131 lines
4.3 KiB
C
131 lines
4.3 KiB
C
/****************************************************************************
|
|
* sched/semaphore/sem_setprotocol.c
|
|
*
|
|
* Copyright (C) 2016 Gregory Nutt. All rights reserved.
|
|
* Author: Gregory Nutt <gnutt@nuttx.org>
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
*
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* 2. Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in
|
|
* the documentation and/or other materials provided with the
|
|
* distribution.
|
|
* 3. Neither the name NuttX nor the names of its contributors may be
|
|
* used to endorse or promote products derived from this software
|
|
* without specific prior written permission.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
|
|
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
|
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
|
|
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
|
|
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
|
|
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
|
|
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
|
|
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
|
|
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
|
|
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
* POSSIBILITY OF SUCH DAMAGE.
|
|
*
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Included Files
|
|
****************************************************************************/
|
|
|
|
#include <nuttx/config.h>
|
|
|
|
#include <assert.h>
|
|
#include <errno.h>
|
|
|
|
#include <nuttx/semaphore.h>
|
|
|
|
#include "semaphore/semaphore.h"
|
|
|
|
#ifdef CONFIG_PRIORITY_INHERITANCE
|
|
|
|
/****************************************************************************
|
|
* Public Functions
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Function: sem_setprotocol
|
|
*
|
|
* Description:
|
|
* Set semaphore protocol attribute.
|
|
*
|
|
* One particularly important use of this furnction is when a semaphore
|
|
* is used for inter-task communication like:
|
|
*
|
|
* TASK A TASK B
|
|
* sem_init(sem, 0, 0);
|
|
* sem_wait(sem);
|
|
* sem_post(sem);
|
|
* Awakens as holder
|
|
*
|
|
* In this case priority inheritance can interfere with the operation of
|
|
* the semaphore. The problem is that when TASK A is restarted it is a
|
|
* 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.
|
|
*
|
|
* The fix is to call sem_setprotocol(SEM_PRIO_NONE) immediately after
|
|
* the sem_init() call so that there will be no priority inheritance
|
|
* operations on this semaphore.
|
|
*
|
|
* Parameters:
|
|
* sem - A pointer to the semaphore whose attributes are to be
|
|
* modified
|
|
* protocol - The new protocol to use
|
|
*
|
|
* Return Value:
|
|
* 0 if successful. Otherwise, -1 is returned and the errno value is set
|
|
* appropriately.
|
|
*
|
|
****************************************************************************/
|
|
|
|
int sem_setprotocol(FAR sem_t *sem, int protocol)
|
|
{
|
|
int errcode;
|
|
|
|
DEBUGASSERT(sem != NULL);
|
|
|
|
switch (protocol)
|
|
{
|
|
case SEM_PRIO_NONE:
|
|
/* Disable priority inheritance */
|
|
|
|
sem->flags |= PRIOINHERIT_FLAGS_DISABLE;
|
|
|
|
/* Remove any current holders */
|
|
|
|
sem_destroyholder(sem);
|
|
return OK;
|
|
|
|
case SEM_PRIO_INHERIT:
|
|
/* Enable priority inheritance (dangerous) */
|
|
|
|
sem->flags &= ~PRIOINHERIT_FLAGS_DISABLE;
|
|
return OK;
|
|
|
|
case SEM_PRIO_PROTECT:
|
|
/* Not yet supported */
|
|
|
|
errcode = ENOSYS;
|
|
break;
|
|
|
|
default:
|
|
errcode = EINVAL;
|
|
break;
|
|
}
|
|
|
|
set_errno(errcode);
|
|
return ERROR;
|
|
}
|
|
|
|
#endif /* CONFIG_PRIORITY_INHERITANCE */
|