smplockticket.h

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/* SPDX-License-Identifier: BSD-2-Clause */
 
/*
 * Copyright (C) 2013, 2016 embedded brains GmbH & Co. KG
 *
 * 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_SMPLOCKTICKET_H
#define _RTEMS_SCORE_SMPLOCKTICKET_H
 
#include <rtems/score/cpuopts.h>
 
#if defined(RTEMS_SMP)
 
#include <rtems/score/atomic.h>
#include <rtems/score/smplockstats.h>
 
#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */
 
typedef struct {
  Atomic_Uint next_ticket;
  Atomic_Uint now_serving;
} SMP_ticket_lock_Control;
 
#define SMP_TICKET_LOCK_INITIALIZER \
  { \
    ATOMIC_INITIALIZER_UINT( 0U ), \
    ATOMIC_INITIALIZER_UINT( 0U ) \
  }
 
static inline void _SMP_ticket_lock_Initialize(
  SMP_ticket_lock_Control *lock
)
{
  _Atomic_Init_uint( &lock->next_ticket, 0U );
  _Atomic_Init_uint( &lock->now_serving, 0U );
}
 
static inline void _SMP_ticket_lock_Destroy( SMP_ticket_lock_Control *lock )
{
  (void) lock;
}
 
static inline void _SMP_ticket_lock_Do_acquire(
  SMP_ticket_lock_Control *lock
#if defined(RTEMS_PROFILING)
  ,
  SMP_lock_Stats          *stats,
  SMP_lock_Stats_context  *stats_context
#endif
)
{
  unsigned int                   my_ticket;
  unsigned int                   now_serving;
#if defined(RTEMS_PROFILING)
  unsigned int                   initial_queue_length;
  SMP_lock_Stats_acquire_context acquire_context;
 
  _SMP_lock_Stats_acquire_begin( &acquire_context );
#endif
 
  my_ticket =
    _Atomic_Fetch_add_uint( &lock->next_ticket, 1U, ATOMIC_ORDER_RELAXED );
 
#if defined(RTEMS_PROFILING)
  now_serving =
    _Atomic_Load_uint( &lock->now_serving, ATOMIC_ORDER_ACQUIRE );
  initial_queue_length = my_ticket - now_serving;
 
  if ( initial_queue_length > 0 ) {
#endif
 
    do {
      now_serving =
        _Atomic_Load_uint( &lock->now_serving, ATOMIC_ORDER_ACQUIRE );
    } while ( now_serving != my_ticket );
 
#if defined(RTEMS_PROFILING)
  }
 
  _SMP_lock_Stats_acquire_end(
    &acquire_context,
    stats,
    stats_context,
    initial_queue_length
  );
#endif
}
 
#if defined(RTEMS_PROFILING)
  #define _SMP_ticket_lock_Acquire( lock, stats, stats_context ) \
    _SMP_ticket_lock_Do_acquire( lock, stats, stats_context )
#else
  #define _SMP_ticket_lock_Acquire( lock, stats, stats_context ) \
    _SMP_ticket_lock_Do_acquire( lock )
#endif
 
static inline void _SMP_ticket_lock_Do_release(
  SMP_ticket_lock_Control *lock
#if defined(RTEMS_PROFILING)
  ,
  const SMP_lock_Stats_context *stats_context
#endif
)
{
  unsigned int current_ticket =
    _Atomic_Load_uint( &lock->now_serving, ATOMIC_ORDER_RELAXED );
  unsigned int next_ticket = current_ticket + 1U;
 
#if defined(RTEMS_PROFILING)
  _SMP_lock_Stats_release_update( stats_context );
#endif
 
  _Atomic_Store_uint( &lock->now_serving, next_ticket, ATOMIC_ORDER_RELEASE );
}
 
#if defined(RTEMS_PROFILING)
  #define _SMP_ticket_lock_Release( lock, stats_context ) \
    _SMP_ticket_lock_Do_release( lock, stats_context )
#else
  #define _SMP_ticket_lock_Release( lock, stats_context ) \
    _SMP_ticket_lock_Do_release( lock )
#endif
 
#ifdef __cplusplus
}
#endif /* __cplusplus */
 
#endif /* RTEMS_SMP */
 
#endif /* _RTEMS_SCORE_SMPLOCKTICKET_H */