source: rtems/cpukit/score/include/rtems/score/smplock.h @ 3ccce23

/**
 * @file
 *
 * @ingroup ScoreSMPLock
 *
 * @brief SMP Lock API
 */

/*
 * COPYRIGHT (c) 1989-2011.
 * On-Line Applications Research Corporation (OAR).
 *
 * Copyright (c) 2013 embedded brains GmbH
 *
 * The license and distribution terms for this file may be
 * found in the file LICENSE in this distribution or at
 * http://www.rtems.com/license/LICENSE.
 */

#ifndef _RTEMS_SCORE_SMPLOCK_H
#define _RTEMS_SCORE_SMPLOCK_H

#include <rtems/score/cpuopts.h>

#if defined( RTEMS_SMP )

#include <rtems/score/cpusmplock.h>
#include <rtems/score/isr.h>

#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */

/**
 * @defgroup ScoreSMPLock SMP Locks
 *
 * @ingroup Score
 *
 * The SMP lock implementation is architecture dependent.  The implementation
 * should provide fairness in case of concurrent lock attempts.  A ticket lock
 * is probably the most likely implementation.
 *
 * This SMP lock API has a flaw.  It does not provide the ability to use a
 * local context for acquire and release pairs.  Such a context is necessary to
 * implement for example the Mellor-Crummey and Scott (MCS) locks.  The SMP
 * lock is currently used in _Thread_Disable_dispatch() and
 * _Thread_Enable_dispatch() and makes them to a giant lock acquire and
 * release.  Since these functions do not pass state information via a local
 * context there is currently no use case for such a feature.
 *
 * @{
 */

/**
 * @brief SMP lock control.
 *
 * This is an opaque type.  The SMP lock implementation is architecture
 * dependent.
 */
typedef CPU_SMP_lock_Control SMP_lock_Control;

/**
 * @brief SMP lock control initializer for static initialization.
 */
#define SMP_LOCK_INITIALIZER CPU_SMP_LOCK_INITIALIZER

/**
 * @brief Initializes a SMP lock control.
 *
 * Concurrent initialization leads to unpredictable results.
 *
 * @param[out] lock The SMP lock control.
 */
static inline void _SMP_lock_Initialize( SMP_lock_Control *lock )
{
  _CPU_SMP_lock_Initialize( lock );
}

/**
 * @brief Acquires a SMP lock.
 *
 * This function will not disable interrupts.  The caller must ensure that the
 * current thread of execution is not interrupted indefinite once it obtained
 * the SMP lock.
 *
 * @param[in/out] lock The SMP lock control.
 */
static inline void _SMP_lock_Acquire( SMP_lock_Control *lock )
{
  _CPU_SMP_lock_Acquire( lock );
}

/**
 * @brief Releases a SMP lock.
 *
 * @param[in/out] lock The SMP lock control.
 */
static inline void _SMP_lock_Release( SMP_lock_Control *lock )
{
  _CPU_SMP_lock_Release( lock );
}

/**
 * @brief Disables interrupts and acquires the SMP lock.
 *
 * @param[in/out] lock The SMP lock control.
 * @param[out] isr_cookie The ISR cookie.
 */
#define _SMP_lock_ISR_disable_and_acquire( lock, isr_cookie ) \
  _CPU_SMP_lock_ISR_disable_and_acquire( lock, isr_cookie )

/**
 * @brief Releases the SMP lock and enables interrupts.
 *
 * @param[in/out] lock The SMP lock control.
 * @param[in] isr_cookie The ISR cookie.
 */
#define _SMP_lock_Release_and_ISR_enable( lock, isr_cookie ) \
  _CPU_SMP_lock_Release_and_ISR_enable( lock, isr_cookie )

/**@}*/

#ifdef __cplusplus
}
#endif /* __cplusplus */

#endif /* defined( RTEMS_SMP ) */

#endif /* _RTEMS_SCORE_SMPLOCK_H */