/* SPDX-License-Identifier: GPL-2.0 */
/*
 * A scheduler that validates the behavior of direct dispatching with a default
 * select_cpu implementation.
 *
 * Copyright (c) 2023 Meta Platforms, Inc. and affiliates.
 * Copyright (c) 2023 David Vernet <dvernet@meta.com>
 * Copyright (c) 2023 Tejun Heo <tj@kernel.org>
 */

#include <scx/common.bpf.h>

char _license[] SEC("license") = "GPL";

s32 BPF_STRUCT_OPS(select_cpu_dispatch_select_cpu, struct task_struct *p,
                   s32 prev_cpu, u64 wake_flags)
{
        u64 dsq_id = SCX_DSQ_LOCAL;
        s32 cpu = prev_cpu;

        if (scx_bpf_test_and_clear_cpu_idle(cpu))
                goto dispatch;

        cpu = scx_bpf_pick_idle_cpu(p->cpus_ptr, 0);
        if (cpu >= 0)
                goto dispatch;

        dsq_id = SCX_DSQ_GLOBAL;
        cpu = prev_cpu;

dispatch:
        scx_bpf_dsq_insert(p, dsq_id, SCX_SLICE_DFL, 0);
        return cpu;
}

SEC(".struct_ops.link")
struct sched_ext_ops select_cpu_dispatch_ops = {
        .select_cpu             = (void *) select_cpu_dispatch_select_cpu,
        .name                   = "select_cpu_dispatch",
        .timeout_ms             = 1000U,
};