信号量的使用,程序卡住了

yandong 发布于 2014/04/25 15:47
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我的代码如下,一个很简单的使用信号量的代码示例,但是这个程序经常会卡住,不知什么原因,得到的结果如下

doa@doa-pc:~$ ./a.out 
SEM1 is 1
SEM2 is 0
main is waiting
semaphore_p [0 2]is begin
semaphore_v [0]is begin
semaphore_v [0]is over
semaphore_v [0]is begin
semaphore_v [1]is over
semaphore_p [0]is over
ALL is over                 这次正常结束了
doa@doa-pc:~$ ./a.out 
SEM1 is 1
SEM2 is 0
main is waiting
semaphore_p [0 2]is begin
semaphore_v [0]is begin
semaphore_v [1]is over
semaphore_v [1]is begin
semaphore_v [2]is over  。。。卡住了结束会出现ALL is over


主体代码如下

void * fun(void)
{

        semaphore_v(sem_id_2);
        semaphore_v(sem_id_2);

}

int main()
{
    sem_id_2 = semget((key_t)4321, 1, 0666 | IPC_CREAT);
    int r;
    if((r=set_semvalue(sem_id_2,0))<0 )
    {
        fprintf(stderr, "Failed to initialize semaphore%d\n",r);
    }

    printf("SEM2 is %d\n",get_semvalue(sem_id_2));
    pthread_t consume_tid;

    pthread_create(&consume_tid, NULL, fun, NULL);

    printf("main is waiting\n");
    semaphore_p(sem_id_2,2);
    printf("ALL is over\n");
    pthread_join(consume_tid, NULL);
    return 1;
}



全部代码如下


#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <stdio.h>
#include <xenctrl.h>
#include <xen/domctl.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/select.h>
#include <signal.h>
#include <xen/event_channel.h>
#include <mysql/mysql.h>
#include <libdis.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <xs.h>
#include <pthread.h>
#include <sys/sem.h>
pthread_mutex_t thread_over_mutex=PTHREAD_MUTEX_INITIALIZER;

static int set_semvalue(int sem_id, int val);
static void del_semvalue(int sem_id);
static int semaphore_p(int sem_id, int used);
static int semaphore_v(int sem_id);
static int get_semvalue(int sem_id);
union semun
{
               int              val;    /* Value for SETVAL */
               struct semid_ds *buf;    /* Buffer for IPC_STAT, IPC_SET */
               unsigned short  *array;  /* Array for GETALL, SETALL */
               struct seminfo  *__buf;  /* Buffer for IPC_INFO
                                           (Linux-specific) */
};

static int sem_id_1;
static int sem_id_2;
struct sembuf sem_b;

static int set_semvalue(int sem_id, int val)
{
    union semun sem_union;

    sem_union.val = val;//-(THREAD_NUM-1);
    return semctl(sem_id, 0, SETVAL, sem_union);
}

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

    //sem_union.val = val;//-(THREAD_NUM-1);

    return semctl(sem_id, 0, GETVAL, sem_union);
}

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 semaphore_p(int sem_id, int used)
{

    sem_b.sem_num = 0;
    sem_b.sem_op = -1;
    sem_b.sem_flg = SEM_UNDO;
    printf("semaphore_p [%d %d]is begin\n", get_semvalue(sem_id),used);
    if(semop(sem_id, &sem_b, used) == -1)
    {
        fprintf(stderr, "semaphore_p failed/n");
        return 0;
    }
    printf("semaphore_p [%d]is over\n", get_semvalue(sem_id));

    return 1;
}


static int semaphore_v(int sem_id)
{
    sem_b.sem_num = 0;
    sem_b.sem_op = 1;
    sem_b.sem_flg = SEM_UNDO;
    printf("semaphore_v [%d]is begin\n", get_semvalue(sem_id));
    if(semop(sem_id, &sem_b, 1) == -1)
    {
        fprintf(stderr, "semaphore_v failed/n");
        return 0;
    }
    printf("semaphore_v [%d]is over\n", get_semvalue(sem_id));
    return 1;
}

static int semaphore_wait(int sem_id)
{
    sem_b.sem_num = 0;
    sem_b.sem_op = 0;
    sem_b.sem_flg = SEM_UNDO;
    printf("I am waiting\n");
    printf("SEM is %d\n",get_semvalue(sem_id));
    if(semop(sem_id, &sem_b, 1) == -1)
    {
        fprintf(stderr, "semaphore_v failed/n");
        return 0;
    }
    printf("I am coming\n");
    return 1;
}

void * fun(void)
{

        semaphore_v(sem_id_2);
        semaphore_v(sem_id_2);

}

int main()
{
    sem_id_2 = semget((key_t)4321, 1, 0666 | IPC_CREAT);
    int r;
    if((r=set_semvalue(sem_id_2,0))<0 )
    {
        fprintf(stderr, "Failed to initialize semaphore%d\n",r);
    }

    printf("SEM2 is %d\n",get_semvalue(sem_id_2));
    pthread_t consume_tid;

    pthread_create(&consume_tid, NULL, fun, NULL);

    printf("main is waiting\n");
    semaphore_p(sem_id_2,2);
    printf("ALL is over\n");
    pthread_join(consume_tid, NULL);
    return 1;
}




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