atomic-cortex.h

/*
 * Copyright (c) 2019, Toshiba Corporation
 * All rights reserved.
 *
 * 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 of the copyright holder 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 HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */
/*---------------------------------------------------------------------------*/
/**
 * \addtogroup arm
 *
 * Arm Cortex-M implementation of atomic operations using the LDREX,
 * STREX and DMB instructions.
 *
 * @{
 */
#ifndef ATOMIC_CORTEX_H_
#define ATOMIC_CORTEX_H_
#include <contiki.h>
 
#ifdef CMSIS_CONF_HEADER_PATH
#include CMSIS_CONF_HEADER_PATH
#endif
 
#include <stdint.h>
#include <stdbool.h>
 
#define atomic_cas_uint8(t,o,n) atomic_cortex_cas_uint8((t),(o),(n))
 
static inline bool
atomic_cortex_cas_uint8(uint8_t *target, uint8_t old_val, uint8_t new_val)
{
  int status = 1;
  
  if(__LDREXB(target) == old_val) {
    status = __STREXB(new_val, target);
  }
 
  __DMB();
  
  return status == 0 ? true : false;
}
 
#endif /* ATOMIC_CORTEX_H_ */
/** @} */