1 files changed, 224 insertions, 0 deletions
diff --git a/tools/testing/selftests/sched_ext/peek_dsq.c b/tools/testing/selftests/sched_ext/peek_dsq.c
new file mode 100644
index 000000000000..a717384a3224
--- /dev/null
+++ b/tools/testing/selftests/sched_ext/peek_dsq.c
@@ -0,0 +1,224 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Test for DSQ operations including create, destroy, and peek operations.
+ *
+ * Copyright (c) 2025 Meta Platforms, Inc. and affiliates.
+ * Copyright (c) 2025 Ryan Newton <ryan.newton@alum.mit.edu>
+ */
+#include <bpf/bpf.h>
+#include <scx/common.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <pthread.h>
+#include <string.h>
+#include <sched.h>
+#include "peek_dsq.bpf.skel.h"
+#include "scx_test.h"
+
+#define NUM_WORKERS 4
+
+static bool workload_running = true;
+static pthread_t workload_threads[NUM_WORKERS];
+
+/**
+ * Background workload thread that sleeps and wakes rapidly to exercise
+ * the scheduler's enqueue operations and ensure DSQ operations get tested.
+ */
+static void *workload_thread_fn(void *arg)
+{
+	while (workload_running) {
+		/* Sleep for a very short time to trigger scheduler activity */
+		usleep(1000); /* 1ms sleep */
+		/* Yield to ensure we go through the scheduler */
+		sched_yield();
+	}
+	return NULL;
+}
+
+static enum scx_test_status setup(void **ctx)
+{
+	struct peek_dsq *skel;
+
+	skel = peek_dsq__open();
+	SCX_FAIL_IF(!skel, "Failed to open");
+	SCX_ENUM_INIT(skel);
+	SCX_FAIL_IF(peek_dsq__load(skel), "Failed to load skel");
+
+	*ctx = skel;
+
+	return SCX_TEST_PASS;
+}
+
+static int print_observed_pids(struct bpf_map *map, int max_samples, const char *dsq_name)
+{
+	long count = 0;
+
+	printf("Observed %s DSQ peek pids:\n", dsq_name);
+	for (int i = 0; i < max_samples; i++) {
+		long pid;
+		int err;
+
+		err = bpf_map_lookup_elem(bpf_map__fd(map), &i, &pid);
+		if (err == 0) {
+			if (pid == 0) {
+				printf("  Sample %d: NULL peek\n", i);
+			} else if (pid > 0) {
+				printf("  Sample %d: pid %ld\n", i, pid);
+				count++;
+			}
+		} else {
+			printf("  Sample %d: error reading pid (err=%d)\n", i, err);
+		}
+	}
+	printf("Observed ~%ld pids in the %s DSQ(s)\n", count, dsq_name);
+	return count;
+}
+
+static enum scx_test_status run(void *ctx)
+{
+	struct peek_dsq *skel = ctx;
+	bool failed = false;
+	int seconds = 3;
+	int err;
+
+	/* Enable the scheduler to test DSQ operations */
+	printf("Enabling scheduler to test DSQ insert operations...\n");
+
+	struct bpf_link *link =
+		bpf_map__attach_struct_ops(skel->maps.peek_dsq_ops);
+
+	if (!link) {
+		SCX_ERR("Failed to attach struct_ops");
+		return SCX_TEST_FAIL;
+	}
+
+	printf("Starting %d background workload threads...\n", NUM_WORKERS);
+	workload_running = true;
+	for (int i = 0; i < NUM_WORKERS; i++) {
+		err = pthread_create(&workload_threads[i], NULL, workload_thread_fn, NULL);
+		if (err) {
+			SCX_ERR("Failed to create workload thread %d: %s", i, strerror(err));
+			/* Stop already created threads */
+			workload_running = false;
+			for (int j = 0; j < i; j++)
+				pthread_join(workload_threads[j], NULL);
+			bpf_link__destroy(link);
+			return SCX_TEST_FAIL;
+		}
+	}
+
+	printf("Waiting for enqueue events.\n");
+	sleep(seconds);
+	while (skel->data->enqueue_count <= 0) {
+		printf(".");
+		fflush(stdout);
+		sleep(1);
+		seconds++;
+		if (seconds >= 30) {
+			printf("\n\u2717 Timeout waiting for enqueue events\n");
+			/* Stop workload threads and cleanup */
+			workload_running = false;
+			for (int i = 0; i < NUM_WORKERS; i++)
+				pthread_join(workload_threads[i], NULL);
+			bpf_link__destroy(link);
+			return SCX_TEST_FAIL;
+		}
+	}
+
+	workload_running = false;
+	for (int i = 0; i < NUM_WORKERS; i++) {
+		err = pthread_join(workload_threads[i], NULL);
+		if (err) {
+			SCX_ERR("Failed to join workload thread %d: %s", i, strerror(err));
+			bpf_link__destroy(link);
+			return SCX_TEST_FAIL;
+		}
+	}
+	printf("Background workload threads stopped.\n");
+
+	SCX_EQ(skel->data->uei.kind, EXIT_KIND(SCX_EXIT_NONE));
+
+	/* Detach the scheduler */
+	bpf_link__destroy(link);
+
+	printf("Enqueue/dispatch count over %d seconds: %d / %d\n", seconds,
+		skel->data->enqueue_count, skel->data->dispatch_count);
+	printf("Debug: ksym_exists=%d\n",
+	       skel->bss->debug_ksym_exists);
+
+	/* Check DSQ insert result */
+	printf("DSQ insert test done on cpu: %d\n", skel->data->insert_test_cpu);
+	if (skel->data->insert_test_cpu != -1)
+		printf("\u2713 DSQ insert succeeded !\n");
+	else {
+		printf("\u2717 DSQ insert failed or not attempted\n");
+		failed = true;
+	}
+
+	/* Check DSQ peek results */
+	printf("  DSQ peek result 1 (before insert): %d\n",
+	       skel->data->dsq_peek_result1);
+	if (skel->data->dsq_peek_result1 == 0)
+		printf("\u2713 DSQ peek verification success: peek returned NULL!\n");
+	else {
+		printf("\u2717 DSQ peek verification failed\n");
+		failed = true;
+	}
+
+	printf("  DSQ peek result 2 (after insert): %ld\n",
+	       skel->data->dsq_peek_result2);
+	printf("  DSQ peek result 2, expected: %ld\n",
+	       skel->data->dsq_peek_result2_expected);
+	if (skel->data->dsq_peek_result2 ==
+	    skel->data->dsq_peek_result2_expected)
+		printf("\u2713 DSQ peek verification success: peek returned the inserted task!\n");
+	else {
+		printf("\u2717 DSQ peek verification failed\n");
+		failed = true;
+	}
+
+	printf("  Inserted test task -> pid: %ld\n", skel->data->dsq_inserted_pid);
+	printf("  DSQ peek result 2 -> pid: %ld\n", skel->data->dsq_peek_result2_pid);
+
+	int pid_count;
+
+	pid_count = print_observed_pids(skel->maps.peek_results,
+					skel->data->max_samples, "DSQ pool");
+	printf("Total non-null peek observations: %ld out of %ld\n",
+	       skel->data->successful_peeks, skel->data->total_peek_attempts);
+
+	if (skel->bss->debug_ksym_exists && pid_count == 0) {
+		printf("\u2717 DSQ pool test failed: no successful peeks in native mode\n");
+		failed = true;
+	}
+	if (skel->bss->debug_ksym_exists && pid_count > 0)
+		printf("\u2713 DSQ pool test success: observed successful peeks in native mode\n");
+
+	if (failed)
+		return SCX_TEST_FAIL;
+	else
+		return SCX_TEST_PASS;
+}
+
+static void cleanup(void *ctx)
+{
+	struct peek_dsq *skel = ctx;
+
+	if (workload_running) {
+		workload_running = false;
+		for (int i = 0; i < NUM_WORKERS; i++)
+			pthread_join(workload_threads[i], NULL);
+	}
+
+	peek_dsq__destroy(skel);
+}
+
+struct scx_test peek_dsq = {
+	.name = "peek_dsq",
+	.description =
+		"Test DSQ create/destroy operations and future peek functionality",
+	.setup = setup,
+	.run = run,
+	.cleanup = cleanup,
+};
+REGISTER_SCX_TEST(&peek_dsq)