File content as of revision 150:02e0a0aed4ec:

/*******************************************************************************
 * Copyright (C) 2016 Maxim Integrated Products, Inc., All Rights Reserved.
 *
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 * The above copyright notice and this permission notice shall be included
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 *
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 * $Date: 2016-03-11 11:46:37 -0600 (Fri, 11 Mar 2016) $
 * $Revision: 21839 $
 *
 ******************************************************************************/

/**
 * @file    mxc_lock.h
 * @brief   Used to create exclusion for critical sections.
 */

#ifndef _MXC_LOCK_H_
#define _MXC_LOCK_H_

#ifdef __cplusplus
extern "C" {
#endif

/***** Includes *****/
#include "mxc_config.h"

/***** Definitions *****/

/***** Globals *****/

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

/**
 * @brief   Attempts to acquire the lock.
 * @param   lock    Pointer to variable used for the lock.
 * @param   value   Value to be place in the lock. Can not be 0.
 * @details This in an interrupt safe function that can be used as a mutex.
            The lock variable must remain in scope until the lock is released.
            Will not block if another thread has acquired the lock.
 * @returns E_NO_ERROR if everything successful, E_BUSY if lock is taken.
 */
__STATIC_INLINE int mxc_get_lock(uint32_t *lock, uint32_t value)
{
    do {

        // Return if the lock is taken by a different thread
        if(__LDREXW((volatile unsigned long *)lock) != 0) {
            return E_BUSY;
        }

        // Attempt to take the lock
    } while(__STREXW(value, (volatile unsigned long *)lock) != 0);

    // Do not start any other memory access until memory barrier is complete
    __DMB();

    return E_NO_ERROR;
}

/**
 * @brief   Free the given lock.
 * @param   lock    Pointer to variable used for the lock.
 */
__STATIC_INLINE void mxc_free_lock(uint32_t *lock)
{
    // Ensure memory operations complete before releasing lock
    __DMB();
    *lock = 0;
}

#ifdef __cplusplus
}
#endif

#endif /* _MXC_LOCK_H_ */