tests/kernel/sched/schedule_api/src/test_priority_scheduling.c

/*
 * Copyright (c) 2017 Intel Corporation
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <ztest.h>
#include "test_sched.h"

/* nrf 51 has lower ram, so creating less number of threads */
#if CONFIG_SRAM_SIZE <= 24
	#define NUM_THREAD 2
#elif (CONFIG_SRAM_SIZE <= 32) \
	|| defined(CONFIG_SOC_EMSK_EM7D)
	#define NUM_THREAD 3
#else
	#define NUM_THREAD 10
#endif
#define ITRERATION_COUNT 5
#define BASE_PRIORITY 1

BUILD_ASSERT(NUM_THREAD <= MAX_NUM_THREAD);

/* Semaphore on which Ztest thread wait */
static K_SEM_DEFINE(sema2, 0, NUM_THREAD);

/* Semaphore on which application threads wait */
static K_SEM_DEFINE(sema3, 0, NUM_THREAD);

static int thread_idx;
static struct k_thread t[NUM_THREAD];

/* Application thread */
static void thread_tslice(void *p1, void *p2, void *p3)
{
	int idx = POINTER_TO_INT(p1);

	/* Print New line for last thread */
	int thread_parameter = (idx == (NUM_THREAD - 1)) ? '\n' :
			       (idx + 'A');

	while (1) {
		/* Printing alphabet corresponding to thread */
		TC_PRINT("%c", thread_parameter);
		/* Testing if threads are executed as per priority */
		zassert_true((idx == thread_idx), NULL);
		thread_idx = (thread_idx + 1) % (NUM_THREAD);

		/* Release CPU and give chance to Ztest thread to run */
		k_sem_give(&sema2);
		/* Wait for release of semaphore from Ztest thread */
		k_sem_take(&sema3, K_FOREVER);
	}

}

/* test cases */

/**
 * @brief Check the behavior of preemptive threads with different priorities
 *
 * @details Create multiple threads of different priorities - all are preemptive,
 * current thread is also made preemptive. Check how the threads get chance to
 * execute based on their priorities
 *
 * @ingroup kernel_sched_tests
 */
void test_priority_scheduling(void)
{
	k_tid_t tid[NUM_THREAD];
	int old_prio = k_thread_priority_get(k_current_get());
	int count = 0;

	/* update priority for current thread */
	k_thread_priority_set(k_current_get(),
			      K_PRIO_PREEMPT(BASE_PRIORITY - 1));

	/* Create Threads with different Priority */
	for (int i = 0; i < NUM_THREAD; i++) {
		tid[i] = k_thread_create(&t[i], tstacks[i], STACK_SIZE,
					 thread_tslice, INT_TO_POINTER(i), NULL, NULL,
					 K_PRIO_PREEMPT(BASE_PRIORITY + i), 0,
					 K_NO_WAIT);
	}

	while (count < ITRERATION_COUNT) {

		/* Wait for each thread to complete */
		for (int i = 0; i < NUM_THREAD; i++) {
			k_sem_take(&sema2, K_FOREVER);
		}
		/* Delay to give chance to last thread to run */
		k_sleep(K_MSEC(1));

		/* Giving Chance to other threads to run */
		for (int i = 0; i < NUM_THREAD; i++) {
			k_sem_give(&sema3);
		}
		count++;
	}


	/* test case teardown */
	for (int i = 0; i < NUM_THREAD; i++) {
		k_thread_abort(tid[i]);
	}
	/* Set priority of Main thread to its old value */
	k_thread_priority_set(k_current_get(), old_prio);
}