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这是字符函数的一部分，它将 256 到 1024 字节范围内的数据发送到缓冲区

    semaphore_p(semMutexAll);//critical section
    int charByte =rand() % 768 + 256;
    for(i=0 ; i<charByte ; i++)
         semaphore_p(semBuff);//contor buffer overflow
    semaphore_v(semMutexAll);

这是函数 cpu 的一部分，它在 10 毫秒内从缓冲区读取 2 个字节

while(1)
{
      semaphore_v(semBuff);
      semaphore_v(semBuff);
      usleep(10000);
}

这是信号量

    semBuff = semget((key_t)1234,1,0666|IPC_CREAT); //Gets shared memory Id --> 1234 key
    semChar = semget((key_t)1235,1,0666|IPC_CREAT);
    semImage  = semget((key_t)1236,1,0666|IPC_CREAT);       
    semAudio  = semget((key_t)1237,1,0666|IPC_CREAT);
    semVideo  = semget((key_t)1238,1,0666|IPC_CREAT);
    semMutexCpu  = semget((key_t)1239,1,0666|IPC_CREAT);
    semMutexAll  = semget((key_t)1230,1,0666|IPC_CREAT);

    set_semvalue(semBuff,BUFFSIZE);
    set_semvalue(semChar,MAXCHR);
    set_semvalue(semImage,MAXIMAGE);
    set_semvalue(semAudio,MAXAUDIO);
    set_semvalue(semVideo,MAXVIDEO);
    set_semvalue(semMutexCpu,1);
    set_semvalue(semMutexAll,1);

这里是共享内存

    key_t ShmKEY;
    key_t ShmQ;

    int ShmContID;
    int ShmQID;
    int status;

    queue *buffArea;
    buffArea = (queue*)malloc(sizeof(queue));
    initQueue(buffArea);
    control * params;
    params = (control*)malloc(sizeof(control));

    ShmKEY = ftok("./", 'A');
    ShmQ = ftok("./", 'B');

    if((ShmContID = shmget(ShmKEY,sizeof(params),IPC_CREAT | 0666)) == -1)
    { 
        //Gets shared memory Id --> IPC_PRIVATE key
        perror("shmget");
        exit(1);    
    }

    if((ShmQID = shmget(ShmQ,sizeof(buffArea),IPC_CREAT | 0666)) == -1)
    {
        //Gets shared memory Id --> IPC_PRIVATE key
        perror("shmget");
        exit(1);    
    }

这是信号量标头

    #ifndef SHAREDSMPH_H_
    #define SHAREDSMPH_H_

    #include <unistd.h>
    #include <stdlib.h>
    #include <stdio.h>
    #include <sys/ipc.h>
    #include <sys/types.h>
    #include <sys/sem.h>
    #include <sys/wait.h>
    #include <string.h>
    #include <errno.h>

    union semun 
    {
        int val;
        struct semid_ds *buf;
        unsigned short *array;
    };

    static int semBuff;
    static int semChar;
    static int semImage;
    static int semAudio;
    static int semVideo;
    static int semMutexCpu;
    static int semMutexAll;

    static int set_semvalue(int sem_id,int val)
    {
        union semun sem_union;
        sem_union.val=val;
        if(semctl(sem_id,0,SETVAL,sem_union) == -1)
        {
            fprintf(stderr, "Failed to semvalue\n");        
            return(0);
        }
        return (1);
    }

    static void del_semvalue(int sem_id)
    {
        union semun sem_union;
        if(semctl(sem_id,0,IPC_RMID,sem_union) == -1)
            fprintf(stderr, "Failed to delete semaphore\n");
    }

    static int get_semvalue(int sem_id)
    {
        union semun sem_union;

        int value = semctl(sem_id,0,GETVAL,sem_union);  
        //printf("semvalue:%d\n",value);
        return value;
    }

    static int semaphore_p(int sem_id)
    {
        struct sembuf sem_b;
        sem_b.sem_num=0;
        sem_b.sem_op=-1; /* P */
        sem_b.sem_flg=SEM_UNDO;

        if(semop(sem_id,&sem_b,1) == -1)
        {
            printf("semaphore_p failed\n");
            return (0); 
        }
        return (1);
    }

    static int semaphore_v(int sem_id)
    {
        struct sembuf sem_b;
        sem_b.sem_num=0;
        sem_b.sem_op=1; /* V */
        sem_b.sem_flg=SEM_UNDO;
        if(semop(sem_id,&sem_b,1) == -1)
        {
            printf("semaphore_v failed\n");
            return (0); 
        }
        return (1);
    }
    #endif

这段代码有问题吗？特别是信号量，问题是信号量值总是在不同的进程中初始化。当我在进程中调用 semaphore_v 和 semaphore_p 函数时，它们工作准确，但例如 semBuff 信号量总是初始化为 1024。

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