/*
ChibiOS - Copyright (C) 2006..2018 Giovanni Di Sirio.
This file is part of ChibiOS.
ChibiOS is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
ChibiOS is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* @file chbsem.h
* @brief Binary semaphores structures and macros.
*
* @addtogroup binary_semaphores
* @details Binary semaphores related APIs and services.
* <h2>Operation mode</h2>
* Binary semaphores are implemented as a set of inline functions
* that use the existing counting semaphores primitives. The
* difference between counting and binary semaphores is that the
* counter of binary semaphores is not allowed to grow above the
* value 1. Repeated signal operation are ignored. A binary
* semaphore can thus have only two defined states:
* - <b>Taken</b>, when its counter has a value of zero or lower
* than zero. A negative number represent the number of threads
* queued on the binary semaphore.
* - <b>Not taken</b>, when its counter has a value of one.
* .
* Binary semaphores are different from mutexes because there is no
* concept of ownership, a binary semaphore can be taken by a
* thread and signaled by another thread or an interrupt handler,
* mutexes can only be taken and released by the same thread. Another
* difference is that binary semaphores, unlike mutexes, do not
* implement the priority inheritance protocol.<br>
* In order to use the binary semaphores APIs the
* @p CH_CFG_USE_SEMAPHORES option must be enabled in @p chconf.h.
* @{
*/
#ifndef CHBSEM_H
#define CHBSEM_H
#if (CH_CFG_USE_SEMAPHORES == TRUE) || defined(__DOXYGEN__)
/*===========================================================================*/
/* Module constants. */
/*===========================================================================*/
/*===========================================================================*/
/* Module pre-compile time settings. */
/*===========================================================================*/
/*===========================================================================*/
/* Derived constants and error checks. */
/*===========================================================================*/
/*===========================================================================*/
/* Module data structures and types. */
/*===========================================================================*/
/**
* @extends semaphore_t
*
* @brief Binary semaphore type.
*/
typedef struct ch_binary_semaphore {
semaphore_t sem;
} binary_semaphore_t;
/*===========================================================================*/
/* Module macros. */
/*===========================================================================*/
/**
* @brief Data part of a static semaphore initializer.
* @details This macro should be used when statically initializing a semaphore
* that is part of a bigger structure.
*
* @param[in] name the name of the semaphore variable
* @param[in] taken the semaphore initial state
*/
#define _BSEMAPHORE_DATA(name, taken) \
{_SEMAPHORE_DATA(name.sem, ((taken) ? 0 : 1))}
/**
* @brief Static semaphore initializer.
* @details Statically initialized semaphores require no explicit
* initialization using @p chBSemInit().
*
* @param[in] name the name of the semaphore variable
* @param[in] taken the semaphore initial state
*/
#define BSEMAPHORE_DECL(name, taken) \
binary_semaphore_t name = _BSEMAPHORE_DATA(name, taken)
/*===========================================================================*/
/* External declarations. */
/*===========================================================================*/
/*===========================================================================*/
/* Module inline functions. */
/*===========================================================================*/
/**
* @brief Initializes a binary semaphore.
*
* @param[out] bsp pointer to a @p binary_semaphore_t structure
* @param[in] taken initial state of the binary semaphore:
* - @a false, the initial state is not taken.
* - @a true, the initial state is taken.
* .
*
* @init
*/
static inline void chBSemObjectInit(binary_semaphore_t *bsp, bool taken) {
chSemObjectInit(&bsp->sem, taken ? (cnt_t)0 : (cnt_t)1);
}
/**
* @brief Wait operation on the binary semaphore.
*
* @param[in] bsp pointer to a @p binary_semaphore_t structure
* @return A message specifying how the invoking thread has been
* released from the semaphore.
* @retval MSG_OK if the binary semaphore has been successfully taken.
* @retval MSG_RESET if the binary semaphore has been reset using
* @p bsemReset().
*
* @api
*/
static inline msg_t chBSemWait(binary_semaphore_t *bsp) {
return chSemWait(&bsp->sem);
}
/**
* @brief Wait operation on the binary semaphore.
*
* @param[in] bsp pointer to a @p binary_semaphore_t structure
* @return A message specifying how the invoking thread has been
* released from the semaphore.
* @retval MSG_OK if the binary semaphore has been successfully taken.
* @retval MSG_RESET if the binary semaphore has been reset using
* @p bsemReset().
*
* @sclass
*/
static inline msg_t chBSemWaitS(binary_semaphore_t *bsp) {
chDbgCheckClassS();
return chSemWaitS(&bsp->sem);
}
/**
* @brief Wait operation on the binary semaphore.
*
* @param[in] bsp pointer to a @p binary_semaphore_t structure
* @param[in] timeout the number of ticks before the operation timeouts,
* the following special values are allowed:
* - @a TIME_IMMEDIATE immediate timeout.
* - @a TIME_INFINITE no timeout.
* .
* @return A message specifying how the invoking thread has been
* released from the semaphore.
* @retval MSG_OK if the binary semaphore has been successfully taken.
* @retval MSG_RESET if the binary semaphore has been reset using
* @p bsemReset().
* @retval MSG_TIMEOUT if the binary semaphore has not been signaled or reset
* within the specified timeout.
*
* @sclass
*/
static inline msg_t chBSemWaitTimeoutS(binary_semaphore_t *bsp,
sysinterval_t timeout) {
chDbgCheckClassS();
return chSemWaitTimeoutS(&bsp->sem, timeout);
}
/**
* @brief Wait operation on the binary semaphore.
*
* @param[in] bsp pointer to a @p binary_semaphore_t structure
* @param[in] timeout the number of ticks before the operation timeouts,
* the following special values are allowed:
* - @a TIME_IMMEDIATE immediate timeout.
* - @a TIME_INFINITE no timeout.
* .
* @return A message specifying how the invoking thread has been
* released from the semaphore.
* @retval MSG_OK if the binary semaphore has been successfully taken.
* @retval MSG_RESET if the binary semaphore has been reset using
* @p bsemReset().
* @retval MSG_TIMEOUT if the binary semaphore has not been signaled or reset
* within the specified timeout.
*
* @api
*/
static inline msg_t chBSemWaitTimeout(binary_semaphore_t *bsp,
sysinterval_t timeout) {
return chSemWaitTimeout(&bsp->sem, timeout);
}
/**
* @brief Reset operation on the binary semaphore.
* @note The released threads can recognize they were waked up by a reset
* rather than a signal because the @p bsemWait() will return
* @p MSG_RESET instead of @p MSG_OK.
* @note This function does not reschedule.
*
* @param[in] bsp pointer to a @p binary_semaphore_t structure
* @param[in] taken new state of the binary semaphore
* - @a false, the new state is not taken.
* - @a true, the new state is taken.
* .
*
* @iclass
*/
static inline void chBSemResetI(binary_semaphore_t *bsp, bool taken) {
chDbgCheckClassI();
chSemResetI(&bsp->sem, taken ? (cnt_t)0 : (cnt_t)1);
}
/**
* @brief Reset operation on the binary semaphore.
* @note The released threads can recognize they were waked up by a reset
* rather than a signal because the @p bsemWait() will return
* @p MSG_RESET instead of @p MSG_OK.
*
* @param[in] bsp pointer to a @p binary_semaphore_t structure
* @param[in] taken new state of the binary semaphore
* - @a false, the new state is not taken.
* - @a true, the new state is taken.
* .
*
* @api
*/
static inline void chBSemReset(binary_semaphore_t *bsp, bool taken) {
chSemReset(&bsp->sem, taken ? (cnt_t)0 : (cnt_t)1);
}
/**
* @brief Performs a signal operation on a binary semaphore.
* @note This function does not reschedule.
*
* @param[in] bsp pointer to a @p binary_semaphore_t structure
*
* @iclass
*/
static inline void chBSemSignalI(binary_semaphore_t *bsp) {
chDbgCheckClassI();
if (bsp->sem.cnt < (cnt_t)1) {
chSemSignalI(&bsp->sem);
}
}
/**
* @brief Performs a signal operation on a binary semaphore.
*
* @param[in] bsp pointer to a @p binary_semaphore_t structure
*
* @api
*/
static inline void chBSemSignal(binary_semaphore_t *bsp) {
chSysLock();
chBSemSignalI(bsp);
chSchRescheduleS();
chSysUnlock();
}
/**
* @brief Returns the binary semaphore current state.
*
* @param[in] bsp pointer to a @p binary_semaphore_t structure
* @return The binary semaphore current state.
* @retval false if the binary semaphore is not taken.
* @retval true if the binary semaphore is taken.
*
* @iclass
*/
static inline bool chBSemGetStateI(binary_semaphore_t *bsp) {
chDbgCheckClassI();
return (bsp->sem.cnt > (cnt_t)0) ? false : true;
}
#endif /* CH_CFG_USE_SEMAPHORES == TRUE */
#endif /* CHBSEM_H */
/** @} */