在 Linux 中实现 WaitForSingleObject(GetCurrentThread(),INFINITE)

Question

我想知道为什么

pthread_join(pthread_self(),NULL)

会导致未定义的行为，但

WaitForSingleObject(GetCurrentThread(),INFINITE)

没问题？

另外，如果我想替换

WaitForSingleObject(GetCurrentThread(),INFINITE)

以在 Linux 中正常工作，有什么等效的吗？

我正在尝试实现一个用 Windows 调用 Linux 编写的代码。我被困在这条线上，找不到问题的答案。

Answer 1

pthread_join()

等待指定线程终止。

pthread_join(pthread_self(), NULL)

将尝试等待调用者线程终止，这永远不会发生。这是明显的死锁，并且它具有定义的行为：返回

EDEADLK

错误。来自 man pthread_join：

EDEADLK 检测到死锁（例如，两个线程试图相互连接）；或 thread 指定调用线程。

如果需要等待多个线程终止，可以按顺序join所有线程。加入顺序并不重要。代码示例：

#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>
#include <stdint.h>
#include <time.h>

static void *worker(void *arg)
{
    int idx = (intptr_t)arg;
    printf("thread %i: started\n", idx);

    /* Some pseudo-random delay 1..1000 ms */
    struct timespec ts;
    ts.tv_sec = 0;
    ts.tv_nsec = 1000000l * (1 + rand() % 1000);
    nanosleep(&ts, NULL);

    printf("thread %i: exiting\n", idx);
    return NULL;
}

int main(void)
{
    srand(time(NULL));

    pthread_t threads[5];
    const int num_threads = sizeof(threads)/sizeof(*threads);

    for (int i = 0; i < num_threads; ++i)
    {
        void *arg = (void *)(intptr_t)i;
        int err = pthread_create(threads + i, NULL, worker, arg);
        if (err != 0)
            abort();
    }

    for (int i = 0; i < num_threads; ++i)
    {
        printf("main: waiting for thread %i\n", i);

        int err = pthread_join(threads[i], NULL);
        if (err != 0)
            abort();

        printf("main: thread %i terminated\n", i);
    }

    printf("main: all threads exited\n");

    return 0;
}

可能的输出：

thread 0: started
thread 1: started
thread 2: started
main: waiting for thread 0
thread 3: started
thread 4: started
thread 0: exiting
main: thread 0 terminated
main: waiting for thread 1
thread 4: exiting
thread 1: exiting
main: thread 1 terminated
main: waiting for thread 2
thread 3: exiting
thread 2: exiting
main: thread 2 terminated
main: waiting for thread 3
main: thread 3 terminated
main: waiting for thread 4
main: thread 4 terminated
main: all threads exited