250 lines
8.1 KiB
C
250 lines
8.1 KiB
C
/****************************************************************************
|
|
* include/semaphore.h
|
|
*
|
|
* Licensed to the Apache Software Foundation (ASF) under one or more
|
|
* contributor license agreements. See the NOTICE file distributed with
|
|
* this work for additional information regarding copyright ownership. The
|
|
* ASF licenses this file to you under the Apache License, Version 2.0 (the
|
|
* "License"); you may not use this file except in compliance with the
|
|
* License. You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
|
|
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
|
|
* License for the specific language governing permissions and limitations
|
|
* under the License.
|
|
*
|
|
****************************************************************************/
|
|
|
|
#ifndef __INCLUDE_SEMAPHORE_H
|
|
#define __INCLUDE_SEMAPHORE_H
|
|
|
|
/****************************************************************************
|
|
* Included Files
|
|
****************************************************************************/
|
|
|
|
#include <nuttx/config.h>
|
|
|
|
#include <stdint.h>
|
|
#include <limits.h>
|
|
#include <time.h>
|
|
#include <nuttx/queue.h>
|
|
|
|
/****************************************************************************
|
|
* Pre-processor Definitions
|
|
****************************************************************************/
|
|
|
|
/* Values for protocol attribute */
|
|
|
|
#define SEM_PRIO_NONE 0
|
|
#define SEM_PRIO_INHERIT 1
|
|
#define SEM_PRIO_PROTECT 2
|
|
#define SEM_PRIO_MASK 3
|
|
|
|
#define SEM_TYPE_MUTEX 4
|
|
|
|
/* Value returned by sem_open() in the event of a failure. */
|
|
|
|
#define SEM_FAILED NULL
|
|
|
|
/****************************************************************************
|
|
* Public Type Declarations
|
|
****************************************************************************/
|
|
|
|
/* This structure contains information about the holder of a semaphore */
|
|
|
|
#ifdef CONFIG_PRIORITY_INHERITANCE
|
|
struct tcb_s; /* Forward reference */
|
|
struct sem_s;
|
|
|
|
struct semholder_s
|
|
{
|
|
#if CONFIG_SEM_PREALLOCHOLDERS > 0
|
|
FAR struct semholder_s *flink; /* List of semaphore's holder */
|
|
#endif
|
|
FAR struct semholder_s *tlink; /* List of task held semaphores */
|
|
FAR struct sem_s *sem; /* Ths corresponding semaphore */
|
|
FAR struct tcb_s *htcb; /* Ths corresponding TCB */
|
|
int16_t counts; /* Number of counts owned by this holder */
|
|
};
|
|
|
|
#if CONFIG_SEM_PREALLOCHOLDERS > 0
|
|
# define SEMHOLDER_INITIALIZER {NULL, NULL, NULL, NULL, 0}
|
|
# define INITIALIZE_SEMHOLDER(h) \
|
|
do { \
|
|
(h)->flink = NULL; \
|
|
(h)->tlink = NULL; \
|
|
(h)->sem = NULL; \
|
|
(h)->htcb = NULL; \
|
|
(h)->counts = 0; \
|
|
} while (0)
|
|
#else
|
|
# define SEMHOLDER_INITIALIZER {NULL, NULL, NULL, 0}
|
|
# define INITIALIZE_SEMHOLDER(h) \
|
|
do { \
|
|
(h)->tlink = NULL; \
|
|
(h)->sem = NULL; \
|
|
(h)->htcb = NULL; \
|
|
(h)->counts = 0; \
|
|
} while (0)
|
|
#endif
|
|
#endif /* CONFIG_PRIORITY_INHERITANCE */
|
|
|
|
#define SEM_WAITLIST_INITIALIZER {NULL, NULL}
|
|
|
|
/* 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.
|
|
*/
|
|
|
|
uint8_t flags; /* See SEM_PRIO_* definitions */
|
|
|
|
dq_queue_t waitlist;
|
|
|
|
#ifdef CONFIG_PRIORITY_INHERITANCE
|
|
# if CONFIG_SEM_PREALLOCHOLDERS > 0
|
|
FAR struct semholder_s *hhead; /* List of holders of semaphore counts */
|
|
# else
|
|
struct semholder_s holder; /* Slot for old and new holder */
|
|
# endif
|
|
#endif
|
|
#ifdef CONFIG_PRIORITY_PROTECT
|
|
uint8_t ceiling; /* The priority ceiling owned by mutex */
|
|
uint8_t saved; /* The saved priority of thread before boost */
|
|
#endif
|
|
};
|
|
|
|
typedef struct sem_s sem_t;
|
|
|
|
/* Initializers */
|
|
|
|
#ifdef CONFIG_PRIORITY_INHERITANCE
|
|
# if CONFIG_SEM_PREALLOCHOLDERS > 0
|
|
/* semcount, flags, waitlist, hhead */
|
|
|
|
# define SEM_INITIALIZER(c) \
|
|
{(c), 0, SEM_WAITLIST_INITIALIZER, NULL}
|
|
# else
|
|
/* semcount, flags, waitlist, holder[2] */
|
|
|
|
# define SEM_INITIALIZER(c) \
|
|
{(c), 0, SEM_WAITLIST_INITIALIZER, SEMHOLDER_INITIALIZER}
|
|
# endif
|
|
#else
|
|
/* semcount, flags, waitlist */
|
|
|
|
# define SEM_INITIALIZER(c) \
|
|
{(c), 0, SEM_WAITLIST_INITIALIZER}
|
|
#endif
|
|
|
|
#define SEM_WAITLIST(sem) (&((sem)->waitlist))
|
|
|
|
/****************************************************************************
|
|
* Public Data
|
|
****************************************************************************/
|
|
|
|
#ifdef __cplusplus
|
|
#define EXTERN extern "C"
|
|
extern "C"
|
|
{
|
|
#else
|
|
#define EXTERN extern
|
|
#endif
|
|
|
|
/****************************************************************************
|
|
* Public Function Prototypes
|
|
****************************************************************************/
|
|
|
|
/* 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_clockwait(FAR sem_t *sem, clockid_t clockid,
|
|
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
|
|
|
|
/****************************************************************************
|
|
* Name: 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.
|
|
*
|
|
* Input Parameters:
|
|
* sem - A pointer to the semaphore whose attributes are to be
|
|
* modified
|
|
* protocol - The new protocol to use
|
|
*
|
|
* Returned Value:
|
|
* This function is exposed as a non-standard application interface. It
|
|
* returns zero (OK) if successful. Otherwise, -1 (ERROR) is returned and
|
|
* the errno value is set appropriately.
|
|
*
|
|
****************************************************************************/
|
|
|
|
int sem_setprotocol(FAR sem_t *sem, int protocol);
|
|
|
|
/****************************************************************************
|
|
* Name: sem_getprotocol
|
|
*
|
|
* Description:
|
|
* Return the value of the semaphore protocol attribute.
|
|
*
|
|
* Input 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.
|
|
*
|
|
* Returned Value:
|
|
* This function is exposed as a non-standard application interface. It
|
|
* returns zero (OK) if successful. Otherwise, -1 (ERROR) is returned and
|
|
* the errno value is set appropriately.
|
|
*
|
|
****************************************************************************/
|
|
|
|
int sem_getprotocol(FAR sem_t *sem, FAR int *protocol);
|
|
|
|
#undef EXTERN
|
|
#ifdef __cplusplus
|
|
}
|
|
#endif
|
|
|
|
#endif /* __INCLUDE_SEMAPHORE_H */
|