[PATCH bpf-next] selftests/bpf: Wait for the struct_ops map to be freed in assoc_in_timer

[Qiliang Yuan]

st_ops_assoc_in_timer_no_uref runs .test_1, which starts a timer to
call it again 500ms later, drops every reference to the struct_ops map,
and expects the timer callback to find no struct_ops associated with
its program anymore.

The association goes away only when the map is freed, which happens in
a work item after an RCU grace period. With other tests running in
parallel, that can take longer than 500ms, and the callback still
reaches the struct_ops and gets MAP_MAGIC instead of -1.

Restart the timer from its callback until the map is gone.

Fixes: 0e841d19263a ("selftests/bpf: Test getting associated struct_ops in timer callback")
Signed-off-by: Qiliang Yuan <odys.yuan@xxxxxxxxx>
---
 tools/testing/selftests/bpf/prog_tests/test_struct_ops_assoc.c | 4 +++-
 tools/testing/selftests/bpf/progs/struct_ops_assoc_in_timer.c  | 7 +++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/test_struct_ops_assoc.c b/tools/testing/selftests/bpf/prog_tests/test_struct_ops_assoc.c
index 461ded7223515..84da2c8651bec 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_struct_ops_assoc.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_struct_ops_assoc.c
@@ -158,9 +158,11 @@ static void test_st_ops_assoc_in_timer_no_uref(void)
 	 * Run .test_1 by calling kfunc bpf_kfunc_multi_st_ops_test_1_prog_arg() and checks
 	 * the return value. .test_1 will also schedule timer_cb that runs .test_1 again.
 	 * timer_cb will run 500ms after syscall_prog runs, when the user space no longer
-	 * holds a reference to st_ops_map.
+	 * holds a reference to st_ops_map, and every 500ms after that until the map is
+	 * freed.
 	 */
 	skel->bss->timer_ns = 500000000;
+	skel->bss->wait_map_free = 1;
 	err = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.syscall_prog), NULL);
 	ASSERT_OK(err, "bpf_prog_test_run_opts");
 
diff --git a/tools/testing/selftests/bpf/progs/struct_ops_assoc_in_timer.c b/tools/testing/selftests/bpf/progs/struct_ops_assoc_in_timer.c
index 0bed49e9f2170..9f3124acd9b04 100644
--- a/tools/testing/selftests/bpf/progs/struct_ops_assoc_in_timer.c
+++ b/tools/testing/selftests/bpf/progs/struct_ops_assoc_in_timer.c
@@ -25,6 +25,7 @@ int test_err;
 int timer_ns;
 int timer_test_1_ret;
 int timer_cb_run;
+int wait_map_free;
 
 __noinline static int timer_cb(void *map, int *key, struct bpf_timer *timer)
 {
@@ -34,6 +35,12 @@ __noinline static int timer_cb(void *map, int *key, struct bpf_timer *timer)
 	timer_test_1_ret = bpf_kfunc_multi_st_ops_test_1_assoc(&args);
 	recur--;
 
+	/* Try again later until the map is freed */
+	if (wait_map_free && timer_test_1_ret != -1) {
+		bpf_timer_start(timer, timer_ns, 0);
+		return 0;
+	}
+
 	timer_cb_run++;
 
 	return 0;

---
base-commit: e1d84a37cba984388988d2f1ddc84561413f0db2
change-id: 20261009-selftests-bpf-struct-ops-assoc-timer-5eb0295ec300

Best regards,
-- 
Qiliang Yuan <odys.yuan@xxxxxxxxx>