[PATCH liburing] Add a test that ensures unregistering is reasonably quick

[PATCH liburing] Add a test that ensures unregistering is reasonably quick

[Dylan Yudaken]

There was a bug [1] in io_uring that caused a 1 second delay on shutdown
due to how registered resources were cleaned up. This test exposes the
bug, and verifies that it does not reoccur. While time based tests have
the potential to be flaky, locally with the fix it completes in 5ms, and
so I do not expect this to be a practical problem.

[1]: https://lore.kernel.org/io-uring/20220121123856.3557884-1-dylany@fb.com/T/#u

Signed-off-by: Dylan Yudaken <dylany@fb.com>
---
 test/io_uring_register.c | 46 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)

diff --git a/test/io_uring_register.c b/test/io_uring_register.c
index b8a4ea5..8bf0fd3 100644
--- a/test/io_uring_register.c
+++ b/test/io_uring_register.c
@@ -609,6 +609,50 @@ out:
 	return 0;
 }
 
+static size_t timeus(struct timespec t)
+{
+	return (size_t)t.tv_sec * 1000000 + t.tv_nsec / 1000;
+}
+
+static int
+test_unregister_speed(void)
+{
+	struct timespec start, end;
+	struct io_uring_params p;
+	int fd, ret;
+	struct iovec iov;
+	size_t diff;
+	void *buf;
+
+	memset(&p, 0, sizeof(p));
+	fd = new_io_uring(1, &p);
+
+	buf = t_malloc(pagesize);
+	iov.iov_base = buf;
+	iov.iov_len = pagesize;
+
+	ret = __sys_io_uring_register(fd, IORING_REGISTER_BUFFERS, &iov, 1);
+	if (ret) {
+		fprintf(stderr, "error registering buffers\n");
+		goto done;
+	}
+
+	clock_gettime(CLOCK_MONOTONIC_RAW, &start);
+	__sys_io_uring_register(fd, IORING_UNREGISTER_BUFFERS, 0, 0);
+	clock_gettime(CLOCK_MONOTONIC_RAW, &end);
+	diff = timeus(end) - timeus(start);
+
+	/* 500ms should be enough to deregister any buffers */
+	ret =  diff > 500000 ? -1 : 0;
+
+	fprintf(stderr, "took %lu us to unregister buffers: %s\n",
+		diff, ret ? "FAIL" : "PASS");
+done:
+	free(buf);
+	close(fd);
+	return ret;
+}
+
 int
 main(int argc, char **argv)
 {
@@ -660,6 +704,8 @@ main(int argc, char **argv)
 	/* uring poll on the uring fd */
 	status |= test_poll_ringfd();
 
+	status |= test_unregister_speed();
+
 	if (!status)
 		printf("PASS\n");
 	else

base-commit: bbcaabf808b53ef11ad9851c6b968140fb430500
-- 
2.30.2