[PATCH liburing 1/2] handle single issuer task registration at ring creation

[Dylan Yudaken <dylany@fb.com>]

IORING_SETUP_SINGLE_ISSUER now registers the task at ring creation, so
update the tests and documentation to reflect this.

Signed-off-by: Dylan Yudaken <dylany@fb.com>
---
 man/io_uring_setup.2 |  8 ++++----
 test/defer-taskrun.c | 12 ++++--------
 test/single-issuer.c | 14 +++++++-------
 3 files changed, 15 insertions(+), 19 deletions(-)

diff --git a/man/io_uring_setup.2 b/man/io_uring_setup.2
index fb1f90dc2ebc..afeee858c458 100644
--- a/man/io_uring_setup.2
+++ b/man/io_uring_setup.2
@@ -241,14 +241,14 @@ only the
 passthrough command for NVMe passthrough needs this. Available since 5.19.
 .TP
 .B IORING_SETUP_SINGLE_ISSUER
-A hint to the kernel that only a single task can submit requests, which is used
-for internal optimisations. The kernel enforces the rule, which only affects
+A hint to the kernel that only a single task (or thread) will submit requests, which is
+used for internal optimisations. This task must be the one that created the ring, and
+the kernel enforces this rule. This only affects
 .I
 io_uring_enter(2)
 calls submitting requests and will fail them with
 .B -EEXIST
 if the restriction is violated.
-The submitter task may differ from the task that created the ring.
 Note that when
 .B IORING_SETUP_SQPOLL
 is set it is considered that the polling task is doing all submissions
@@ -256,7 +256,7 @@ on behalf of the userspace and so it always complies with the rule disregarding
 how many userspace tasks do
 .I
 io_uring_enter(2).
-Available since 5.20.
+Available since 6.0.
 .TP
 .B IORING_SETUP_DEFER_TASKRUN
 By default, io_uring will process all outstanding work at the end of any system
diff --git a/test/defer-taskrun.c b/test/defer-taskrun.c
index c6e0ea0d6c99..2c4ed6df37d3 100644
--- a/test/defer-taskrun.c
+++ b/test/defer-taskrun.c
@@ -123,6 +123,9 @@ void *thread(void *t)
 {
 	struct thread_data *td = t;
 
+	assert(io_uring_queue_init(8, &td->ring, IORING_SETUP_SINGLE_ISSUER |
+					IORING_SETUP_DEFER_TASKRUN) == 0);
+
 	io_uring_prep_read(io_uring_get_sqe(&td->ring), td->efd, td->buff, sizeof(td->buff), 0);
 	io_uring_submit(&td->ring);
 
@@ -132,23 +135,16 @@ void *thread(void *t)
 static int test_thread_shutdown(void)
 {
 	pthread_t t1;
-	int ret;
 	struct thread_data td;
 	struct io_uring_cqe *cqe;
 	uint64_t val = 1;
 
-	ret = io_uring_queue_init(8, &td.ring, IORING_SETUP_SINGLE_ISSUER |
-					       IORING_SETUP_DEFER_TASKRUN);
-	if (ret)
-		return ret;
-
-	CHECK(io_uring_get_events(&td.ring) == -EEXIST);
-
 	td.efd = eventfd(0, 0);
 	CHECK(td.efd >= 0);
 
 	CHECK(pthread_create(&t1, NULL, thread, &td) == 0);
 	CHECK(pthread_join(t1, NULL) == 0);
+	CHECK(io_uring_get_events(&td.ring) == -EEXIST);
 
 	CHECK(write(td.efd, &val, sizeof(val)) == sizeof(val));
 	CHECK(io_uring_wait_cqe(&td.ring, &cqe) == -EEXIST);
diff --git a/test/single-issuer.c b/test/single-issuer.c
index 29830f1af998..55af98f300aa 100644
--- a/test/single-issuer.c
+++ b/test/single-issuer.c
@@ -96,7 +96,7 @@ int main(int argc, char *argv[])
 	if (!fork_t()) {
 		ret = try_submit(&ring);
 		if (ret != -EEXIST)
-			fprintf(stderr, "not owner child could submit %i\n", ret);
+			fprintf(stderr, "1: not owner child could submit %i\n", ret);
 		return ret != -EEXIST;
 	}
 	wait_child_t();
@@ -109,9 +109,9 @@ int main(int argc, char *argv[])
 
 	if (!fork_t()) {
 		ret = try_submit(&ring);
-		if (ret)
-			fprintf(stderr, "not owner child could submit %i\n", ret);
-		return !!ret;
+		if (ret != -EEXIST)
+			fprintf(stderr, "2: not owner child could submit %i\n", ret);
+		return ret != -EEXIST;
 	}
 	wait_child_t();
 	io_uring_queue_exit(&ring);
@@ -143,9 +143,9 @@ int main(int argc, char *argv[])
 
 	if (!fork_t()) {
 		ret = try_submit(&ring);
-		if (ret)
-			fprintf(stderr, "not owner child could submit %i\n", ret);
-		return !!ret;
+		if (ret != -EEXIST)
+			fprintf(stderr, "3: not owner child could submit %i\n", ret);
+		return ret != -EEXIST;
 	}
 	wait_child_t();
 	io_uring_queue_exit(&ring);
-- 
2.30.2