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/**
* @file
*
* @ingroup RTEMSScoreSMPLock
*
* @brief SMP Lock API
*/
/*
* Copyright (c) 2013, 2016 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.org/license/LICENSE.
*/
#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 an SMP ticket lock.
*
* Concurrent initialization leads to unpredictable results.
*
* @param[in] 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 an SMP ticket lock.
*
* Concurrent destruction leads to unpredictable results.
*
* @param[in] lock The SMP ticket lock control.
*/
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
}
/**
* @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
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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