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
14char _license[] SEC("license") = "GPL";
15
16bool saw_local = false;
17
18/* Per-task scheduling context */
19struct task_ctx {
20	bool	force_local;	/* CPU changed by ops.select_cpu() */
21};
22
23struct {
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. */
31s32 scx_bpf_select_cpu_dfl(struct task_struct *p, s32 prev_cpu, u64 wake_flags,
32			   bool *found) __ksym;
33
34s32 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
52void 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_dsq_insert(p, dsq_id, SCX_SLICE_DFL, enq_flags);
71}
72
73s32 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
83SEC(".struct_ops.link")
84struct 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};