Re: [PATCH v4 0/1] io_uring: fix skipping of old timeout events

[Marcelo Diop-Gonzalez <marcelo827@gmail.com>]

On Fri, Jan 15, 2021 at 10:02:12AM -0700, Jens Axboe wrote:
> On 1/15/21 9:54 AM, Marcelo Diop-Gonzalez wrote:
> > This patch tries to fix a problem with IORING_OP_TIMEOUT events
> > not being flushed if they should already have expired. The test below
> > hangs before this change (unless you run with $ ./a.out ~/somefile 1):
> > 
> > #include <fcntl.h>
> > #include <stdio.h>
> > #include <stdlib.h>
> > #include <string.h>
> > #include <unistd.h>
> > 
> > #include <liburing.h>
> > 
> > int main(int argc, char **argv) {
> > 	if (argc < 2)
> > 		return 1;
> > 
> > 	int fd = open(argv[1], O_RDONLY);
> > 	if (fd < 0) {
> > 		perror("open");
> > 		return 1;
> > 	}
> > 
> > 	struct io_uring ring;
> > 	io_uring_queue_init(4, &ring, 0);
> > 
> > 	struct io_uring_sqe *sqe = io_uring_get_sqe(&ring);
> > 
> > 	struct __kernel_timespec ts = { .tv_sec = 9999999 };
> > 	io_uring_prep_timeout(sqe, &ts, 1, 0);
> > 	sqe->user_data = 123;
> > 	int ret = io_uring_submit(&ring);
> > 	if (ret < 0) {
> > 		fprintf(stderr, "submit(timeout_sqe): %d\n", ret);
> > 		return 1;
> > 	}
> > 
> > 	int n = 2;
> > 	if (argc > 2)
> > 		n = atoi(argv[2]);
> > 
> > 	char buf;
> > 	for (int i = 0; i < n; i++) {
> > 		sqe = io_uring_get_sqe(&ring);
> > 		if (!sqe) {
> > 			fprintf(stderr, "too many\n");
> > 			exit(1);
> > 		}
> > 		io_uring_prep_read(sqe, fd, &buf, 1, 0);
> > 	}
> > 	ret = io_uring_submit(&ring);
> > 	if (ret < 0) {
> > 		fprintf(stderr, "submit(read_sqe): %d\n", ret);
> > 		exit(1);
> > 	}
> > 
> > 	struct io_uring_cqe *cqe;
> > 	for (int i = 0; i < n+1; i++) {
> > 		struct io_uring_cqe *cqe;
> > 		int ret = io_uring_wait_cqe(&ring, &cqe);
> > 		if (ret < 0) {
> > 			fprintf(stderr, "wait_cqe(): %d\n", ret);
> > 			return 1;
> > 		}
> > 		if (cqe->user_data == 123)
> > 			printf("timeout found\n");
> > 		io_uring_cqe_seen(&ring, cqe);
> > 	}
> > }
> 
> Can you turn this into a test case for liburing? I'll apply the
> associated patch, thanks (and to Pavel for review as well).

Yup, can do. I'll try to clean it up some first (especially so it
doesn't just hang when it fails :/)

> 
> -- 
> Jens Axboe
>