Pthread 条件变量即使设置为 PTHREAD_PROCESS_SHARED，也不会发出信号

您在子进程中不必要地截断互斥锁和条件变量的共享内存。由于这部分曾经发生在原始代码中的 fork(( 之前，因此您只为这对夫妇做了一次。但是在两个单独的进程中，您将分别在父亲中使用跨进程 pthread 互斥锁和条件变量初始化共享内存，然后通过使用儿子中的 O_TRUNC 销毁 pthread 放入其中的所有内容。正确的代码如下：

父亲.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>
#define OKTOWRITE "/condwrite"
#define MESSAGE "/msg"
#define MUTEX "/mutex_lock"
int main(int argc, char *argv[])
{
    pthread_cond_t* condition;
    pthread_mutex_t* mutex;
    char* message;
    int des_cond, des_msg, des_mutex;
    int mode = S_IRWXU | S_IRWXG;
    des_mutex = shm_open(MUTEX, O_CREAT | O_RDWR | O_TRUNC, mode);
    if (des_mutex < 0) {
        perror("failure on shm_open on des_mutex");
        exit(1);
    }
    if (ftruncate(des_mutex, sizeof(pthread_mutex_t)) == -1) {
        perror("Error on ftruncate to sizeof pthread_cond_tn");
        exit(-1);
    }
    mutex = (pthread_mutex_t*) mmap(NULL, sizeof(pthread_mutex_t),
            PROT_READ | PROT_WRITE, MAP_SHARED, des_mutex, 0);
    if (mutex == MAP_FAILED ) {
        perror("Error on mmap on mutexn");
        exit(1);
    }
    des_cond = shm_open(OKTOWRITE, O_CREAT | O_RDWR | O_TRUNC, mode);
    if (des_cond < 0) {
        perror("failure on shm_open on des_cond");
        exit(1);
    }
    if (ftruncate(des_cond, sizeof(pthread_cond_t)) == -1) {
        perror("Error on ftruncate to sizeof pthread_cond_tn");
        exit(-1);
    }
    condition = (pthread_cond_t*) mmap(NULL, sizeof(pthread_cond_t),
            PROT_READ | PROT_WRITE, MAP_SHARED, des_cond, 0);
    if (condition == MAP_FAILED ) {
        perror("Error on mmap on conditionn");
        exit(1);
    }
    /* HERE WE GO */
    /**************************************/
        /* set mutex shared between processes */
    pthread_mutexattr_t mutexAttr;
    pthread_mutexattr_init(&mutexAttr);
    pthread_mutexattr_setpshared(&mutexAttr, PTHREAD_PROCESS_SHARED);
    pthread_mutex_init(mutex, &mutexAttr);
    /* set condition shared between processes */
    pthread_condattr_t condAttr;
    pthread_condattr_init(&condAttr);
    pthread_condattr_setpshared(&condAttr, PTHREAD_PROCESS_SHARED);
    pthread_cond_init(condition, &condAttr);
    /*************************************/

    printf("father waits on conditionn");
     pthread_mutex_lock(mutex);
     pthread_cond_wait(condition, mutex);
     pthread_mutex_unlock(mutex);
     printf("Signaled by son process, wake up!!!!!!!!n");
    pthread_condattr_destroy(&condAttr);
    pthread_mutexattr_destroy(&mutexAttr);
    pthread_mutex_destroy(mutex);
    pthread_cond_destroy(condition);
    shm_unlink(OKTOWRITE);
    shm_unlink(MESSAGE);
    shm_unlink(MUTEX);
    exit(0);
}

儿子

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>
#define OKTOWRITE "/condwrite"
#define MESSAGE "/msg"
#define MUTEX "/mutex_lock"
int main(int argc, char *argv[])
{
    pthread_cond_t* condition;
    pthread_mutex_t* mutex;
    char* message;
    int des_cond, des_msg, des_mutex;
    int mode = S_IRWXU | S_IRWXG;
    des_mutex = shm_open(MUTEX, O_CREAT | O_RDWR, mode);
    if (des_mutex < 0) {
        perror("failure on shm_open on des_mutex");
        exit(1);
    }
    mutex = (pthread_mutex_t*) mmap(NULL, sizeof(pthread_mutex_t),
            PROT_READ | PROT_WRITE, MAP_SHARED, des_mutex, 0);
    if (mutex == MAP_FAILED ) {
        perror("Error on mmap on mutexn");
        exit(1);
    }
    des_cond = shm_open(OKTOWRITE, O_CREAT | O_RDWR, mode);
    if (des_cond < 0) {
        perror("failure on shm_open on des_cond");
        exit(1);
    }
    condition = (pthread_cond_t*) mmap(NULL, sizeof(pthread_cond_t),
            PROT_READ | PROT_WRITE, MAP_SHARED, des_cond, 0);
    if (condition == MAP_FAILED ) {
        perror("Error on mmap on conditionn");
        exit(1);
    }
    pthread_mutex_lock(mutex);
    pthread_cond_signal(condition);
    printf("son signaledn");
    pthread_mutex_unlock(mutex);
    exit(0);
}

测试：

1st terminal: $ ./father
father waits on condition
2nd terminal: $ ./son
son signaled
1st terminal: Signaled by son process, wake up!!!!!!!!
$