diff options
Diffstat (limited to 'cpukit/include/rtems/score/smplockticket.h')
| -rw-r--r-- | cpukit/include/rtems/score/smplockticket.h | 187 |
1 files changed, 187 insertions, 0 deletions
diff --git a/cpukit/include/rtems/score/smplockticket.h b/cpukit/include/rtems/score/smplockticket.h new file mode 100644 index 0000000000..e04c4056a5 --- /dev/null +++ b/cpukit/include/rtems/score/smplockticket.h @@ -0,0 +1,187 @@ +/** + * @file + * + * @ingroup ScoreSMPLock + * + * @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 ScoreSMPLock + * + * @{ + */ + +/** + * @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 */ |