nuttx/include/nuttx/mutex.h

/****************************************************************************
 * include/nuttx/mutex.h
 *
 *   Copyright (C) 2017 Pinecone Inc. All rights reserved.
 *   Author: Qian Wenfa <qianwenfa@pinecone.net>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 * 3. Neither the name NuttX 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
 * COPYRIGHT OWNER 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.
 *
 ****************************************************************************/

#ifndef __INCLUDE_NUTTX_MUTEX_H
#define __INCLUDE_NUTTX_MUTEX_H

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <stdbool.h>
#include <errno.h>
#include <assert.h>
#include <nuttx/semaphore.h>

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

#define MUTEX_INITIALIZER    SEM_INITIALIZER(1);

/****************************************************************************
 * Public Type Definitions
 ****************************************************************************/

typedef sem_t mutex_t;

/****************************************************************************
 * Public Function Prototypes
 ****************************************************************************/

#ifndef __ASSEMBLY__

#ifdef __cplusplus
#define EXTERN extern "C"
extern "C"
{
#else
#define EXTERN extern
#endif

/****************************************************************************
 * Name: nxmutex_init
 *
 * Description:
 *   This function initializes the UNAMED mutex. Following a
 *   successful call to nxmutex_init(), the mutex may be used in subsequent
 *   calls to nxmutex_lock(), nxmutex_unlock(), and nxmutex_trylock().  The mutex
 *   remains usable until it is destroyed.
 *
 * Parameters:
 *   mutex - Semaphore to be initialized
 *
 * Return Value:
 *   This is an internal OS interface and should not be used by applications.
 *   It follows the NuttX internal error return policy:  Zero (OK) is
 *   returned on success.  A negated errno value is returned on failure.
 *
 ****************************************************************************/

static inline int nxmutex_init(FAR mutex_t *mutex)
{
  return nxsem_init(mutex, 0, 1);
}

/****************************************************************************
 * Name: nxmutex_destroy
 *
 * Description:
 *   This function initializes the UNAMED mutex. Following a
 *   successful call to nxmutex_init(), the mutex may be used in subsequent
 *   calls to nxmutex_lock(), nxmutex_unlock(), and nxmutex_trylock().  The mutex
 *   remains usable until it is destroyed.
 *
 * Parameters:
 *   mutex - Semaphore to be destroyed
 *
 * Return Value:
 *   This is an internal OS interface and should not be used by applications.
 *   It follows the NuttX internal error return policy:  Zero (OK) is
 *   returned on success.  A negated errno value is returned on failure.
 *
 ****************************************************************************/

static inline int nxmutex_destroy(FAR mutex_t *mutex)
{
  return nxsem_destroy(mutex);
}

/****************************************************************************
 * Name: nxmutex_lock
 *
 * Description:
 *   This function attempts to lock the mutex referenced by 'mutex'.  The mutex
 *   is implemented with a semaphore, so if the semaphore value is (<=) zero,
 *   then the calling task will not return until it successfully acquires the lock.
 *
 * Parameters:
 *   mutex - mutex descriptor.
 *
 * Return Value:
 *   This is an internal OS interface and should not be used by applications.
 *   It follows the NuttX internal error return policy:  Zero (OK) is
 *   returned on success.  A negated errno value is returned on failure.
 *   Possible returned errors:
 *
 ****************************************************************************/

static inline int nxmutex_lock(FAR mutex_t *mutex)
{
  return nxsem_wait_uninterruptible(mutex);
}

/****************************************************************************
 * Name: nxmutex_trylock
 *
 * Description:
 *   This function locks the mutex only if the mutex is currently not locked.
 *   If the mutex has been locked already, the call returns without blocking.
 *
 * Parameters:
 *   mutex - mutex descriptor.
 *
 * Return Value:
 *   This is an internal OS interface and should not be used by applications.
 *   It follows the NuttX internal error return policy:  Zero (OK) is
 *   returned on success.  A negated errno value is returned on failure.
 *   Possible returned errors:
 *
 *     -EINVAL - Invalid attempt to lock the mutex
 *     -EAGAIN - The mutex is not available.
 *
 ****************************************************************************/

static inline int nxmutex_trylock(FAR mutex_t *mutex)
{
  return nxsem_trywait(mutex);
}

/****************************************************************************
 * Name: nxmutex_is_locked
 *
 * Description:
 *   This function get the lock state the mutex referenced by 'mutex'.
 *
 * Parameters:
 *   mutex - mutex descriptor.
 *
 * Return Value:
 *
 ****************************************************************************/

static inline bool nxmutex_is_locked(FAR mutex_t *mutex)
{
  int cnt;
  int ret;

  ret = nxsem_getvalue(mutex, &cnt);

  DEBUGASSERT(ret == OK);

  return cnt < 1;
}

/****************************************************************************
 * Name: nxmutex_unlock
 *
 * Description:
 *   This function attempts to unlock the mutex referenced by 'mutex'.
 *
 * Parameters:
 *   mutex - mutex descriptor.
 *
 * Return Value:
 *   This is an internal OS interface and should not be used by applications.
 *   It follows the NuttX internal error return policy:  Zero (OK) is
 *   returned on success.  A negated errno value is returned on failure.
 *   Possible returned errors:
 *
 * Assumptions:
 *   This function may be called from an interrupt handler.
 *
 ****************************************************************************/

static inline int nxmutex_unlock(FAR mutex_t *mutex)
{
  return nxsem_post(mutex);
}

#undef EXTERN
#ifdef __cplusplus
}
#endif

#endif /* __ASSEMBLY__ */
#endif /* __INCLUDE_NUTTX_MUTEX_H */