthread_mutex_t fill;
int nbV = 0;
int pot_size = 0;
int nbF = 0;
int nb_refills = 0;

int errorhandler(int ac, char **av)
{
    if (ac != 5)
    {
        printf("USAGE: ./panoramix <nb_villagers> <pot_size> <nb_fights> <nb_refills> \nValues must be > 0.\n");
        return (84);
    }
    if (atoi(av[1]) == 0 || atoi(av[2]) == 0 || atoi(av[3]) == 0 || atoi(av[4]) == 0)
    {
        printf("USAGE: ./panoramix <nb_villagers> <pot_size> <nb_fights> <nb_refills> \nValues must be > 0.\n");
        return (84);
    }
    return (0);
}

void *druid(void *args)
{
    int sizepot = pot_size;

    printf("Druid: I'm ready... but sleepy...\n");
    while (nb_refills > 0) {
        while (pot_size != 0) {
            usleep(1000);
        }
        pthread_mutex_lock(&fill);
        nb_refills--;
        printf("Druid: Ah! Yes, yes, I'm awake! Working on it! Beware I can only make %d more refills after this one.\n", nb_refills);
        pot_size = sizepot;
        pthread_mutex_unlock(&fill);
    }
    printf("Druid: I'm out of viscum. I'm going back to... zZz\n");
}

void *villager(void *args)
{
    int pNb = nbF;
    int id = *(int *)args;
    
    printf("Villager %d: Going into battle!\n", id);
    while (pNb > 0) {
        pthread_mutex_lock(&mpot);
        printf("Villager %d: I need a drink... I see %d servings left.\n", id, pot_size);
        if (pot_size == 0) {
            printf("Villager %d: Hey Pano wake up! We need more potion.\n", id);
        }
        pot_size--;
        pthread_mutex_unlock(&mpot);
        pNb--;
        printf("Villager %d: Take that roman scum! Only %d left.\n", id, pNb);
    }
    printf("Villager %d: I’m going to sleep now.\n", id);
}

int main(int ac, char **av)
{
    if (errorhandler(ac, av) == 84)
        return (84);
    nbV = atoi(av[1]);
    pot_size = atoi(av[2]);
    nbF = atoi(av[3]);
    nb_refills = atoi(av[4]);
    pthread_t th[nbV];
    int i;

    pthread_mutex_init(&mpot, NULL);
    pthread_mutex_init(&fill, NULL);
    sem_init(&test, 0, 1);
    for (int i = 0; i < nbV; i++) {
        int *a = malloc(sizeof(int));
        *a = i;
        if (pthread_create(&th[i], NULL, &villager, a) != 0) {
            perror("Failed to create the Villager\n");
        }
    }
    pthread_create(&th[nbV], NULL, &druid, NULL);
    for (int i = 0; i < atoi(av[1]); i++) {
        if (pthread_join(th[i], NULL) != 0) {
            perror("Failed to launch the Villager\n");
        }
    }
    sem_destroy(&test);
    pthread_mutex_destroy(&mpot);
    pthread_mutex_destroy(&fill);
    return (0);
}

Answer 1

1. 将游戏所需的所有全局变量分组到 struct 中，在一个位置访问它们变得更容易。

typedef struct {
    int nbV;            // # of villagers
    int nbF;            // # of fights each villager takes on
    int nb_refills;     // # of potion refills that druid can make
    int pot_size;       // size of potion pot
    int potion_left;    // remaining potion in pot for consumption
    int druid_awake;    // flag only modified by druid
    int villagers_awake;
    sem_t pot_sem;
    pthread_mutex_t potion_mutex;
} sPanoramix_t;

sPanoramix_t pgame;

1. druid（）不应调用 sem_wait（），因为这是生产者。如果所有的村民都在战斗中完成，请检查所有村庄是否在睡觉，请返回/退出。

void *druid (void *args) {
    printf ("Druid: I'm ready... but sleepy...\n");
    pgame.druid_awake = 1;
    while (pgame.nb_refills > 0) {
        while (pgame.potion_left > 0) {
            if (!pgame.villagers_awake) {
                printf ("Druid: KILLED all of them today! Drinks are on me :-)\n");
                return NULL;
            }
            usleep (1000);
        }
        pgame.nb_refills--;
        printf ("Druid: Ah! Yes, yes, I'm awake! Working on it! Beware I can only make %d more refills after this one.\n", pgame.nb_refills);
        pgame.potion_left = pgame.pot_size;
        printf ("Druid: Kill those romans, potion refilled to %d\n", pgame.potion_left);
        sem_post (&pgame.pot_sem);
    }
    printf ("Druid: ALERT!! I'm out of viscum. I'm going back to... zZz\n");
    pgame.druid_awake = 0;    // druid is not available anymore
    return NULL;
}

3. 村民需要检查德鲁伊是否入睡，即。用尽了所有补充点。从那以后，只有一个线程具有静音＆amp;没有药水可以消耗，我们可以在 sem_wait（）上阻止Druid重新填充＆am​​p; sem_post（）。

void *villager (void *args) {
    int pNb = pgame.nbF;
    int id = (unsigned long)args;

    printf ("Villager %d: Going into battle!\n", id);
    while (pNb > 0) {
        pthread_mutex_lock (&pgame.potion_mutex);
        printf ("Villager %d: I need a drink... I see %d servings left.\n", id, pgame.potion_left);
        if (pgame.potion_left <= 0) {
            if (!pgame.druid_awake) {
                printf ("Villager %d: We're doomed now Pano!\n", id);
                pthread_mutex_unlock (&pgame.potion_mutex);
                return NULL;
            }
            printf ("Villager %d: Hey Pano wake up! We need more potion.\n", id);
            sem_wait (&pgame.pot_sem);
            printf ("Villager %d: Thank you PANO!\n", id);
        }
        pgame.potion_left--;
        pthread_mutex_unlock (&pgame.potion_mutex);
        pNb--;
        printf ("Villager %d: Take that Roman scum! Only %d left.\n", id, pNb);
        usleep (1000); // let other villagers take turn
    }
    printf ("Villager %d: KILLED my quota of Romans, I’m going to sleep now.\n", id);
    pthread_mutex_lock (&pgame.potion_mutex);
    pgame.villagers_awake --;
    pthread_mutex_unlock (&pgame.potion_mutex);

    return NULL;
}

4. 修改后的 main（）：

int main (int ac, char **av) {
    if (errorhandler (ac, av) == 84)
        return (84);

    pgame.nbV = atoi (av[1]);
    pgame.villagers_awake = pgame.nbV;
    pgame.pot_size = atoi (av[2]);
    pgame.potion_left = pgame.pot_size;
    pgame.nbF = atoi (av[3]);
    pgame.nb_refills = atoi (av[4]);
    pthread_t th[pgame.nbV + 1];

    pthread_mutex_init (&pgame.potion_mutex, NULL);
    sem_init (&pgame.pot_sem, 0, 1);
    pthread_create (&th[0], NULL, druid, NULL);
    usleep (1000);
    for (int i = 1; i <= pgame.nbV; i++) {
        if (pthread_create (&th[i], NULL, villager, (void*) (unsigned long)i) != 0)
            perror ("Failed to create the Villager\n");
    }
    for (int i = 0; i <= pgame.nbV; i++) {
        if (pthread_join (th[i], NULL) != 0)
            perror ("Failed pthread_join()\n");
    }
    sem_destroy (&pgame.pot_sem);
    pthread_mutex_destroy (&pgame.potion_mutex);

    printf ("End of game Panoramix!\n");
    return (0);
}

5. 使用 strtol（）而不是 atoi（），它为您提供了更多的控制：如何将字符串转换为c？

   中的整数

6. 中的整数，如果线程没有将任何有意义的线程返回使用 pthread_join（ ）。