sched_ext: Add selftests

Add basic selftests.

Signed-off-by: David Vernet <dvernet@meta.com>
Acked-by: Tejun Heo <tj@kernel.org>

1 files changed, 40 insertions, 0 deletions

diff --git a/tools/testing/selftests/sched_ext/select_cpu_dfl.bpf.c b/tools/testing/selftests/sched_ext/select_cpu_dfl.bpf.c
new file mode 100644
index 000000000000..2ed2991afafe
--- /dev/null
+++ b/tools/testing/selftests/sched_ext/select_cpu_dfl.bpf.c
@@ -0,0 +1,40 @@
+/* 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";
+
+bool saw_local = false;
+
+static bool task_is_test(const struct task_struct *p)
+{
+	return !bpf_strncmp(p->comm, 9, "select_cpu");
+}
+
+void BPF_STRUCT_OPS(select_cpu_dfl_enqueue, struct task_struct *p,
+		    u64 enq_flags)
+{
+	const struct cpumask *idle_mask = scx_bpf_get_idle_cpumask();
+
+	if (task_is_test(p) &&
+	    bpf_cpumask_test_cpu(scx_bpf_task_cpu(p), idle_mask)) {
+		saw_local = true;
+	}
+	scx_bpf_put_idle_cpumask(idle_mask);
+
+	scx_bpf_dispatch(p, SCX_DSQ_GLOBAL, SCX_SLICE_DFL, enq_flags);
+}
+
+SEC(".struct_ops.link")
+struct sched_ext_ops select_cpu_dfl_ops = {
+	.enqueue		= select_cpu_dfl_enqueue,
+	.name			= "select_cpu_dfl",
+};