1 files changed, 143 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/progs/res_spin_lock.c b/tools/testing/selftests/bpf/progs/res_spin_lock.c
new file mode 100644
index 000000000000..b33385dfbd35
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/res_spin_lock.c
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024-2025 Meta Platforms, Inc. and affiliates. */
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+
+#define EDEADLK 35
+#define ETIMEDOUT 110
+
+struct arr_elem {
+	struct bpf_res_spin_lock lock;
+};
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(max_entries, 64);
+	__type(key, int);
+	__type(value, struct arr_elem);
+} arrmap SEC(".maps");
+
+struct bpf_res_spin_lock lockA __hidden SEC(".data.A");
+struct bpf_res_spin_lock lockB __hidden SEC(".data.B");
+
+SEC("tc")
+int res_spin_lock_test(struct __sk_buff *ctx)
+{
+	struct arr_elem *elem1, *elem2;
+	int r;
+
+	elem1 = bpf_map_lookup_elem(&arrmap, &(int){0});
+	if (!elem1)
+		return -1;
+	elem2 = bpf_map_lookup_elem(&arrmap, &(int){0});
+	if (!elem2)
+		return -1;
+
+	r = bpf_res_spin_lock(&elem1->lock);
+	if (r)
+		return r;
+	if (!bpf_res_spin_lock(&elem2->lock)) {
+		bpf_res_spin_unlock(&elem2->lock);
+		bpf_res_spin_unlock(&elem1->lock);
+		return -1;
+	}
+	bpf_res_spin_unlock(&elem1->lock);
+	return 0;
+}
+
+SEC("tc")
+int res_spin_lock_test_AB(struct __sk_buff *ctx)
+{
+	int r;
+
+	r = bpf_res_spin_lock(&lockA);
+	if (r)
+		return !r;
+	/* Only unlock if we took the lock. */
+	if (!bpf_res_spin_lock(&lockB))
+		bpf_res_spin_unlock(&lockB);
+	bpf_res_spin_unlock(&lockA);
+	return 0;
+}
+
+int err;
+
+SEC("tc")
+int res_spin_lock_test_BA(struct __sk_buff *ctx)
+{
+	int r;
+
+	r = bpf_res_spin_lock(&lockB);
+	if (r)
+		return !r;
+	if (!bpf_res_spin_lock(&lockA))
+		bpf_res_spin_unlock(&lockA);
+	else
+		err = -EDEADLK;
+	bpf_res_spin_unlock(&lockB);
+	return err ?: 0;
+}
+
+SEC("tc")
+int res_spin_lock_test_held_lock_max(struct __sk_buff *ctx)
+{
+	struct bpf_res_spin_lock *locks[48] = {};
+	struct arr_elem *e;
+	u64 time_beg, time;
+	int ret = 0, i;
+
+	_Static_assert(ARRAY_SIZE(((struct rqspinlock_held){}).locks) == 31,
+		       "RES_NR_HELD assumed to be 31");
+
+	for (i = 0; i < 34; i++) {
+		int key = i;
+
+		/* We cannot pass in i as it will get spilled/filled by the compiler and
+		 * loses bounds in verifier state.
+		 */
+		e = bpf_map_lookup_elem(&arrmap, &key);
+		if (!e)
+			return 1;
+		locks[i] = &e->lock;
+	}
+
+	for (; i < 48; i++) {
+		int key = i - 2;
+
+		/* We cannot pass in i as it will get spilled/filled by the compiler and
+		 * loses bounds in verifier state.
+		 */
+		e = bpf_map_lookup_elem(&arrmap, &key);
+		if (!e)
+			return 1;
+		locks[i] = &e->lock;
+	}
+
+	time_beg = bpf_ktime_get_ns();
+	for (i = 0; i < 34; i++) {
+		if (bpf_res_spin_lock(locks[i]))
+			goto end;
+	}
+
+	/* Trigger AA, after exhausting entries in the held lock table. This
+	 * time, only the timeout can save us, as AA detection won't succeed.
+	 */
+	if (!bpf_res_spin_lock(locks[34])) {
+		bpf_res_spin_unlock(locks[34]);
+		ret = 1;
+		goto end;
+	}
+
+end:
+	for (i = i - 1; i >= 0; i--)
+		bpf_res_spin_unlock(locks[i]);
+	time = bpf_ktime_get_ns() - time_beg;
+	/* Time spent should be easily above our limit (1/4 s), since AA
+	 * detection won't be expedited due to lack of held lock entry.
+	 */
+	return ret ?: (time > 1000000000 / 4 ? 0 : 1);
+}
+
+char _license[] SEC("license") = "GPL";