1 files changed, 73 insertions, 0 deletions
diff --git a/tools/testing/selftests/sched_ext/dequeue_iter.bpf.c b/tools/testing/selftests/sched_ext/dequeue_iter.bpf.c
new file mode 100644
index 000000000000..76c2c71a90b6
--- /dev/null
+++ b/tools/testing/selftests/sched_ext/dequeue_iter.bpf.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ops.dequeue() of this scheduler iterates the user DSQ it consumes
+ * tasks from with bpf_iter_scx_dsq, which takes the DSQ lock.
+ * On a kernel that still runs ops.dequeue() with that lock held, the
+ * iteration self-deadlocks the CPU - this test wedges the system on
+ * unfixed kernels instead of failing cleanly.
+ *
+ * Copyright (c) 2026 fangqiurong <fangqiurong@kylinos.cn>
+ */
+
+#include <scx/common.bpf.h>
+
+char _license[] SEC("license") = "GPL";
+
+UEI_DEFINE(uei);
+
+#define TEST_DSQ_ID 1000
+
+u64 dq_count;
+
+s32 BPF_STRUCT_OPS_SLEEPABLE(dequeue_iter_init)
+{
+	return scx_bpf_create_dsq(TEST_DSQ_ID, -1);
+}
+
+s32 BPF_STRUCT_OPS(dequeue_iter_select_cpu, struct task_struct *p,
+		   s32 prev_cpu, u64 wake_flags)
+{
+	return prev_cpu;
+}
+
+void BPF_STRUCT_OPS(dequeue_iter_enqueue, struct task_struct *p, u64 enq_flags)
+{
+	scx_bpf_dsq_insert(p, TEST_DSQ_ID, SCX_SLICE_DFL, enq_flags);
+}
+
+void BPF_STRUCT_OPS(dequeue_iter_dispatch, s32 cpu, struct task_struct *task)
+{
+	scx_bpf_dsq_move_to_local(TEST_DSQ_ID, 0);
+}
+
+void BPF_STRUCT_OPS(dequeue_iter_dequeue, struct task_struct *p, u64 deq_flags)
+{
+	struct bpf_iter_scx_dsq it;
+	struct task_struct *t;
+
+	if (!bpf_iter_scx_dsq_new(&it, TEST_DSQ_ID, 0)) {
+		while ((t = bpf_iter_scx_dsq_next(&it)))
+			;
+	}
+	bpf_iter_scx_dsq_destroy(&it);
+
+	__sync_fetch_and_add(&dq_count, 1);
+}
+
+void BPF_STRUCT_OPS(dequeue_iter_exit, struct scx_exit_info *ei)
+{
+	UEI_RECORD(uei, ei);
+	scx_bpf_destroy_dsq(TEST_DSQ_ID);
+}
+
+SEC(".struct_ops.link")
+struct sched_ext_ops dequeue_iter_ops = {
+	.init			= (void *)dequeue_iter_init,
+	.select_cpu		= (void *)dequeue_iter_select_cpu,
+	.enqueue		= (void *)dequeue_iter_enqueue,
+	.dispatch		= (void *)dequeue_iter_dispatch,
+	.dequeue		= (void *)dequeue_iter_dequeue,
+	.exit			= (void *)dequeue_iter_exit,
+	.timeout_ms		= 1000U,
+	.name			= "dequeue_iter",
+};