Re: [PATCH RFC 4/7] selftests/sched: Add basic SCHED_DEADLINE functionality tests

[Gabriele Monaco <gmonaco@redhat.com>]

Hello,

On Fri, 2026-03-06 at 17:10 +0100, Juri Lelli wrote:
> Add initial test coverage for SCHED_DEADLINE scheduler functionality.
> This patch introduces two fundamental tests that validate core
> SCHED_DEADLINE behavior using the test framework and utility library.
> 
> The basic_scheduling test creates a cpuhog process with SCHED_DEADLINE
> policy and verifies the scheduling policy is correctly set to policy 6
> (SCHED_DEADLINE). It confirms the task executes successfully for the
> specified duration using reasonable parameters with 30ms runtime, 100ms
> deadline, and 100ms period. This validates the fundamental operation of
> setting SCHED_DEADLINE policy and running deadline-scheduled tasks.
> 
> The parameter_validation test ensures the kernel properly validates
> SCHED_DEADLINE parameters. It tests that invalid parameter combinations
> such as runtime greater than deadline are correctly rejected with
> EINVAL, while valid parameter configurations are accepted. This confirms
> the kernel's parameter validation logic is working correctly and
> prevents misconfigured deadline tasks from being scheduled.
> 
> Both tests use the dl_util library for SCHED_DEADLINE operations and
> follow the framework pattern with automatic registration via
> REGISTER_DL_TEST(). The tests pass cleanly in VM environments with 2
> tests passing, 0 skipped, and 0 failed.
> 
> Assisted-by: Claude Code: claude-sonnet-4-5@20250929
> Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
> ---
...
>  
> +# Test files
> +$(OUTPUT)/basic.o: basic.c dl_test.h dl_util.h | $(OUTPUT_DIR)
> +	$(CC) $(CFLAGS) -c $< -o $@
> +

This seems a constant in all tests, what about just having make do the trick:

  $(OUTPUT)/%.o: %.c dl_test.h dl_util.h | $(OUTPUT_DIR)
  	$(CC) $(CFLAGS) -c $< -o $@

The rest looks neat.

Thanks,
Gabriele

>  $(OUTPUT_DIR):
>  	mkdir -p $@
>  
> diff --git a/tools/testing/selftests/sched/deadline/basic.c
> b/tools/testing/selftests/sched/deadline/basic.c
> new file mode 100644
> index 0000000000000..f1c4e8c751b61
> --- /dev/null
> +++ b/tools/testing/selftests/sched/deadline/basic.c
> @@ -0,0 +1,127 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Basic SCHED_DEADLINE functionality tests
> + *
> + * Validates fundamental SCHED_DEADLINE scheduler operations including
> + * policy setup, parameter validation, and basic task execution.
> + */
> +
> +#define _GNU_SOURCE
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <unistd.h>
> +#include <sys/types.h>
> +#include <sys/wait.h>
> +#include <errno.h>
> +#include <sched.h>
> +#include "dl_test.h"
> +#include "dl_util.h"
> +
> +/*
> + * Test: Basic SCHED_DEADLINE scheduling
> + *
> + * Verifies that a task can be successfully scheduled with SCHED_DEADLINE
> + * policy and executes correctly.
> + */
> +static enum dl_test_status test_basic_scheduling_run(void *ctx)
> +{
> +	pid_t pid;
> +	int policy;
> +	int status;
> +	uint64_t runtime_ns, deadline_ns, period_ns;
> +
> +	/* Use reasonable deadline parameters: 30ms/100ms/100ms */
> +	runtime_ns = dl_ms_to_ns(30);
> +	deadline_ns = dl_ms_to_ns(100);
> +	period_ns = dl_ms_to_ns(100);
> +
> +	/* Create a cpuhog process with SCHED_DEADLINE */
> +	pid = dl_create_cpuhog(runtime_ns, deadline_ns, period_ns, 2);
> +	DL_FAIL_IF(pid < 0, "Failed to create cpuhog process: %s",
> +		   strerror(errno));
> +
> +	/* Process is now running with SCHED_DEADLINE set */
> +	printf("  Created cpuhog with SCHED_DEADLINE (PID %d)\n", pid);
> +
> +	/* Verify it's using SCHED_DEADLINE (policy 6) */
> +	policy = dl_get_policy(pid);
> +	DL_FAIL_IF(policy < 0, "Failed to read scheduling policy");
> +	DL_EQ(policy, SCHED_DEADLINE);
> +
> +	/* Alternative check using helper */
> +	DL_ASSERT(dl_is_deadline_task(pid));
> +
> +	printf("  cpuhog running with SCHED_DEADLINE (PID %d)\n", pid);
> +
> +	/* Wait for cpuhog to complete (2 seconds) */
> +	if (waitpid(pid, &status, 0) < 0) {
> +		dl_cleanup_cpuhog(pid);
> +		DL_FAIL("waitpid failed: %s", strerror(errno));
> +	}
> +
> +	/* Verify it exited successfully */
> +	DL_FAIL_IF(!WIFEXITED(status), "Process did not exit normally");
> +	DL_EQ(WEXITSTATUS(status), 0);
> +
> +	printf("  cpuhog completed successfully\n");
> +
> +	return DL_TEST_PASS;
> +}
> +
> +static struct dl_test test_basic_scheduling = {
> +	.name = "basic_scheduling",
> +	.description = "Verify basic SCHED_DEADLINE policy setup and
> execution",
> +	.run = test_basic_scheduling_run,
> +};
> +REGISTER_DL_TEST(&test_basic_scheduling);
> +
> +/*
> + * Test: SCHED_DEADLINE parameter validation
> + *
> + * Verifies that the kernel correctly validates deadline parameters,
> + * rejecting invalid configurations and accepting valid ones.
> + */
> +static enum dl_test_status test_parameter_validation_run(void *ctx)
> +{
> +	int ret;
> +	uint64_t runtime_ns, deadline_ns, period_ns;
> +
> +	printf("  Testing invalid parameters (runtime > deadline)...\n");
> +
> +	/* Invalid: runtime (200ms) > deadline (100ms) */
> +	runtime_ns = dl_ms_to_ns(200);
> +	deadline_ns = dl_ms_to_ns(100);
> +	period_ns = dl_ms_to_ns(100);
> +
> +	ret = dl_set_sched_attr(0, runtime_ns, deadline_ns, period_ns);
> +	DL_FAIL_IF(ret == 0, "Invalid parameters were accepted (runtime >
> deadline)");
> +	DL_FAIL_IF(errno != EINVAL, "Expected EINVAL, got %s",
> strerror(errno));
> +
> +	printf("  Invalid parameters correctly rejected with EINVAL\n");
> +
> +	printf("  Testing valid parameters...\n");
> +
> +	/* Valid: runtime (30ms) <= deadline (100ms) <= period (100ms) */
> +	runtime_ns = dl_ms_to_ns(30);
> +	deadline_ns = dl_ms_to_ns(100);
> +	period_ns = dl_ms_to_ns(100);
> +
> +	ret = dl_set_sched_attr(0, runtime_ns, deadline_ns, period_ns);
> +	DL_FAIL_IF(ret < 0, "Valid parameters were rejected: %s",
> strerror(errno));
> +
> +	printf("  Valid parameters correctly accepted\n");
> +
> +	/* Reset to normal scheduling using sched_setscheduler */
> +	struct sched_param param = { .sched_priority = 0 };
> +
> +	sched_setscheduler(0, SCHED_OTHER, &param);
> +
> +	return DL_TEST_PASS;
> +}
> +
> +static struct dl_test test_parameter_validation = {
> +	.name = "parameter_validation",
> +	.description = "Verify SCHED_DEADLINE parameter validation
> (accept/reject)",
> +	.run = test_parameter_validation_run,
> +};
> +REGISTER_DL_TEST(&test_parameter_validation);