2016-11-02 23:05:18 +08:00
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/****************************************************************************
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* sched/semaphore/sem_setprotocol.c
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*
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2017-10-04 05:35:24 +08:00
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* Copyright (C) 2016-2017 Gregory Nutt. All rights reserved.
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2016-11-02 23:05:18 +08:00
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* Author: Gregory Nutt <gnutt@nuttx.org>
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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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*
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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
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* 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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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <assert.h>
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#include <errno.h>
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2016-11-03 04:43:03 +08:00
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#include <nuttx/semaphore.h>
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2016-11-02 23:05:18 +08:00
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#include "semaphore/semaphore.h"
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2016-11-04 08:51:38 +08:00
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#ifdef CONFIG_PRIORITY_INHERITANCE
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2016-11-02 23:05:18 +08:00
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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2017-10-04 05:35:24 +08:00
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* Name: nxsem_setprotocol
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2016-11-02 23:05:18 +08:00
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*
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* Description:
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* Set semaphore protocol attribute.
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*
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2016-11-03 08:21:46 +08:00
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* One particularly important use of this furnction is when a semaphore
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* is used for inter-task communication like:
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*
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* TASK A TASK B
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2017-10-04 05:35:24 +08:00
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* nxsem_init(sem, 0, 0);
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* nxsem_wait(sem);
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* nxsem_post(sem);
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2016-11-03 08:21:46 +08:00
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* Awakens as holder
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*
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* In this case priority inheritance can interfere with the operation of
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* the semaphore. The problem is that when TASK A is restarted it is a
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2017-10-04 05:35:24 +08:00
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* holder of the semaphore. However, it never calls nxsem_post(sem) so it
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2016-11-03 08:21:46 +08:00
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* becomes *permanently* a holder of the semaphore and may have its
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* priority boosted when any other task tries to acquire the semaphore.
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*
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2017-10-04 05:35:24 +08:00
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* The fix is to call nxsem_setprotocol(SEM_PRIO_NONE) immediately after
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2016-11-03 08:21:46 +08:00
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* the sem_init() call so that there will be no priority inheritance
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* operations on this semaphore.
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*
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2018-03-13 23:52:27 +08:00
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* Input Parameters:
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2016-11-02 23:05:18 +08:00
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* sem - A pointer to the semaphore whose attributes are to be
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* modified
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* protocol - The new protocol to use
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*
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2018-02-02 00:00:02 +08:00
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* Returned Value:
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2017-10-04 05:35:24 +08:00
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* This is an internal OS interface and should not be used by applications.
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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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2016-11-02 23:05:18 +08:00
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*
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****************************************************************************/
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2017-10-04 05:35:24 +08:00
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int nxsem_setprotocol(FAR sem_t *sem, int protocol)
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2016-11-02 23:05:18 +08:00
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{
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DEBUGASSERT(sem != NULL);
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switch (protocol)
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{
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case SEM_PRIO_NONE:
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/* Disable priority inheritance */
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sem->flags |= PRIOINHERIT_FLAGS_DISABLE;
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/* Remove any current holders */
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2017-10-04 02:51:15 +08:00
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nxsem_destroyholder(sem);
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2016-11-02 23:05:18 +08:00
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return OK;
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case SEM_PRIO_INHERIT:
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/* Enable priority inheritance (dangerous) */
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sem->flags &= ~PRIOINHERIT_FLAGS_DISABLE;
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return OK;
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case SEM_PRIO_PROTECT:
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/* Not yet supported */
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2017-10-04 05:35:24 +08:00
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return -ENOSYS;
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2016-11-02 23:05:18 +08:00
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default:
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break;
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}
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2017-10-04 05:35:24 +08:00
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return -EINVAL;
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}
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/****************************************************************************
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* Name: sem_setprotocol
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*
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* Description:
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* Set semaphore protocol attribute.
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*
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* One particularly important use of this furnction is when a semaphore
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|
|
* is used for inter-task communication like:
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*
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* TASK A TASK B
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* sem_init(sem, 0, 0);
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2017-10-05 05:22:27 +08:00
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* nxsem_wait(sem);
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2017-10-04 05:35:24 +08:00
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* sem_post(sem);
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* Awakens as holder
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*
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* In this case priority inheritance can interfere with the operation of
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* the semaphore. The problem is that when TASK A is restarted it is a
|
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|
|
* holder of the semaphore. However, it never calls sem_post(sem) so it
|
|
|
|
* becomes *permanently* a holder of the semaphore and may have its
|
|
|
|
* priority boosted when any other task tries to acquire the semaphore.
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|
|
*
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|
|
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* The fix is to call sem_setprotocol(SEM_PRIO_NONE) immediately after
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* the sem_init() call so that there will be no priority inheritance
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|
|
* operations on this semaphore.
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*
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2018-03-13 23:52:27 +08:00
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* Input Parameters:
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2017-10-04 05:35:24 +08:00
|
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* sem - A pointer to the semaphore whose attributes are to be
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|
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* modified
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* protocol - The new protocol to use
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|
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*
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2018-02-02 00:00:02 +08:00
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* Returned Value:
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2017-10-04 05:35:24 +08:00
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* This function is exposed as a non-standard application interface. It
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* returns zero (OK) if successful. Otherwise, -1 (ERROR) is returned and
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* the errno value is set appropriately.
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*
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****************************************************************************/
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int sem_setprotocol(FAR sem_t *sem, int protocol)
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{
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int ret;
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ret = nxsem_setprotocol(sem, protocol);
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if (ret < 0)
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{
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set_errno(-ret);
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ret = ERROR;
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}
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return ret;
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2016-11-02 23:05:18 +08:00
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}
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2016-11-04 08:51:38 +08:00
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2016-11-04 11:27:52 +08:00
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#endif /* CONFIG_PRIORITY_INHERITANCE */
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