[PATCH bpf-next 3/4] selftests/bpf: add thread_wq cgroup test

From: Hui Zhu <[email protected]>

Add test cases for bpf_thread_wq with cgroup attachment:

- Test thread_wq execution in a specified cgroup and verify
  callback runs in the target cgroup
- Test thread_wq execution without cgroup attachment and verify
  callback runs in a different cgroup

This validates that bpf_thread_wq properly attaches to and
executes callbacks within the specified cgroup context.

Signed-off-by: Hui Zhu <[email protected]>
---
 .../bpf/prog_tests/thread_wq_cgroup.c         | 87 +++++++++++++++++++
 .../selftests/bpf/progs/thread_wq_cgroup.c    | 56 ++++++++++++
 2 files changed, 143 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/thread_wq_cgroup.c
 create mode 100644 tools/testing/selftests/bpf/progs/thread_wq_cgroup.c

diff --git a/tools/testing/selftests/bpf/prog_tests/thread_wq_cgroup.c b/tools/testing/selftests/bpf/prog_tests/thread_wq_cgroup.c
new file mode 100644
index 000000000000..7537b03f17e2
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/thread_wq_cgroup.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include <unistd.h>
+#include "cgroup_helpers.h"
+#include "thread_wq_cgroup.skel.h"
+
+#define TEST_CGROUP "/thread_wq_test"
+#define WAIT_TIMEOUT_SECS 30
+
+void test_thread_wq_cgroup(void)
+{
+	struct thread_wq_cgroup *skel = NULL;
+	int err, prog_fd, cg_fd = -1;
+	unsigned long long cg_id;
+	int waited_secs;
+
+	LIBBPF_OPTS(bpf_test_run_opts, topts);
+
+	err = setup_cgroup_environment();
+	if (!ASSERT_OK(err, "setup_cgroup_environment"))
+		return;
+	cg_fd = create_and_get_cgroup(TEST_CGROUP);
+	if (!ASSERT_GE(cg_fd, 0, "create_and_get_cgroup"))
+		goto cleanup;
+	cg_id = get_cgroup_id(TEST_CGROUP);
+	if (!ASSERT_GT(cg_id, 0ULL, "get_cgroup_id"))
+		goto cleanup;
+
+	skel = thread_wq_cgroup__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "open_and_load"))
+		goto cleanup;
+
+	prog_fd = bpf_program__fd(skel->progs.start_thread_wq);
+
+	/* Run bpf_thread_wq in the specified cgroup. */
+	skel->bss->test_key = 0;
+	skel->bss->target_cgroup_id = cg_id;
+	skel->bss->callback_cgroup_id = 0;
+	skel->bss->twq_done = 0;
+	if (!ASSERT_OK(bpf_prog_test_run_opts(prog_fd, &topts),
+		       "bpf_prog_test_run_opts in cgroup"))
+		goto cleanup;
+	if (!ASSERT_OK(topts.retval, "retval in cgroup"))
+		goto cleanup;
+	for (waited_secs = 0; waited_secs < WAIT_TIMEOUT_SECS; waited_secs++) {
+		if (skel->bss->twq_done)
+			break;
+		sleep(1);
+	}
+	if (!ASSERT_TRUE(skel->bss->twq_done, "twq_done in cgroup"))
+		goto cleanup;
+	if (!ASSERT_EQ(skel->bss->callback_cgroup_id, cg_id,
+		       "callback_cgroup_id in cgroup"))
+		goto cleanup;
+
+	/* Run bpf_thread_wq without cgroup attachment (cgroup_id = 0). */
+	LIBBPF_OPTS_RESET(topts);
+	skel->bss->test_key = 1;
+	skel->bss->target_cgroup_id = 0;
+	skel->bss->callback_cgroup_id = 0;
+	skel->bss->twq_done = 0;
+	if (!ASSERT_OK(bpf_prog_test_run_opts(prog_fd, &topts),
+		       "bpf_prog_test_run_opts without cgroup"))
+		goto cleanup;
+	if (!ASSERT_OK(topts.retval, "retval without cgroup"))
+		goto cleanup;
+	for (waited_secs = 0; waited_secs < WAIT_TIMEOUT_SECS; waited_secs++) {
+		if (skel->bss->twq_done)
+			break;
+		sleep(1);
+	}
+	if (!ASSERT_TRUE(skel->bss->twq_done, "twq_done without cgroup"))
+		goto cleanup;
+	if (!ASSERT_NEQ(skel->bss->callback_cgroup_id, cg_id,
+			"callback_cgroup_id without cgroup"))
+		goto cleanup;
+
+cleanup:
+	if (skel) {
+		thread_wq_cgroup__destroy(skel);
+		/* Wait thread_wq kthread quit. */
+		sleep(2);
+	}
+	if (cg_fd >= 0)
+		close(cg_fd);
+	cleanup_cgroup_environment();
+}
diff --git a/tools/testing/selftests/bpf/progs/thread_wq_cgroup.c b/tools/testing/selftests/bpf/progs/thread_wq_cgroup.c
new file mode 100644
index 000000000000..c70a37f55397
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/thread_wq_cgroup.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2026 */
+
+#include "bpf_experimental.h"
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+
+char _license[] SEC("license") = "GPL";
+
+struct elem {
+	struct bpf_thread_wq twq;
+};
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(max_entries, 2);
+	__type(key, int);
+	__type(value, struct elem);
+} map_arr SEC(".maps");
+
+__u64 target_cgroup_id;
+__u64 callback_cgroup_id;
+int twq_done;
+int test_key;
+
+static int twq_callback(void *map, int *key, void *value)
+{
+	callback_cgroup_id = bpf_get_current_cgroup_id();
+	twq_done = 1;
+	return 0;
+}
+
+SEC("syscall")
+int start_thread_wq(void *ctx)
+{
+	struct elem *val;
+	int key = test_key;
+	int ret;
+
+	val = bpf_map_lookup_elem(&map_arr, &key);
+	if (!val)
+		return -1;
+
+	ret = bpf_thread_wq_init(&val->twq, &map_arr, target_cgroup_id, 0);
+	if (ret)
+		goto out;
+
+	ret = bpf_thread_wq_set_callback(&val->twq, twq_callback, 0);
+	if (ret)
+		goto out;
+
+	ret = bpf_thread_wq_start(&val->twq, 0);
+
+out:
+	return ret;
+}
-- 
2.53.0