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.
 5 *
 6 * Copyright (c) 2023 Meta Platforms, Inc. and affiliates.
 7 * Copyright (c) 2023 David Vernet <dvernet@meta.com>
 8 * Copyright (c) 2023 Tejun Heo <tj@kernel.org>
 9 */
10
11#include <scx/common.bpf.h>
12
13char _license[] SEC("license") = "GPL";
14
15s32 BPF_STRUCT_OPS(select_cpu_dispatch_select_cpu, struct task_struct *p,
16		   s32 prev_cpu, u64 wake_flags)
17{
18	u64 dsq_id = SCX_DSQ_LOCAL;
19	s32 cpu = prev_cpu;
20
21	if (scx_bpf_test_and_clear_cpu_idle(cpu))
22		goto dispatch;
23
24	cpu = scx_bpf_pick_idle_cpu(p->cpus_ptr, 0);
25	if (cpu >= 0)
26		goto dispatch;
27
28	dsq_id = SCX_DSQ_GLOBAL;
29	cpu = prev_cpu;
30
31dispatch:
32	scx_bpf_dsq_insert(p, dsq_id, SCX_SLICE_DFL, 0);
33	return cpu;
34}
35
36SEC(".struct_ops.link")
37struct sched_ext_ops select_cpu_dispatch_ops = {
38	.select_cpu		= (void *) select_cpu_dispatch_select_cpu,
39	.name			= "select_cpu_dispatch",
40	.timeout_ms		= 1000U,
41};