score/src/once.c

0001 /**
0002  * @file
0003  *
0004  * @ingroup RTEMSScoreOnce
0005  *
0006  * @brief This source file contains the implementation of
0007  *   _Once(), _Once_Lock(), and _Once_Unlock().
0008  */
0009
0010 /*
0011  * SPDX-License-Identifier: BSD-2-Clause
0012  *
0013  * Copyright (C) 2019 embedded brains GmbH & Co. KG
0014  * Copyright (C) 2019 Sebastian Huber
0015  *
0016  * Redistribution and use in source and binary forms, with or without
0017  * modification, are permitted provided that the following conditions
0018  * are met:
0019  * 1. Redistributions of source code must retain the above copyright
0020  *    notice, this list of conditions and the following disclaimer.
0021  * 2. Redistributions in binary form must reproduce the above copyright
0022  *    notice, this list of conditions and the following disclaimer in the
0023  *    documentation and/or other materials provided with the distribution.
0024  *
0025  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
0026  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
0027  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
0028  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
0029  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
0030  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
0031  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
0032  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
0033  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
0034  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
0035  * POSSIBILITY OF SUCH DAMAGE.
0036  */
0037
0038 #ifdef HAVE_CONFIG_H
0039 #include "config.h"
0040 #endif
0041
0042 #include <rtems/score/onceimpl.h>
0043 #include <rtems/score/threadimpl.h>
0044 #include <rtems/thread.h>
0045
0046 #define ONCE_STATE_INIT 0
0047
0048 #define ONCE_STATE_RUNNING 1
0049
0050 #define ONCE_STATE_COMPLETE 2
0051
0052 typedef struct {
0053   rtems_mutex              Mutex;
0054   rtems_condition_variable State;
0055 } Once_Control;
0056
0057 static Once_Control _Once_Information = {
0058   .Mutex = RTEMS_MUTEX_INITIALIZER( "_Once" ),
0059   .State = RTEMS_CONDITION_VARIABLE_INITIALIZER( "_Once" )
0060 };
0061
0062 static Thread_Life_state _Once_Lock( void )
0063 {
0064   Thread_Life_state thread_life_state;
0065
0066   thread_life_state = _Thread_Set_life_protection( THREAD_LIFE_PROTECTED );
0067   rtems_mutex_lock( &_Once_Information.Mutex );
0068
0069   return thread_life_state;
0070 }
0071
0072 static void _Once_Unlock( Thread_Life_state thread_life_state )
0073 {
0074   rtems_mutex_unlock( &_Once_Information.Mutex );
0075   _Thread_Set_life_protection( thread_life_state );
0076 }
0077
0078 int _Once( unsigned char *once_state, void ( *init_routine )( void ) )
0079 {
0080   _Atomic_Fence( ATOMIC_ORDER_ACQUIRE );
0081
0082   if ( RTEMS_PREDICT_FALSE( *once_state != ONCE_STATE_COMPLETE ) ) {
0083     Thread_Life_state thread_life_state;
0084
0085     thread_life_state = _Once_Lock();
0086
0087     if ( *once_state == ONCE_STATE_INIT ) {
0088       *once_state = ONCE_STATE_RUNNING;
0089       _Once_Unlock( THREAD_LIFE_PROTECTED );
0090       ( *init_routine )();
0091       _Once_Lock();
0092       _Atomic_Fence( ATOMIC_ORDER_RELEASE );
0093       *once_state = ONCE_STATE_COMPLETE;
0094       rtems_condition_variable_broadcast( &_Once_Information.State );
0095     } else {
0096       while ( *once_state != ONCE_STATE_COMPLETE ) {
0097         rtems_condition_variable_wait(
0098           &_Once_Information.State,
0099           &_Once_Information.Mutex
0100         );
0101       }
0102     }
0103
0104     _Once_Unlock( thread_life_state );
0105   }
0106
0107   return 0;
0108 }