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/****************************************************************************
* include/semaphore.h
*
* Copyright (C) 2007-2009, 2012-2013 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_SEMAPHORE_H
#define __INCLUDE_SEMAPHORE_H
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <stdint.h>
#include <limits.h>
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* Value returned by sem_open() in the event of a failure. */
#define SEM_FAILED ((FAR sem_t *)NULL)
/* Bit definitions for the struct sem_s flags field */
#define PRIOINHERIT_FLAGS_DISABLE (1 << 0) /* Bit 0: Priority inheritance
* is disabled for this semaphore. */
/****************************************************************************
* Public Type Declarations
****************************************************************************/
/* This structure contains information about the holder of a semaphore */
#ifdef CONFIG_PRIORITY_INHERITANCE
struct tcb_s; /* Forward reference */
struct semholder_s
{
#if CONFIG_SEM_PREALLOCHOLDERS > 0
struct semholder_s *flink; /* Implements singly linked list */
#endif
FAR struct tcb_s *htcb; /* Holder TCB */
int16_t counts; /* Number of counts owned by this holder */
};
#if CONFIG_SEM_PREALLOCHOLDERS > 0
# define SEMHOLDER_INITIALIZER {NULL, NULL, 0}
#else
# define SEMHOLDER_INITIALIZER {NULL, 0}
#endif
#endif /* CONFIG_PRIORITY_INHERITANCE */
/* This is the generic semaphore structure. */
struct sem_s
{
volatile int16_t semcount; /* >0 -> Num counts available */
/* <0 -> Num tasks waiting for semaphore */
/* If priority inheritance is enabled, then we have to keep track of which
* tasks hold references to the semaphore.
*/
#ifdef CONFIG_PRIORITY_INHERITANCE
uint8_t flags; /* See PRIOINHERIT_FLAGS_* definitions */
# if CONFIG_SEM_PREALLOCHOLDERS > 0
FAR struct semholder_s *hhead; /* List of holders of semaphore counts */
# else
struct semholder_s holder[2]; /* Slot for old and new holder */
# endif
#endif
};
typedef struct sem_s sem_t;
/* Initializers */
#ifdef CONFIG_PRIORITY_INHERITANCE
# if CONFIG_SEM_PREALLOCHOLDERS > 0
# define SEM_INITIALIZER(c) \
{(c), 0, NULL} /* semcount, flags, hhead */
# else
# define SEM_INITIALIZER(c) \
{(c), 0, {SEMHOLDER_INITIALIZER, SEMHOLDER_INITIALIZER}} /* semcount, flags, holder[2] */
# endif
#else
# define SEM_INITIALIZER(c) \
{(c)} /* semcount */
#endif
/****************************************************************************
* Public Data
****************************************************************************/
#ifdef __cplusplus
#define EXTERN extern "C"
extern "C"
{
#else
#define EXTERN extern
#endif
/****************************************************************************
* Public Function Prototypes
****************************************************************************/
/* Forward references needed by some prototypes */
struct timespec; /* Defined in time.h */
/* Counting Semaphore Interfaces (based on POSIX APIs) */
int sem_init(FAR sem_t *sem, int pshared, unsigned int value);
int sem_destroy(FAR sem_t *sem);
int sem_wait(FAR sem_t *sem);
int sem_timedwait(FAR sem_t *sem, FAR const struct timespec *abstime);
int sem_trywait(FAR sem_t *sem);
int sem_post(FAR sem_t *sem);
int sem_getvalue(FAR sem_t *sem, FAR int *sval);
#ifdef CONFIG_FS_NAMED_SEMAPHORES
FAR sem_t *sem_open(FAR const char *name, int oflag, ...);
int sem_close(FAR sem_t *sem);
int sem_unlink(FAR const char *name);
#endif
#undef EXTERN
#ifdef __cplusplus
}
#endif
#endif /* __INCLUDE_SEMAPHORE_H */