forked from Imagelibrary/rtems
146 lines
4.4 KiB
C
146 lines
4.4 KiB
C
/* SPDX-License-Identifier: BSD-2-Clause */
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/**
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* @file
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*
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* @ingroup RTEMSScoreRWLock
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*
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* @brief This source file contains the implementation of
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* _CORE_RWLock_Surrender().
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*/
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/*
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* COPYRIGHT (c) 1989-2006.
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* On-Line Applications Research Corporation (OAR).
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include <rtems/score/corerwlockimpl.h>
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#include <rtems/score/assert.h>
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static bool _CORE_RWLock_Is_waiting_for_reading(
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const Thread_Control *the_thread
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)
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{
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if ( the_thread->Wait.option == CORE_RWLOCK_THREAD_WAITING_FOR_READ ) {
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return true;
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} else {
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_Assert( the_thread->Wait.option == CORE_RWLOCK_THREAD_WAITING_FOR_WRITE );
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return false;
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}
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}
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static Thread_Control *_CORE_RWLock_Flush_filter(
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Thread_Control *the_thread,
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Thread_queue_Queue *queue,
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Thread_queue_Context *queue_context
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)
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{
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CORE_RWLock_Control *the_rwlock;
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the_rwlock = RTEMS_CONTAINER_OF(
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queue,
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CORE_RWLock_Control,
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Queue.Queue
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);
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switch ( the_rwlock->current_state ) {
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case CORE_RWLOCK_LOCKED_FOR_READING:
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if ( _CORE_RWLock_Is_waiting_for_reading( the_thread ) ) {
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the_rwlock->number_of_readers += 1;
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} else {
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the_thread = NULL;
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}
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break;
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case CORE_RWLOCK_LOCKED_FOR_WRITING:
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the_thread = NULL;
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break;
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default:
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_Assert( the_rwlock->current_state == CORE_RWLOCK_UNLOCKED );
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if ( _CORE_RWLock_Is_waiting_for_reading( the_thread ) ) {
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the_rwlock->current_state = CORE_RWLOCK_LOCKED_FOR_READING;
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the_rwlock->number_of_readers = 1;
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} else {
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the_rwlock->current_state = CORE_RWLOCK_LOCKED_FOR_WRITING;
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}
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break;
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}
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return the_thread;
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}
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Status_Control _CORE_RWLock_Surrender( CORE_RWLock_Control *the_rwlock )
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{
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Thread_queue_Context queue_context;
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/*
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* If unlocked, then OK to read.
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* Otherwise, we have to block.
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* If locked for reading and no waiters, then OK to read.
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* If any thread is waiting, then we wait.
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*/
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_Thread_queue_Context_initialize( &queue_context );
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_CORE_RWLock_Acquire( the_rwlock, &queue_context );
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if ( the_rwlock->current_state == CORE_RWLOCK_UNLOCKED){
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/* This is an error at the caller site */
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_CORE_RWLock_Release( the_rwlock, &queue_context );
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return STATUS_SUCCESSFUL;
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}
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if ( the_rwlock->current_state == CORE_RWLOCK_LOCKED_FOR_READING ) {
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the_rwlock->number_of_readers -= 1;
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if ( the_rwlock->number_of_readers != 0 ) {
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/* must be unlocked again */
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_CORE_RWLock_Release( the_rwlock, &queue_context );
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return STATUS_SUCCESSFUL;
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}
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}
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_Assert(
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the_rwlock->current_state == CORE_RWLOCK_LOCKED_FOR_WRITING
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|| ( the_rwlock->current_state == CORE_RWLOCK_LOCKED_FOR_READING
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&& the_rwlock->number_of_readers == 0 )
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);
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/*
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* Implicitly transition to "unlocked" and find another thread interested
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* in obtaining this rwlock.
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*/
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the_rwlock->current_state = CORE_RWLOCK_UNLOCKED;
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_Thread_queue_Flush_critical(
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&the_rwlock->Queue.Queue,
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CORE_RWLOCK_TQ_OPERATIONS,
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_CORE_RWLock_Flush_filter,
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&queue_context
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);
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return STATUS_SUCCESSFUL;
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}
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