io_uring process termination/killing is not working

Josef
2020-08-12T17:59:00Z

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Hi,

I have a weird issue on kernel 5.8.0/5.8.1, SIGINT even SIGKILL
doesn't work to kill this process(always state D or D+), literally I
have to terminate my VM because even the kernel can't kill the process
and no issue on 5.7.12-201, however if IOSQE_IO_LINK is not set, it
works

I've attached a file to reproduce it
or here
https://gist.github.com/1Jo1/15cb3c63439d0c08e3589cfa98418b2c

---
Josef

[-- Attachment #2: io_uring_process.c --]
[-- Type: application/octet-stream, Size: 1878 bytes --]

#include <errno.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <sys/socket.h>
#include <unistd.h>
#include <poll.h>
#include "liburing.h"

#define BACKLOG 512

#define PORT 9100

struct io_uring ring;

void add_poll(struct io_uring *ring, int fd) {
struct io_uring_sqe *sqe = io_uring_get_sqe(ring);
io_uring_prep_poll_add(sqe, fd, POLLIN);
sqe->flags |= IOSQE_IO_LINK;
}

void add_accept(struct io_uring *ring, int fd) {
struct io_uring_sqe *sqe = io_uring_get_sqe(ring);
io_uring_prep_accept(sqe, fd, 0, 0, SOCK_NONBLOCK | SOCK_CLOEXEC);
sqe->flags |= IOSQE_IO_LINK;
}

int setup_io_uring() {
int ret = io_uring_queue_init(16, &ring, 0);
if (ret) {
fprintf(stderr, "Unable to setup io_uring: %s\n", strerror(-ret));
return 1;
}
return 0;
}

int main(int argc, char *argv[]) {

struct sockaddr_in serv_addr;

setup_io_uring();

int sock_listen_fd = socket(AF_INET, SOCK_STREAM | SOCK_NONBLOCK, 0);
const int val = 1;
setsockopt(sock_listen_fd, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));

memset(&serv_addr, 0, sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(PORT);
serv_addr.sin_addr.s_addr = INADDR_ANY;

if (bind(sock_listen_fd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) {
perror("Error binding socket\n");
exit(1);
}
if (listen(sock_listen_fd, BACKLOG) < 0) {
perror("Error listening on socket\n");
exit(1);
}

setup_io_uring();

add_poll(&ring, sock_listen_fd);
add_accept(&ring, sock_listen_fd);
io_uring_submit(&ring);

while (1) {
struct io_uring_cqe *cqe;
io_uring_wait_cqe(&ring, &cqe);

}

io_uring_queue_exit(&ring);

return 0;
}