path: root/cpukit/include/rtems/score/coresemimpl.h

/* SPDX-License-Identifier: BSD-2-Clause */

/**
 * @file
 *
 * @ingroup RTEMSScoreSemaphore
 *
 * @brief This header file provides interfaces of the
 *   @ref RTEMSScoreSemaphore which are only used by the implementation.
 */

/*
 *  COPYRIGHT (c) 1989-2006.
 *  On-Line Applications Research Corporation (OAR).
 *
 * 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.
 *
 * 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 _RTEMS_SCORE_CORESEMIMPL_H
#define _RTEMS_SCORE_CORESEMIMPL_H

#include <rtems/score/coresem.h>
#include <rtems/score/objectimpl.h>
#include <rtems/score/threaddispatch.h>
#include <rtems/score/threadimpl.h>
#include <rtems/score/threadqimpl.h>
#include <rtems/score/statesimpl.h>
#include <rtems/score/status.h>

#ifdef __cplusplus
extern "C" {
#endif

/**
 * @addtogroup RTEMSScoreSemaphore
 *
 * @{
 */

/**
 * @brief Initializes the semaphore based on the parameters passed.
 *
 * This package is the implementation of the CORE Semaphore Handler.
 * This core object utilizes standard Dijkstra counting semaphores to provide
 * synchronization and mutual exclusion capabilities.
 *
 * This routine initializes the semaphore based on the parameters passed.
 *
 * @param[out] the_semaphore The semaphore to initialize.
 * @param initial_value The initial count of the semaphore.
 */
void _CORE_semaphore_Initialize(
  CORE_semaphore_Control *the_semaphore,
  uint32_t                initial_value
);

/**
 * @brief Acquires the semaphore critical.
 *
 * This routine acquires the semaphore.
 *
 * @param[in, out] the_semaphore The semaphore to acquire.
 * @param queue_context The thread queue context.
 */
static inline void _CORE_semaphore_Acquire_critical(
  CORE_semaphore_Control *the_semaphore,
  Thread_queue_Context   *queue_context
)
{
  _Thread_queue_Acquire_critical( &the_semaphore->Wait_queue, queue_context );
}

/**
 * @brief Releases the semaphore.
 *
 * This routine releases the semaphore.
 *
 * @param[in, out] the_semaphore The semaphore to release.
 * @param queue_context The thread queue context.
 */
static inline void _CORE_semaphore_Release(
  CORE_semaphore_Control *the_semaphore,
  Thread_queue_Context   *queue_context
)
{
  _Thread_queue_Release( &the_semaphore->Wait_queue, queue_context );
}

/**
 * @brief Destroys the semaphore.
 *
 * This routine destroys the semaphore.
 *
 * @param[out] the_semaphore The semaphore to destroy.
 * @param operations The thread queue operations.
 * @param queue_context The thread queue context.
 */
static inline void _CORE_semaphore_Destroy(
  CORE_semaphore_Control        *the_semaphore,
  const Thread_queue_Operations *operations,
  Thread_queue_Context          *queue_context
)
{
  _Thread_queue_Flush_critical(
    &the_semaphore->Wait_queue.Queue,
    operations,
    _Thread_queue_Flush_status_object_was_deleted,
    queue_context
  );
  _Thread_queue_Destroy( &the_semaphore->Wait_queue );
}

/**
 * @brief Surrenders a unit to the semaphore.
 *
 * This routine frees a unit to the semaphore.  If a task was blocked waiting
 * for a unit from this semaphore, then that task will be readied and the unit
 * given to that task.  Otherwise, the unit will be returned to the semaphore.
 *
 * @param[in, out] the_semaphore is the semaphore to surrender
 * @param operations The thread queue operations.
 * @param maximum_count The maximum number of units in the semaphore.
 * @param queue_context is a temporary variable used to contain the ISR
 *       disable level cookie.
 *
 * @retval STATUS_SUCCESSFUL The unit was successfully freed to the semaphore.
 * @retval STATUS_MAXIMUM_COUNT_EXCEEDED The maximum number of units was exceeded.
 */
static inline Status_Control _CORE_semaphore_Surrender(
  CORE_semaphore_Control        *the_semaphore,
  const Thread_queue_Operations *operations,
  uint32_t                       maximum_count,
  Thread_queue_Context          *queue_context
)
{
  Status_Control      status;
  Thread_queue_Heads *heads;

  status = STATUS_SUCCESSFUL;

  _CORE_semaphore_Acquire_critical( the_semaphore, queue_context );

  heads = the_semaphore->Wait_queue.Queue.heads;

  if ( heads != NULL ) {
    _Thread_queue_Surrender_no_priority(
      &the_semaphore->Wait_queue.Queue,
      heads,
      queue_context,
      operations
    );
  } else {
    if ( the_semaphore->count < maximum_count )
      the_semaphore->count += 1;
    else
      status = STATUS_MAXIMUM_COUNT_EXCEEDED;

    _CORE_semaphore_Release( the_semaphore, queue_context );
  }

  return status;
}

/**
 * @brief Returns the current count associated with the semaphore.
 *
 * @param the_semaphore The semaphore to obtain the count of.
 *
 * @return the current count of this semaphore.
 */
static inline uint32_t  _CORE_semaphore_Get_count(
  const CORE_semaphore_Control *the_semaphore
)
{
  return the_semaphore->count;
}

/**
 * @brief Seizes the semaphore
 *
 * This routine attempts to receive a unit from the_semaphore.
 * If a unit is available or if the wait flag is false, then the routine
 * returns.  Otherwise, the calling task is blocked until a unit becomes
 * available.
 *
 * @param[in, out] the_semaphore The semaphore to obtain.
 * @param operations The thread queue operations.
 * @param executing The currently executing thread.
 * @param wait Indicates whether the calling thread is willing to wait.
 * @param queue_context is a temporary variable used to contain the ISR
 *        disable level cookie.
 *
 * @retval STATUS_SUCCESSFUL The semaphore was successfully seized.
 * @retval STATUS_UNSATISFIED The semaphore is currently not free and the
 *      calling thread not willing to wait.
 * @retval STATUS_TIMEOUT A timeout occurred.
 */
static inline Status_Control _CORE_semaphore_Seize(
  CORE_semaphore_Control        *the_semaphore,
  const Thread_queue_Operations *operations,
  Thread_Control                *executing,
  bool                           wait,
  Thread_queue_Context          *queue_context
)
{
  _Assert( _ISR_Get_level() != 0 );

  _CORE_semaphore_Acquire_critical( the_semaphore, queue_context );
  if ( the_semaphore->count != 0 ) {
    the_semaphore->count -= 1;
    _CORE_semaphore_Release( the_semaphore, queue_context );
    return STATUS_SUCCESSFUL;
  }

  if ( !wait ) {
    _CORE_semaphore_Release( the_semaphore, queue_context );
    return STATUS_UNSATISFIED;
  }

  _Thread_queue_Context_set_thread_state(
    queue_context,
    STATES_WAITING_FOR_SEMAPHORE
  );
  _Thread_queue_Enqueue(
    &the_semaphore->Wait_queue.Queue,
    operations,
    executing,
    queue_context
  );
  return _Thread_Wait_get_status( executing );
}

/** @} */

#ifdef __cplusplus
}
#endif

#endif
/* end of include file */