text: /*
   * Copyright (c) 2017 Intel Corporation
   *
   * SPDX-License-Identifier: Apache-2.0
   */
  
  #include <ztest.h>
  #include "test_sched.h"
  
  #ifdef CONFIG_TIMESLICING
  
  /* 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 BASE_PRIORITY 0
  #define ITRERATION_COUNT 5
  BUILD_ASSERT(NUM_THREAD <= MAX_NUM_THREAD);
  /* slice size in millisecond */
  #define SLICE_SIZE 200
  /* busy for more than one slice */
  #define BUSY_MS (SLICE_SIZE + 20)
  static struct k_thread t[NUM_THREAD];
  
  static K_SEM_DEFINE(sema1, 0, NUM_THREAD);
  /* elapsed_slice taken by last thread */
  static int64_t elapsed_slice;
  
  static int thread_idx;
  
  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');
  
  	int64_t expected_slice_min = k_ticks_to_ms_floor64(k_ms_to_ticks_ceil32(SLICE_SIZE));
  	int64_t expected_slice_max = k_ticks_to_ms_floor64(k_ms_to_ticks_ceil32(SLICE_SIZE) + 1);
  
  	/* Clumsy, but need to handle the precision loss with
  	 * submillisecond ticks.  It's always possible to alias and
  	 * produce a tdelta of "1", no matter how fast ticks are.
  	 */
  	if (expected_slice_max == expected_slice_min) {
  		expected_slice_max = expected_slice_min + 1;
  	}
  
  	while (1) {
  		int64_t tdelta = k_uptime_delta(&elapsed_slice);
  		TC_PRINT("%c", thread_parameter);
  		/* Test Fails if thread exceed allocated time slice or
  		 * Any thread is scheduled out of order.
  		 */
  		zassert_true(((tdelta >= expected_slice_min) &&
  			      (tdelta <= expected_slice_max) &&
  			      (idx == thread_idx)), NULL);
  		thread_idx = (thread_idx + 1) % (NUM_THREAD);
  
  		/* Keep the current thread busy for more than one slice,
  		 * even though, when timeslice used up the next thread
  		 * should be scheduled in.
  		 */
  		spin_for_ms(BUSY_MS);
  		k_sem_give(&sema1);
  	}
  }
  
  /* test cases */
  
  /**
   * @brief Check the behavior of preemptive threads when the
   * time slice is disabled and enabled
   *
   * @details Create multiple preemptive threads with same priorities
   * and few with same priorities and enable the time slice.
   * Ensure that each thread is given the time slice period to execute.
   *
   * @ingroup kernel_sched_tests
   */
  void test_slice_scheduling(void)
  {
  	k_tid_t tid[NUM_THREAD];
  	int old_prio = k_thread_priority_get(k_current_get());
  	int count = 0;
  
  	/* disable timeslice */
  	k_sched_time_slice_set(0, K_PRIO_PREEMPT(0));
  
  	/* update priority for current thread */
  	k_thread_priority_set(k_current_get(), K_PRIO_PREEMPT(BASE_PRIORITY));
  
  	/* create threads with equal preemptive 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), 0,
  					 K_NO_WAIT);
  	}
  
  	/* enable time slice */
  	k_sched_time_slice_set(SLICE_SIZE, K_PRIO_PREEMPT(BASE_PRIORITY));
  
  	while (count < ITRERATION_COUNT) {
  		k_uptime_delta(&elapsed_slice);
  
  		/* Keep the current thread busy for more than one slice,
  		 * even though, when timeslice used up the next thread
  		 * should be scheduled in.
  		 */
  		spin_for_ms(BUSY_MS);
  
  		/* relinquish CPU and wait for each thread to complete */
  		for (int i = 0; i < NUM_THREAD; i++) {
  			k_sem_take(&sema1, K_FOREVER);
  		}
  		count++;
  	}
  
  
  	/* test case teardown */
  	for (int i = 0; i < NUM_THREAD; i++) {
  		k_thread_abort(tid[i]);
  	}
  
  	/* disable time slice */
  	k_sched_time_slice_set(0, K_PRIO_PREEMPT(0));
  
  	k_thread_priority_set(k_current_get(), old_prio);
  }
  
  #else /* CONFIG_TIMESLICING */
  void test_slice_scheduling(void)
  {
  	ztest_test_skip();
  }
  #endif /* CONFIG_TIMESLICING */
  