210 lines
7.4 KiB
C
210 lines
7.4 KiB
C
/****************************************************************************
|
|
* include/nuttx/semaphore.h
|
|
*
|
|
* Copyright (C) 2014-2016 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.
|
|
*
|
|
****************************************************************************/
|
|
|
|
#ifndef __INCLUDE_NUTTX_SEMAPHORE_H
|
|
#define __INCLUDE_NUTTX_SEMAPHORE_H
|
|
|
|
/****************************************************************************
|
|
* Included Files
|
|
****************************************************************************/
|
|
|
|
#include <nuttx/config.h>
|
|
|
|
#include <semaphore.h>
|
|
|
|
#include <nuttx/clock.h>
|
|
#include <nuttx/fs/fs.h>
|
|
|
|
/****************************************************************************
|
|
* Pre-processor Definitions
|
|
****************************************************************************/
|
|
|
|
/* Values for protocol attribute */
|
|
|
|
#define SEM_PRIO_NONE 0
|
|
#define SEM_PRIO_INHERIT 1
|
|
#define SEM_PRIO_PROTECT 2
|
|
|
|
/****************************************************************************
|
|
* Public Type Definitions
|
|
****************************************************************************/
|
|
|
|
#ifdef CONFIG_FS_NAMED_SEMAPHORES
|
|
/* This is the named semaphore inode */
|
|
|
|
struct inode;
|
|
struct nsem_inode_s
|
|
{
|
|
/* This must be the first element of the structure. In sem_close() this
|
|
* structure must be cast compatible with sem_t.
|
|
*/
|
|
|
|
sem_t ns_sem; /* The contained semaphore */
|
|
|
|
/* Inode payload unique to named semaphores. */
|
|
|
|
FAR struct inode *ns_inode; /* Containing inode */
|
|
};
|
|
#endif
|
|
|
|
/****************************************************************************
|
|
* Public Data
|
|
****************************************************************************/
|
|
|
|
#ifndef __ASSEMBLY__
|
|
|
|
#ifdef __cplusplus
|
|
#define EXTERN extern "C"
|
|
extern "C"
|
|
{
|
|
#else
|
|
#define EXTERN extern
|
|
#endif
|
|
|
|
/****************************************************************************
|
|
* Public Function Prototypes
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Name: sem_tickwait
|
|
*
|
|
* Description:
|
|
* This function is a lighter weight version of sem_timedwait(). It is
|
|
* non-standard and intended only for use within the RTOS.
|
|
*
|
|
* Parameters:
|
|
* sem - Semaphore object
|
|
* start - The system time that the delay is relative to. If the
|
|
* current time is not the same as the start time, then the
|
|
* delay will be adjust so that the end time will be the same
|
|
* in any event.
|
|
* delay - Ticks to wait from the start time until the semaphore is
|
|
* posted. If ticks is zero, then this function is equivalent
|
|
* to sem_trywait().
|
|
*
|
|
* Return Value:
|
|
* Zero (OK) is returned on success. A negated errno value is returned on
|
|
* failure. -ETIMEDOUT is returned on the timeout condition.
|
|
*
|
|
****************************************************************************/
|
|
|
|
int sem_tickwait(FAR sem_t *sem, systime_t start, uint32_t delay);
|
|
|
|
/****************************************************************************
|
|
* Name: sem_reset
|
|
*
|
|
* Description:
|
|
* Reset a semaphore count to a specific value. This is similar to part
|
|
* of the operation of sem_init(). But sem_reset() may need to wake up
|
|
* tasks waiting on a count. This kind of operation is sometimes required
|
|
* within the OS (only) for certain error handling conditions.
|
|
*
|
|
* Parameters:
|
|
* sem - Semaphore descriptor to be reset
|
|
* count - The requested semaphore count
|
|
*
|
|
* Return Value:
|
|
* 0 (OK) or a negated errno value if unsuccessful
|
|
*
|
|
****************************************************************************/
|
|
|
|
int sem_reset(FAR sem_t *sem, int16_t count);
|
|
|
|
/****************************************************************************
|
|
* Function: sem_getprotocol
|
|
*
|
|
* Description:
|
|
* Return the value of the semaphore protocol attribute.
|
|
*
|
|
* Parameters:
|
|
* sem - A pointer to the semaphore whose attributes are to be
|
|
* queried.
|
|
* protocol - The user provided location in which to store the protocol
|
|
* value.
|
|
*
|
|
* Return Value:
|
|
* 0 if successful. Otherwise, -1 is returned and the errno value is set
|
|
* appropriately.
|
|
*
|
|
****************************************************************************/
|
|
|
|
int sem_getprotocol(FAR sem_t *sem, FAR int *protocol);
|
|
|
|
/****************************************************************************
|
|
* Function: sem_setprotocol
|
|
*
|
|
* Description:
|
|
* Set semaphore protocol attribute.
|
|
*
|
|
* One particularly important use of this function 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);
|
|
|
|
#undef EXTERN
|
|
#ifdef __cplusplus
|
|
}
|
|
#endif
|
|
|
|
#endif /* __ASSEMBLY__ */
|
|
#endif /* __INCLUDE_NUTTX_SEMAPHORE_H */
|