为什么FUSE似乎锁定了所有线程？

Question

我拿了保险丝hello.c并修改了底部以显示我在说什么.在我的应用程序中,我需要在保险丝FS可用后做一些事情.我还需要IPC的另一个线程,并保持某些事情是最新的.因为fuse_main似乎没有返回我把它扔在自己的线程中.

当我注释掉fuse_main控制台显示A和B打印时.但是,如果我没有注释掉fuse_main(在不同的主题中),则仅打印A. 如何保险丝停止我的主线程以及如何在FUSE执行其操作后运行代码？

#define FUSE_USE_VERSION 26

#include <fuse.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>

static const char *hello_str = "Hello World!\n";
static const char *hello_path = "/hello";

static int hello_getattr(const char *path, struct stat *stbuf)
{
    int res = 0;

    memset(stbuf, 0, sizeof(struct stat));
    if (strcmp(path, "/") == 0) {
        stbuf->st_mode = S_IFDIR | 0755;
        stbuf->st_nlink = 2;
    } else if (strcmp(path, hello_path) == 0) {
        stbuf->st_mode = S_IFREG | 0444;
        stbuf->st_nlink = 1;
        stbuf->st_size = strlen(hello_str);
    } else
        res = -ENOENT;

    return res;
}

static int hello_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
             off_t offset, struct fuse_file_info *fi)
{
    (void) offset;
    (void) fi;

    if (strcmp(path, "/") != 0)
        return -ENOENT;

    filler(buf, ".", NULL, 0);
    filler(buf, "..", NULL, 0);
    filler(buf, hello_path + 1, NULL, 0);

    return 0;
}

static int hello_open(const char *path, struct fuse_file_info *fi)
{
    if (strcmp(path, hello_path) != 0)
        return -ENOENT;

    if ((fi->flags & 3) != O_RDONLY)
        return -EACCES;

    return 0;
}

static int hello_read(const char *path, char *buf, size_t size, off_t offset,
              struct fuse_file_info *fi)
{
    size_t len;
    (void) fi;
    if(strcmp(path, hello_path) != 0)
        return -ENOENT;

    len = strlen(hello_str);
    if (offset < len) {
        if (offset + size > len)
            size = len - offset;
        memcpy(buf, hello_str + offset, size);
    } else
        size = 0;

    return size;
}

static struct fuse_operations hello_oper;
//modification starts below this line
#include<thread>
#include<unistd.h>
int main(int argc, char *argv[])
{
    std::thread t([&]{
        hello_oper.getattr  = hello_getattr;
        hello_oper.readdir  = hello_readdir;
        hello_oper.open     = hello_open;
        hello_oper.read     = hello_read;

        return fuse_main(argc, argv, &hello_oper, NULL);
    });
    printf("A\n");
    sleep(5);
    printf("B\n");
    t.join();
}

Answer 1

fuse_main守护进程,即父进程中的调用fork()和调用_exit(0),因此进程退出,因此您只能看到A打印输出.

如果你给的选项-f中./hello -f /tmp/fuse的fuse_main不叫_exit,但在前台停留活着,都A和B可以看到.

fuse_main当程序想要退出时,你肯定需要一种方法来优雅地结束线程:

//modification starts below this line
#include<thread>
#include<unistd.h>
#include <signal.h>
#include <sys/syscall.h>

int main(int argc, char *argv[])
{
    pid_t tid;
    std::thread t([&]{
        hello_oper.getattr  = hello_getattr;
        hello_oper.readdir  = hello_readdir;
        hello_oper.open     = hello_open;
        hello_oper.read     = hello_read;

        tid = syscall(SYS_gettid);
        return fuse_main(argc, argv, &hello_oper, NULL);
    });
    printf("A\n");
    sleep(5);
    printf("B\n");
    kill(tid, SIGTERM);
    t.join();
}

选项hello:

general options:
    -o opt,[opt...]        mount options
    -h   --help            print help
    -V   --version         print version

FUSE options:
    -d   -o debug          enable debug output (implies -f)
    -f                     foreground operation
    -s                     disable multi-threaded operation
[...]