selftests/bpf: wq: add bpf_wq_start() checks

Allows to test if allocation/free works
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
Link: https://lore.kernel.org/r/20240420-bpf_wq-v2-16-6c986a5a741f@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/bpf_experimental.h

@@ -471,6 +471,7 @@ extern struct cgroup_subsys_state *bpf_iter_css_next(struct bpf_iter_css *it) __
 extern void bpf_iter_css_destroy(struct bpf_iter_css *it) __weak __ksym;
 
 extern int bpf_wq_init(struct bpf_wq *wq, void *p__map, unsigned int flags) __weak __ksym;
+extern int bpf_wq_start(struct bpf_wq *wq, unsigned int flags) __weak __ksym;
 extern int bpf_wq_set_callback_impl(struct bpf_wq *wq,
 		int (callback_fn)(void *map, int *key, struct bpf_wq *wq),
 		unsigned int flags__k, void *aux__ign) __ksym;

tools/testing/selftests/bpf/prog_tests/wq.c

@@ -6,9 +6,31 @@
 
 void serial_test_wq(void)
 {
+	struct wq *wq_skel = NULL;
+	int err, prog_fd;
+
 	LIBBPF_OPTS(bpf_test_run_opts, topts);
 
 	RUN_TESTS(wq);
+
+	/* re-run the success test to check if the timer was actually executed */
+
+	wq_skel = wq__open_and_load();
+	if (!ASSERT_OK_PTR(wq_skel, "wq_skel_load"))
+		return;
+
+	err = wq__attach(wq_skel);
+	if (!ASSERT_OK(err, "wq_attach"))
+		return;
+
+	prog_fd = bpf_program__fd(wq_skel->progs.test_syscall_array_sleepable);
+	err = bpf_prog_test_run_opts(prog_fd, &topts);
+	ASSERT_OK(err, "test_run");
+	ASSERT_EQ(topts.retval, 0, "test_run");
+
+	usleep(50); /* 10 usecs should be enough, but give it extra */
+
+	ASSERT_EQ(wq_skel->bss->ok_sleepable, (1 << 1), "ok_sleepable");
 }
 
 void serial_test_failures_wq(void)

tools/testing/selftests/bpf/progs/wq.c

@@ -49,12 +49,19 @@ struct {
 	__type(value, struct elem);
 } lru SEC(".maps");
 
+__u32 ok;
+__u32 ok_sleepable;
+
 static int test_elem_callback(void *map, int *key,
 		int (callback_fn)(void *map, int *key, struct bpf_wq *wq))
 {
 	struct elem init = {}, *val;
 	struct bpf_wq *wq;
 
+	if ((ok & (1 << *key) ||
+	    (ok_sleepable & (1 << *key))))
+		return -22;
+
 	if (map == &lru &&
 	    bpf_map_update_elem(map, key, &init, 0))
 		return -1;
@@ -70,6 +77,9 @@ static int test_elem_callback(void *map, int *key,
 	if (bpf_wq_set_callback(wq, callback_fn, 0))
 		return -4;
 
+	if (bpf_wq_start(wq, 0))
+		return -5;
+
 	return 0;
 }
 
@@ -79,6 +89,10 @@ static int test_hmap_elem_callback(void *map, int *key,
 	struct hmap_elem init = {}, *val;
 	struct bpf_wq *wq;
 
+	if ((ok & (1 << *key) ||
+	    (ok_sleepable & (1 << *key))))
+		return -22;
+
 	if (bpf_map_update_elem(map, key, &init, 0))
 		return -1;
 
@@ -93,12 +107,12 @@ static int test_hmap_elem_callback(void *map, int *key,
 	if (bpf_wq_set_callback(wq, callback_fn, 0))
 		return -4;
 
+	if (bpf_wq_start(wq, 0))
+		return -5;
+
 	return 0;
 }
 
-__u32 ok;
-__u32 ok_sleepable;
-
 /* callback for non sleepable workqueue */
 static int wq_callback(void *map, int *key, struct bpf_wq *work)
 {