/* Copyright (c) 2014, Linaro Limited
 * All rights reserved.
 *
 * SPDX-License-Identifier:     BSD-3-Clause
 */

#ifndef ODP_RWLOCK_H_
#define ODP_RWLOCK_H_

/**
 * @file
 *
 * ODP RW Locks
 */

#include <odp_atomic.h>

#ifdef __cplusplus
extern "C" {
#endif

/** @defgroup odp_synchronizers ODP SYNCRONIZERS
 *  Operations on reader/writer locks.
 *  A reader/writer lock allows multiple simultaneous readers but only one
 *  writer at a time.
 *  A thread that wants write access will have to wait until there are no
 *  threads that want read access. This casues a risk for starvation.
 *  @{
 */

/**
 * The odp_rwlock_t type.
 */
typedef struct {
	odp_atomic_u32_t cnt; /**< @private lock count
				0 lock not taken
				-1 write lock taken
				>0 read lock(s) taken */
} odp_rwlock_t;


/**
 * Initialize a reader/writer lock.
 *
 * @param rwlock Pointer to a reader/writer lock
 */
void odp_rwlock_init(odp_rwlock_t *rwlock);

/**
 * Acquire read permission on a reader/writer lock.
 *
 * @param rwlock Pointer to a reader/writer lock
 */
void odp_rwlock_read_lock(odp_rwlock_t *rwlock);

/**
 * Release read permission on a reader/writer lock.
 *
 * @param rwlock Pointer to a reader/writer lock
 */
void odp_rwlock_read_unlock(odp_rwlock_t *rwlock);

/**
 * Acquire write permission on a reader/writer lock.
 *
 * @param rwlock Pointer to a reader/writer lock
 */
void odp_rwlock_write_lock(odp_rwlock_t *rwlock);

/**
 * Release write permission on a reader/writer lock.
 *
 * @param rwlock Pointer to a reader/writer lock
 */
void odp_rwlock_write_unlock(odp_rwlock_t *rwlock);

/**
 * @}
 */

#ifdef __cplusplus
}
#endif

#endif /* ODP_RWLOCK_H_ */