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/* SPDX-License-Identifier: BSD-2-Clause */
/**
* @file
*
* @ingroup RTEMSScoreSMPLock
*
* @brief This header file provides the interfaces of the
* @ref RTEMSScoreSMPLock related to ticket locks.
*/
/*
* Copyright (c) 2013, 2016 embedded brains GmbH
*
* 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 */
/**
* @addtogroup RTEMSScoreSMPLock
*
* @{
*/
/**
* @brief SMP ticket lock control.
*/
typedef struct {
Atomic_Uint next_ticket;
Atomic_Uint now_serving;
} SMP_ticket_lock_Control;
/**
* @brief SMP ticket lock control initializer for static initialization.
*/
#define SMP_TICKET_LOCK_INITIALIZER \
{ \
ATOMIC_INITIALIZER_UINT( 0U ), \
ATOMIC_INITIALIZER_UINT( 0U ) \
}
/**
* @brief Initializes the SMP ticket lock.
*
* Concurrent initialization leads to unpredictable results.
*
* @param[in, out] lock The SMP ticket lock control.
*/
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 );
}
/**
* @brief Destroys the SMP ticket lock.
*
* Concurrent destruction leads to unpredictable results.
*
* @param lock The SMP ticket lock control.
*/
static inline void _SMP_ticket_lock_Destroy( SMP_ticket_lock_Control *lock )
{
(void) lock;
}
/**
* @brief Acquires the SMP ticket lock.
*
* @param[in, out] lock The lock to acquire.
* @param stats The SMP lock statistics.
* @param[out] stats_context The context for the statistics.
*/
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
}
/**
* @brief Acquires an SMP ticket 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 ticket lock.
*
* @param[in] lock The SMP ticket lock control.
* @param[in] stats The SMP lock statistics.
* @param[out] stats_context The SMP lock statistics context.
*/
#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
/**
* @brief Releases the SMP ticket lock.
*
* @param[in, out] lock The SMP ticket lock to release.
* @param[out] stats_context The SMP lock statistics context.
*/
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 );
}
/**
* @brief Releases an SMP ticket lock.
*
* @param[in] lock The SMP ticket lock control.
* @param[in] stats_context The SMP lock statistics context.
*/
#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 */
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