eduOS/include/eduos/spinlock.h

/*
 * Copyright (c) 2011, Stefan Lankes, RWTH Aachen University
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *    * Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *    * Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *    * Neither the name of the University nor the names of its contributors
 *      may be used to endorse or promote products derived from this
 *      software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * @author Stefan Lankes
 * @file include/eduos/spinlock.h
 * @brief Spinlock functions
 */

#ifndef __SPINLOCK_H__
#define __SPINLOCK_H__

#include <eduos/stddef.h>
#include <eduos/spinlock_types.h>
#include <eduos/tasks_types.h>
#include <eduos/errno.h>
#include <asm/atomic.h>
#include <asm/processor.h>
#include <asm/irqflags.h>

#ifdef __cplusplus
extern "C" {
#endif

/** @brief Initialization of a spinlock
 *
 * Initialize each spinlock before use!
 *
 * @param s Pointer to the spinlock structure to initialize.
 * @return
 * - 0 on success
 * - -EINVAL (-22) on failure
 */
inline static int spinlock_init(spinlock_t* s) {
	if (BUILTIN_EXPECT(!s, 0))
		return -EINVAL;

	atomic_int32_set(&s->queue, 0);
	atomic_int32_set(&s->dequeue, 1);
	s->owner = MAX_TASKS;
	s->counter = 0;

	return 0;
}

/** @brief Destroy spinlock after use
 * @return 
 * - 0 on success
 * - -EINVAL (-22) on failure
 */
inline static int spinlock_destroy(spinlock_t* s) {
	if (BUILTIN_EXPECT(!s, 0))
		return -EINVAL;

	s->owner = MAX_TASKS;
	s->counter = 0;

	return 0;
}

/** @brief Lock spinlock at entry of critical section 
 * @return
 * - 0 on success
 * - -EINVAL (-22) on failure
 */
inline static int spinlock_lock(spinlock_t* s) {
	int32_t ticket;

	if (BUILTIN_EXPECT(!s, 0))
		return -EINVAL;

	if (s->owner == current_task->id) {
		s->counter++;
		return 0;
	}

	ticket = atomic_int32_add(&s->queue, 1);
	while(atomic_int32_read(&s->dequeue) != ticket) {
		PAUSE;
	}
	s->owner = current_task->id;
	s->counter = 1;

	return 0;
}

/** @brief Unlock spinlock on exit of critical section 
 * @return 
 * - 0 on success
 * - -EINVAL (-22) on failure
 */
inline static int spinlock_unlock(spinlock_t* s) {
	if (BUILTIN_EXPECT(!s, 0))
		return -EINVAL;

	s->counter--;
	if (!s->counter) {
		s->owner = MAX_TASKS;
		atomic_int32_inc(&s->dequeue);
	}

	return 0;
}

/** @brief Initialization of a irqsave spinlock
 *
 * Initialize each irqsave spinlock before use!
 *
 * @return 
 * - 0 on success
 * - -EINVAL (-22) on failure
 */
inline static int spinlock_irqsave_init(spinlock_irqsave_t* s) {
	if (BUILTIN_EXPECT(!s, 0))
		return -EINVAL;

	atomic_int32_set(&s->queue, 0);
	atomic_int32_set(&s->dequeue, 1);
	s->flags = 0;
	s->counter = 0;

	return 0;
}

/** @brief Destroy irqsave spinlock after use
 * @return 
 * - 0 on success
 * - -EINVAL (-22) on failure
 */
inline static int spinlock_irqsave_destroy(spinlock_irqsave_t* s) {
	if (BUILTIN_EXPECT(!s, 0))
		return -EINVAL;

	s->flags = 0;
	s->counter = 0;

	return 0;
}

/** @brief Unlock an irqsave spinlock on exit of critical section 
 * @return 
 * - 0 on success
 * - -EINVAL (-22) on failure
 */
inline static int spinlock_irqsave_lock(spinlock_irqsave_t* s) {
	int32_t ticket;
	uint8_t flags;

	if (BUILTIN_EXPECT(!s, 0))
		return -EINVAL;

	flags = irq_nested_disable();
	if (s->counter == 1) {
		s->counter++;
		return 0;
	}

	ticket = atomic_int32_add(&s->queue, 1);
	while (atomic_int32_read(&s->dequeue) != ticket) {
		PAUSE;
	}

	s->flags = flags;
	s->counter = 1;

	return 0;
}

/** @brief Unlock irqsave spinlock on exit of critical section and re-enable interrupts
 * @return 
 * - 0 on success
 * - -EINVAL (-22) on failure
 */
inline static int spinlock_irqsave_unlock(spinlock_irqsave_t* s) {
	uint8_t flags;

	if (BUILTIN_EXPECT(!s, 0))
		return -EINVAL;

	s->counter--;
	if (!s->counter) {
		flags = s->flags;
		s->flags = 0;
                atomic_int32_inc(&s->dequeue);
		irq_nested_enable(flags);
	}

	return 0;
}

#ifdef __cplusplus
}
#endif

#endif