1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * ops.dequeue() of this scheduler iterates the user DSQ it consumes
4 * tasks from with bpf_iter_scx_dsq, which takes the DSQ lock.
5 * On a kernel that still runs ops.dequeue() with that lock held, the
6 * iteration self-deadlocks the CPU - this test wedges the system on
7 * unfixed kernels instead of failing cleanly.
8 *
9 * Copyright (c) 2026 fangqiurong <fangqiurong@kylinos.cn>
10 */
11
12 #include <scx/common.bpf.h>
13
14 char _license[] SEC("license") = "GPL";
15
16 UEI_DEFINE(uei);
17
18 #define TEST_DSQ_ID 1000
19
20 u64 dq_count;
21
BPF_STRUCT_OPS_SLEEPABLE(dequeue_iter_init)22 s32 BPF_STRUCT_OPS_SLEEPABLE(dequeue_iter_init)
23 {
24 return scx_bpf_create_dsq(TEST_DSQ_ID, -1);
25 }
26
BPF_STRUCT_OPS(dequeue_iter_select_cpu,struct task_struct * p,s32 prev_cpu,u64 wake_flags)27 s32 BPF_STRUCT_OPS(dequeue_iter_select_cpu, struct task_struct *p,
28 s32 prev_cpu, u64 wake_flags)
29 {
30 return prev_cpu;
31 }
32
BPF_STRUCT_OPS(dequeue_iter_enqueue,struct task_struct * p,u64 enq_flags)33 void BPF_STRUCT_OPS(dequeue_iter_enqueue, struct task_struct *p, u64 enq_flags)
34 {
35 scx_bpf_dsq_insert(p, TEST_DSQ_ID, SCX_SLICE_DFL, enq_flags);
36 }
37
BPF_STRUCT_OPS(dequeue_iter_dispatch,s32 cpu,struct task_struct * task)38 void BPF_STRUCT_OPS(dequeue_iter_dispatch, s32 cpu, struct task_struct *task)
39 {
40 scx_bpf_dsq_move_to_local(TEST_DSQ_ID, 0);
41 }
42
BPF_STRUCT_OPS(dequeue_iter_dequeue,struct task_struct * p,u64 deq_flags)43 void BPF_STRUCT_OPS(dequeue_iter_dequeue, struct task_struct *p, u64 deq_flags)
44 {
45 struct bpf_iter_scx_dsq it;
46 struct task_struct *t;
47
48 if (!bpf_iter_scx_dsq_new(&it, TEST_DSQ_ID, 0)) {
49 while ((t = bpf_iter_scx_dsq_next(&it)))
50 ;
51 }
52 bpf_iter_scx_dsq_destroy(&it);
53
54 __sync_fetch_and_add(&dq_count, 1);
55 }
56
BPF_STRUCT_OPS(dequeue_iter_exit,struct scx_exit_info * ei)57 void BPF_STRUCT_OPS(dequeue_iter_exit, struct scx_exit_info *ei)
58 {
59 UEI_RECORD(uei, ei);
60 scx_bpf_destroy_dsq(TEST_DSQ_ID);
61 }
62
63 SEC(".struct_ops.link")
64 struct sched_ext_ops dequeue_iter_ops = {
65 .init = (void *)dequeue_iter_init,
66 .select_cpu = (void *)dequeue_iter_select_cpu,
67 .enqueue = (void *)dequeue_iter_enqueue,
68 .dispatch = (void *)dequeue_iter_dispatch,
69 .dequeue = (void *)dequeue_iter_dequeue,
70 .exit = (void *)dequeue_iter_exit,
71 .timeout_ms = 1000U,
72 .name = "dequeue_iter",
73 };
74