1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * A scheduler that validates the behavior of direct dispatching with a default
4 * select_cpu implementation, and with the SCX_OPS_ENQ_DFL_NO_DISPATCH ops flag
5 * specified.
6 *
7 * Copyright (c) 2023 Meta Platforms, Inc. and affiliates.
8 * Copyright (c) 2023 David Vernet <dvernet@meta.com>
9 * Copyright (c) 2023 Tejun Heo <tj@kernel.org>
10 */
11
12 #include <scx/common.bpf.h>
13
14 char _license[] SEC("license") = "GPL";
15
16 bool saw_local = false;
17
18 /* Per-task scheduling context */
19 struct task_ctx {
20 bool force_local; /* CPU changed by ops.select_cpu() */
21 };
22
23 struct {
24 __uint(type, BPF_MAP_TYPE_TASK_STORAGE);
25 __uint(map_flags, BPF_F_NO_PREALLOC);
26 __type(key, int);
27 __type(value, struct task_ctx);
28 } task_ctx_stor SEC(".maps");
29
30 /* Manually specify the signature until the kfunc is added to the scx repo. */
31 s32 scx_bpf_select_cpu_dfl(struct task_struct *p, s32 prev_cpu, u64 wake_flags,
32 bool *found) __ksym;
33
34 s32 BPF_STRUCT_OPS(select_cpu_dfl_nodispatch_select_cpu, struct task_struct *p,
35 s32 prev_cpu, u64 wake_flags)
36 {
37 struct task_ctx *tctx;
38 s32 cpu;
39
40 tctx = bpf_task_storage_get(&task_ctx_stor, p, 0, 0);
41 if (!tctx) {
42 scx_bpf_error("task_ctx lookup failed");
43 return -ESRCH;
44 }
45
46 cpu = scx_bpf_select_cpu_dfl(p, prev_cpu, wake_flags,
47 &tctx->force_local);
48
49 return cpu;
50 }
51
52 void BPF_STRUCT_OPS(select_cpu_dfl_nodispatch_enqueue, struct task_struct *p,
53 u64 enq_flags)
54 {
55 u64 dsq_id = SCX_DSQ_GLOBAL;
56 struct task_ctx *tctx;
57
58 tctx = bpf_task_storage_get(&task_ctx_stor, p, 0, 0);
59 if (!tctx) {
60 scx_bpf_error("task_ctx lookup failed");
61 return;
62 }
63
64 if (tctx->force_local) {
65 dsq_id = SCX_DSQ_LOCAL;
66 tctx->force_local = false;
67 saw_local = true;
68 }
69
70 scx_bpf_dispatch(p, dsq_id, SCX_SLICE_DFL, enq_flags);
71 }
72
73 s32 BPF_STRUCT_OPS(select_cpu_dfl_nodispatch_init_task,
74 struct task_struct *p, struct scx_init_task_args *args)
75 {
76 if (bpf_task_storage_get(&task_ctx_stor, p, 0,
77 BPF_LOCAL_STORAGE_GET_F_CREATE))
78 return 0;
79 else
80 return -ENOMEM;
81 }
82
83 SEC(".struct_ops.link")
84 struct sched_ext_ops select_cpu_dfl_nodispatch_ops = {
85 .select_cpu = (void *) select_cpu_dfl_nodispatch_select_cpu,
86 .enqueue = (void *) select_cpu_dfl_nodispatch_enqueue,
87 .init_task = (void *) select_cpu_dfl_nodispatch_init_task,
88 .name = "select_cpu_dfl_nodispatch",
89 };
90
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