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