上下文:Ubuntu 11.10 和 libfuse 2.8.4-1.4ubuntu1 Linux 3.0.0-14-generic #23-Ubuntu SMP Mon Nov 21 20:28:43 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux
我正在尝试使用 libfuse。我想让 fuse_session_loop 退出(从信号处理程序或不同的线程),但是当我调用 fuse_session_exit 时,在会话收到新请求之前什么都不会发生。
fuse_session_exit 设置一个由 fuse_session_exited 读取的标志。调试到 fuse_session_loop 它似乎阻塞了 fuse_chan_recv,所以它不会再次检查 fuse_session_exited 直到循环的顶部......
int fuse_session_loop(struct fuse_session *se)
{
int res = 0;
struct fuse_chan *ch = fuse_session_next_chan(se, NULL);
size_t bufsize = fuse_chan_bufsize(ch);
char *buf = (char *) malloc(bufsize);
if (!buf) {
fprintf(stderr, "fuse: failed to allocate read buffer\n");
return -1;
}
while (!fuse_session_exited(se)) {
struct fuse_chan *tmpch = ch;
res = fuse_chan_recv(&tmpch, buf, bufsize); <--- BLOCKING
if (res == -EINTR)
continue;
if (res <= 0)
break;
fuse_session_process(se, buf, res, tmpch);
}
free(buf);
fuse_session_reset(se);
return res < 0 ? -1 : 0;
}
fuse_chan_recv 调用 fuse_kern_chan_receive 阻塞“/dev/fuse”设备的“read”系统调用,因此即使设置了 fuse_session_exited 标志,也没有任何反应。
static int fuse_kern_chan_receive(struct fuse_chan **chp, char *buf,
size_t size)
{
struct fuse_chan *ch = *chp;
int err;
ssize_t res;
struct fuse_session *se = fuse_chan_session(ch);
assert(se != NULL);
restart:
res = read(fuse_chan_fd(ch), buf, size); <--- BLOCKING
err = errno;
if (fuse_session_exited(se))
return 0;
if (res == -1) {
/* ENOENT means the operation was interrupted, it's safe
to restart */
if (err == ENOENT)
goto restart;
if (err == ENODEV) {
fuse_session_exit(se);
return 0;
}
/* Errors occuring during normal operation: EINTR (read
interrupted), EAGAIN (nonblocking I/O), ENODEV (filesystem
umounted) */
if (err != EINTR && err != EAGAIN)
perror("fuse: reading device");
return -err;
}
if ((size_t) res < sizeof(struct fuse_in_header)) {
fprintf(stderr, "short read on fuse device\n");
return -EIO;
}
return res;
}
这个问题似乎影响了 libfuse 提供的 hello_ll.c 示例以及我的程序。这让我觉得也许有一些机制不应该起作用。也许 fuse_session_exit 也应该做一些中断读取调用的事情,由于某种原因在我的系统上不起作用。
有任何想法吗?