177 lines
5.8 KiB
C
177 lines
5.8 KiB
C
/****************************************************************************
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* include/nuttx/rwsem.h
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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#ifndef __INCLUDE_NUTTX_RWSEM_H
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#define __INCLUDE_NUTTX_RWSEM_H
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/mutex.h>
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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#define RWSEM_NO_HOLDER ((pid_t)-1)
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#define RWSEM_INITIALIZER {NXMUTEX_INITIALIZER, SEM_INITIALIZER(0), \
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RWSEM_NO_HOLDER, 0, 0, 0}
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/****************************************************************************
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* Public Type Definitions
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****************************************************************************/
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typedef struct
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{
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mutex_t protected; /* Protecting Locks for Read/Write Locked Tables */
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sem_t waiting; /* Reader/writer Waiting queue */
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pid_t holder; /* The write lock holder, this lock still can be
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* locked when the holder is same as the current
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* task/thread.
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*/
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int waiter; /* Waiter Count */
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int writer; /* Writer Count */
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int reader; /* Reader Count */
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} rw_semaphore_t;
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/****************************************************************************
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* Public Function Prototypes
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****************************************************************************/
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/****************************************************************************
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* Name: down_read_trylock
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*
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* Description:
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* Acquire a read lock on a read-write-lock object.
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*
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* Input Parameters:
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* rwsem - Pointer to the read-write-lock descriptor.
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*
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* Returned Value:
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* Return 1 if successful, 0 if failed
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*
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****************************************************************************/
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int down_read_trylock(FAR rw_semaphore_t *rwsem);
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/****************************************************************************
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* Name: down_read
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*
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* Description:
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* Acquire a read lock on a read-write-lock object.
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*
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* Input Parameters:
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* rwsem - Pointer to the read-write-lock descriptor.
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*
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****************************************************************************/
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void down_read(FAR rw_semaphore_t *rwsem);
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/****************************************************************************
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* Name: up_read
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*
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* Description:
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* Unlock a read lock on a read-write-lock object.
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*
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* Input Parameters:
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* rwsem - Pointer to the read-write-lock descriptor.
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*
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****************************************************************************/
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void up_read(FAR rw_semaphore_t *rwsem);
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/****************************************************************************
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* Name: down_write_trylock
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*
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* Description:
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* Acquire a write lock on a read-write-lock object.
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*
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* Input Parameters:
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* rwsem - Pointer to the read-write-lock descriptor.
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*
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* Returned Value:
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* Return 1 if successful, 0 if failed
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*
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****************************************************************************/
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int down_write_trylock(FAR rw_semaphore_t *rwsem);
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/****************************************************************************
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* Name: down_write
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*
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* Description:
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* Acquire a write lock on a read-write-lock object.
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*
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* Input Parameters:
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* rwsem - Pointer to the read-write-lock descriptor.
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*
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****************************************************************************/
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void down_write(FAR rw_semaphore_t *rwsem);
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/****************************************************************************
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* Name: up_write
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*
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* Description:
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* Unlock a write lock on a read-write-lock object.
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*
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* Input Parameters:
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* rwsem - Pointer to the read-write-lock descriptor.
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*
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****************************************************************************/
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void up_write(FAR rw_semaphore_t *rwsem);
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/****************************************************************************
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* Name: init_rwsem
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*
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* Description:
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* Initialize a read-write-lock object, setting its initial state.
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*
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* Input Parameters:
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* rwsem - Pointer to the read-write-lock descriptor.
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*
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* Returned Value:
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* It follows the NuttX internal error return policy: Zero (OK) is
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* returned on success. A negated errno value is returned on failure.
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*
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****************************************************************************/
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int init_rwsem(FAR rw_semaphore_t *rwsem);
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/****************************************************************************
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* Name: destroy_rwsem
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*
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* Description:
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* Destroy a read-write-lock object, freeing any resources associated with
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* it.
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*
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* Input Parameters:
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* rwsem - Pointer to the read-write-lock descriptor.
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*
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****************************************************************************/
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void destroy_rwsem(FAR rw_semaphore_t *rwsem);
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#endif /* __INCLUDE_NUTTX_RWSEM_H */
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