kernel/include/ksched.h

/*
 * Copyright (c) 2016-2017 Wind River Systems, Inc.
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#ifndef ZEPHYR_KERNEL_INCLUDE_KSCHED_H_
#define ZEPHYR_KERNEL_INCLUDE_KSCHED_H_

#include <zephyr/kernel_structs.h>
#include <kernel_internal.h>
#include <timeout_q.h>
#include <kthread.h>
#include <zephyr/tracing/tracing.h>
#include <stdbool.h>
#include <priority_q.h>

BUILD_ASSERT(K_LOWEST_APPLICATION_THREAD_PRIO
	     >= K_HIGHEST_APPLICATION_THREAD_PRIO);

#ifdef CONFIG_MULTITHREADING
#define Z_VALID_PRIO(prio, entry_point)				     \
	(((prio) == K_IDLE_PRIO && z_is_idle_thread_entry(entry_point)) || \
	 ((K_LOWEST_APPLICATION_THREAD_PRIO			     \
	   >= K_HIGHEST_APPLICATION_THREAD_PRIO)		     \
	  && (prio) >= K_HIGHEST_APPLICATION_THREAD_PRIO	     \
	  && (prio) <= K_LOWEST_APPLICATION_THREAD_PRIO))

#define Z_ASSERT_VALID_PRIO(prio, entry_point) do { \
	__ASSERT(Z_VALID_PRIO((prio), (entry_point)), \
		 "invalid priority (%d); allowed range: %d to %d", \
		 (prio), \
		 K_LOWEST_APPLICATION_THREAD_PRIO, \
		 K_HIGHEST_APPLICATION_THREAD_PRIO); \
	} while (false)
#else
#define Z_VALID_PRIO(prio, entry_point) ((prio) == -1)
#define Z_ASSERT_VALID_PRIO(prio, entry_point) __ASSERT((prio) == -1, "")
#endif /* CONFIG_MULTITHREADING */

#if (CONFIG_MP_MAX_NUM_CPUS == 1)
#define LOCK_SCHED_SPINLOCK
#else
#define LOCK_SCHED_SPINLOCK   K_SPINLOCK(&_sched_spinlock)
#endif

#ifdef __cplusplus
extern "C" {
#endif

extern struct k_spinlock _sched_spinlock;

extern struct k_thread _thread_dummy;

void z_sched_init(void);
void z_unpend_thread_no_timeout(struct k_thread *thread);
struct k_thread *z_unpend1_no_timeout(_wait_q_t *wait_q);
int z_pend_curr(struct k_spinlock *lock, k_spinlock_key_t key,
	       _wait_q_t *wait_q, k_timeout_t timeout);
void z_pend_thread(struct k_thread *thread, _wait_q_t *wait_q,
		   k_timeout_t timeout);
void z_reschedule(struct k_spinlock *lock, k_spinlock_key_t key);
void z_reschedule_irqlock(uint32_t key);
void z_unpend_thread(struct k_thread *thread);
int z_unpend_all(_wait_q_t *wait_q);
bool z_thread_prio_set(struct k_thread *thread, int prio);
void *z_get_next_switch_handle(void *interrupted);

void z_time_slice(void);
void z_reset_time_slice(struct k_thread *curr);
void z_sched_start(struct k_thread *thread);
void z_ready_thread(struct k_thread *thread);
void z_requeue_current(struct k_thread *curr);
struct k_thread *z_swap_next_thread(void);
void move_current_to_end_of_prio_q(void);
bool thread_is_sliceable(struct k_thread *thread);

static inline void z_reschedule_unlocked(void)
{
	(void) z_reschedule_irqlock(arch_irq_lock());
}

static inline bool z_is_under_prio_ceiling(int prio)
{
	return prio >= CONFIG_PRIORITY_CEILING;
}

static inline int z_get_new_prio_with_ceiling(int prio)
{
	return z_is_under_prio_ceiling(prio) ? prio : CONFIG_PRIORITY_CEILING;
}

static inline bool z_is_prio1_higher_than_or_equal_to_prio2(int prio1, int prio2)
{
	return prio1 <= prio2;
}

static inline bool z_is_prio_higher_or_equal(int prio1, int prio2)
{
	return z_is_prio1_higher_than_or_equal_to_prio2(prio1, prio2);
}

static inline bool z_is_prio1_lower_than_or_equal_to_prio2(int prio1, int prio2)
{
	return prio1 >= prio2;
}

static inline bool z_is_prio1_higher_than_prio2(int prio1, int prio2)
{
	return prio1 < prio2;
}

static inline bool z_is_prio_higher(int prio, int test_prio)
{
	return z_is_prio1_higher_than_prio2(prio, test_prio);
}

static inline bool z_is_prio_lower_or_equal(int prio1, int prio2)
{
	return z_is_prio1_lower_than_or_equal_to_prio2(prio1, prio2);
}

static inline bool _is_valid_prio(int prio, k_thread_entry_t entry_point)
{
	if ((prio == K_IDLE_PRIO) && z_is_idle_thread_entry(entry_point)) {
		return true;
	}

	if (!z_is_prio_higher_or_equal(prio,
				       K_LOWEST_APPLICATION_THREAD_PRIO)) {
		return false;
	}

	if (!z_is_prio_lower_or_equal(prio,
				      K_HIGHEST_APPLICATION_THREAD_PRIO)) {
		return false;
	}

	return true;
}

static ALWAYS_INLINE _wait_q_t *pended_on_thread(struct k_thread *thread)
{
	__ASSERT_NO_MSG(thread->base.pended_on);

	return thread->base.pended_on;
}


static inline void unpend_thread_no_timeout(struct k_thread *thread)
{
	_priq_wait_remove(&pended_on_thread(thread)->waitq, thread);
	z_mark_thread_as_not_pending(thread);
	thread->base.pended_on = NULL;
}

/*
 * In a multiprocessor system, z_unpend_first_thread() must lock the scheduler
 * spinlock _sched_spinlock. However, in a uniprocessor system, that is not
 * necessary as the caller has already taken precautions (in the form of
 * locking interrupts).
 */
static ALWAYS_INLINE struct k_thread *z_unpend_first_thread(_wait_q_t *wait_q)
{
	struct k_thread *thread = NULL;

	__ASSERT_EVAL(, int key = arch_irq_lock(); arch_irq_unlock(key),
		      !arch_irq_unlocked(key), "");

	LOCK_SCHED_SPINLOCK {
		thread = _priq_wait_best(&wait_q->waitq);
		if (unlikely(thread != NULL)) {
			unpend_thread_no_timeout(thread);
			z_abort_thread_timeout(thread);
		}
	}

	return thread;
}

/*
 * APIs for working with the Zephyr kernel scheduler. Intended for use in
 * management of IPC objects, either in the core kernel or other IPC
 * implemented by OS compatibility layers, providing basic wait/wake operations
 * with spinlocks used for synchronization.
 *
 * These APIs are public and will be treated as contract, even if the
 * underlying scheduler implementation changes.
 */

/**
 * Wake up a thread pending on the provided wait queue
 *
 * Given a wait_q, wake up the highest priority thread on the queue. If the
 * queue was empty just return false.
 *
 * Otherwise, do the following, in order,  holding _sched_spinlock the entire
 * time so that the thread state is guaranteed not to change:
 * - Set the thread's swap return values to swap_retval and swap_data
 * - un-pend and ready the thread, but do not invoke the scheduler.
 *
 * Repeated calls to this function until it returns false is a suitable
 * way to wake all threads on the queue.
 *
 * It is up to the caller to implement locking such that the return value of
 * this function (whether a thread was woken up or not) does not immediately
 * become stale. Calls to wait and wake on the same wait_q object must have
 * synchronization. Calling this without holding any spinlock is a sign that
 * this API is not being used properly.
 *
 * @param wait_q Wait queue to wake up the highest prio thread
 * @param swap_retval Swap return value for woken thread
 * @param swap_data Data return value to supplement swap_retval. May be NULL.
 * @retval true If a thread was woken up
 * @retval false If the wait_q was empty
 */
bool z_sched_wake(_wait_q_t *wait_q, int swap_retval, void *swap_data);

/**
 * Wakes the specified thread.
 *
 * Given a specific thread, wake it up. This routine assumes that the given
 * thread is not on the timeout queue.
 *
 * @param thread Given thread to wake up.
 * @param is_timeout True if called from the timer ISR; false otherwise.
 *
 */
void z_sched_wake_thread(struct k_thread *thread, bool is_timeout);

/**
 * Wake up all threads pending on the provided wait queue
 *
 * Convenience function to invoke z_sched_wake() on all threads in the queue
 * until there are no more to wake up.
 *
 * @param wait_q Wait queue to wake up the highest prio thread
 * @param swap_retval Swap return value for woken thread
 * @param swap_data Data return value to supplement swap_retval. May be NULL.
 * @retval true If any threads were woken up
 * @retval false If the wait_q was empty
 */
static inline bool z_sched_wake_all(_wait_q_t *wait_q, int swap_retval,
				    void *swap_data)
{
	bool woken = false;

	while (z_sched_wake(wait_q, swap_retval, swap_data)) {
		woken = true;
	}

	/* True if we woke at least one thread up */
	return woken;
}

/**
 * Atomically put the current thread to sleep on a wait queue, with timeout
 *
 * The thread will be added to the provided waitqueue. The lock, which should
 * be held by the caller with the provided key, will be released once this is
 * completely done and we have swapped out.
 *
 * The return value and data pointer is set by whoever woke us up via
 * z_sched_wake.
 *
 * @param lock Address of spinlock to release when we swap out
 * @param key Key to the provided spinlock when it was locked
 * @param wait_q Wait queue to go to sleep on
 * @param timeout Waiting period to be woken up, or K_FOREVER to wait
 *                indefinitely.
 * @param data Storage location for data pointer set when thread was woken up.
 *             May be NULL if not used.
 * @retval Return value set by whatever woke us up, or -EAGAIN if the timeout
 *         expired without being woken up.
 */
int z_sched_wait(struct k_spinlock *lock, k_spinlock_key_t key,
		 _wait_q_t *wait_q, k_timeout_t timeout, void **data);

/**
 * @brief Walks the wait queue invoking the callback on each waiting thread
 *
 * This function walks the wait queue invoking the callback function on each
 * waiting thread while holding _sched_spinlock. This can be useful for routines
 * that need to operate on multiple waiting threads.
 *
 * CAUTION! As a wait queue is of indeterminate length, the scheduler will be
 * locked for an indeterminate amount of time. This may impact system
 * performance. As such, care must be taken when using both this function and
 * the specified callback.
 *
 * @param wait_q Identifies the wait queue to walk
 * @param func   Callback to invoke on each waiting thread
 * @param data   Custom data passed to the callback
 *
 * @retval non-zero if walk is terminated by the callback; otherwise 0
 */
int z_sched_waitq_walk(_wait_q_t *wait_q,
		       int (*func)(struct k_thread *, void *), void *data);

/** @brief Halt thread cycle usage accounting.
 *
 * Halts the accumulation of thread cycle usage and adds the current
 * total to the thread's counter.  Called on context switch.
 *
 * Note that this function is idempotent.  The core kernel code calls
 * it at the end of interrupt handlers (because that is where we have
 * a portable hook) where we are context switching, which will include
 * any cycles spent in the ISR in the per-thread accounting.  But
 * architecture code can also call it earlier out of interrupt entry
 * to improve measurement fidelity.
 *
 * This function assumes local interrupts are masked (so that the
 * current CPU pointer and current thread are safe to modify), but
 * requires no other synchronization.  Architecture layers don't need
 * to do anything more.
 */
void z_sched_usage_stop(void);

void z_sched_usage_start(struct k_thread *thread);

/**
 * @brief Retrieves CPU cycle usage data for specified core
 */
void z_sched_cpu_usage(uint8_t core_id, struct k_thread_runtime_stats *stats);

/**
 * @brief Retrieves thread cycle usage data for specified thread
 */
void z_sched_thread_usage(struct k_thread *thread,
			  struct k_thread_runtime_stats *stats);

static inline void z_sched_usage_switch(struct k_thread *thread)
{
	ARG_UNUSED(thread);
#ifdef CONFIG_SCHED_THREAD_USAGE
	z_sched_usage_stop();
	z_sched_usage_start(thread);
#endif /* CONFIG_SCHED_THREAD_USAGE */
}

#ifdef __cplusplus
}
#endif

#endif /* ZEPHYR_KERNEL_INCLUDE_KSCHED_H_ */