247 lines
9.5 KiB
C
247 lines
9.5 KiB
C
/*
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ChibiOS/RT - Copyright (C) 2006,2007,2008,2009,2010,
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2011 Giovanni Di Sirio.
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This file is part of ChibiOS/RT.
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ChibiOS/RT is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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ChibiOS/RT is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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/**
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* @file chbsem.h
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* @brief Binary semaphores structures and macros.
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*
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* @addtogroup binary_semaphores
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* @details Binary semaphores related APIs and services.
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*
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* <h2>Operation mode</h2>
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* Binary semaphores are implemented as a set of macros that use the
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* existing counting semaphores primitives. The difference between
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* counting and binary semaphores is that the counter of binary
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* semaphores is not allowed to grow above the value 1. Repeated
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* signal operation are ignored. A binary semaphore can thus have
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* only two defined states:
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* - <b>Taken</b>, when its counter has a value of zero or lower
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* than zero. A negative number represent the number of threads
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* queued on the binary semaphore.
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* - <b>Not taken</b>, when its counter has a value of one.
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* .
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* Binary semaphores are different from mutexes because there is no
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* the concept of ownership, a binary semaphore can be taken by a
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* thread and signaled by another thread or an interrupt handler,
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* mutexes can only be taken and released by the same thread. Another
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* difference is that binary semaphores, unlike mutexes, do not
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* implement the priority inheritance protocol.<br>
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* In order to use the binary semaphores APIs the @p CH_USE_SEMAPHORES
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* option must be enabled in @p chconf.h.
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* @{
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*/
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#ifndef _CHBSEM_H_
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#define _CHBSEM_H_
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#if CH_USE_SEMAPHORES || defined(__DOXYGEN__)
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/**
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* @extends Semaphore
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*
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* @brief Binary semaphore type.
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*/
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typedef struct {
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Semaphore bs_sem;
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} BinarySemaphore;
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/**
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* @brief Data part of a static semaphore initializer.
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* @details This macro should be used when statically initializing a semaphore
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* that is part of a bigger structure.
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*
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* @param[in] name the name of the semaphore variable
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* @param[in] taken the semaphore initial state
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*/
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#define _BSEMAPHORE_DATA(name, taken) \
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{_SEMAPHORE_DATA(name.bs_sem, ((taken) ? 0 : 1))}
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/**
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* @brief Static semaphore initializer.
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* @details Statically initialized semaphores require no explicit
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* initialization using @p chSemInit().
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*
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* @param[in] name the name of the semaphore variable
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* @param[in] taken the semaphore initial state
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*/
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#define BSEMAPHORE_DECL(name, taken) \
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BinarySemaphore name = _BSEMAPHORE_DATA(name, taken)
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/**
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* @brief Initializes a binary semaphore.
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*
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* @param[out] bsp pointer to a @p BinarySemaphore structure
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* @param[in] taken initial state of the binary semaphore:
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* - @a FALSE, the initial state is not taken.
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* - @a TRUE, the initial state is taken.
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* .
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*
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* @init
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*/
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#define chBSemInit(bsp, taken) chSemInit(&(bsp)->bs_sem, (taken) ? 0 : 1)
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/**
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* @brief Wait operation on the binary semaphore.
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*
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* @param[in] bsp pointer to a @p BinarySemaphore structure
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* @return A message specifying how the invoking thread has been
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* released from the semaphore.
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* @retval RDY_OK if the binary semaphore has been successfully taken.
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* @retval RDY_RESET if the binary semaphore has been reset using
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* @p bsemReset().
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*
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* @api
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*/
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#define chBSemWait(bsp) chSemWait(&(bsp)->bs_sem)
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/**
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* @brief Wait operation on the binary semaphore.
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*
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* @param[in] bsp pointer to a @p BinarySemaphore structure
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* @return A message specifying how the invoking thread has been
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* released from the semaphore.
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* @retval RDY_OK if the binary semaphore has been successfully taken.
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* @retval RDY_RESET if the binary semaphore has been reset using
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* @p bsemReset().
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*
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* @sclass
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*/
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#define chBSemWaitS(bsp) chSemWaitS(&(bsp)->bs_sem)
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/**
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* @brief Wait operation on the binary semaphore.
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*
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* @param[in] bsp pointer to a @p BinarySemaphore structure
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* @param[in] time the number of ticks before the operation timeouts,
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* the following special values are allowed:
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* - @a TIME_IMMEDIATE immediate timeout.
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* - @a TIME_INFINITE no timeout.
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* .
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* @return A message specifying how the invoking thread has been
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* released from the semaphore.
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* @retval RDY_OK if the binary semaphore has been successfully taken.
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* @retval RDY_RESET if the binary semaphore has been reset using
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* @p bsemReset().
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* @retval RDY_TIMEOUT if the binary semaphore has not been signaled or reset
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* within the specified timeout.
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*
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* @api
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*/
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#define chBSemWaitTimeout(bsp, time) chSemWaitTimeout(&(bsp)->bs_sem, (time))
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/**
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* @brief Wait operation on the binary semaphore.
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*
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* @param[in] bsp pointer to a @p BinarySemaphore structure
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* @param[in] time the number of ticks before the operation timeouts,
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* the following special values are allowed:
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* - @a TIME_IMMEDIATE immediate timeout.
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* - @a TIME_INFINITE no timeout.
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* .
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* @return A message specifying how the invoking thread has been
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* released from the semaphore.
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* @retval RDY_OK if the binary semaphore has been successfully taken.
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* @retval RDY_RESET if the binary semaphore has been reset using
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* @p bsemReset().
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* @retval RDY_TIMEOUT if the binary semaphore has not been signaled or reset
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* within the specified timeout.
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*
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* @sclass
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*/
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#define chBSemWaitTimeoutS(bsp, time) chSemWaitTimeoutS(&(bsp)->bs_sem, (time))
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/**
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* @brief Reset operation on the binary semaphore.
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* @note The released threads can recognize they were waked up by a reset
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* rather than a signal because the @p bsemWait() will return
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* @p RDY_RESET instead of @p RDY_OK.
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*
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* @param[in] bsp pointer to a @p BinarySemaphore structure
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* @param[in] taken new state of the binary semaphore
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* - @a FALSE, the new state is not taken.
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* - @a TRUE, the new state is taken.
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* .
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*
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* @api
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*/
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#define chBSemReset(bsp, taken) chSemReset(&(bsp)->bs_sem, (taken) ? 0 : 1)
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/**
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* @brief Reset operation on the binary semaphore.
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* @note The released threads can recognize they were waked up by a reset
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* rather than a signal because the @p bsemWait() will return
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* @p RDY_RESET instead of @p RDY_OK.
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* @note This function does not reschedule.
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*
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* @param[in] bsp pointer to a @p BinarySemaphore structure
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* @param[in] taken new state of the binary semaphore
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* - @a FALSE, the new state is not taken.
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* - @a TRUE, the new state is taken.
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* .
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*
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* @iclass
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*/
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#define chBSemResetI(bsp, taken) chSemResetI(&(bsp)->bs_sem, (taken) ? 0 : 1)
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/**
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* @brief Performs a signal operation on a binary semaphore.
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*
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* @param[in] bsp pointer to a @p BinarySemaphore structure
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*
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* @api
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*/
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#define chBSemSignal(bsp) { \
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chSysLock(); \
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chBSemSignalI((bsp)); \
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chSchRescheduleS(); \
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chSysUnlock(); \
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}
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/**
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* @brief Performs a signal operation on a binary semaphore.
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* @note This function does not reschedule.
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*
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* @param[in] bsp pointer to a @p BinarySemaphore structure
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*
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* @iclass
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*/
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#define chBSemSignalI(bsp) { \
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if ((bsp)->bs_sem.s_cnt < 1) \
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chSemSignalI(&(bsp)->bs_sem); \
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}
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/**
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* @brief Returns the binary semaphore current state.
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*
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* @param[in] bsp pointer to a @p BinarySemaphore structure
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* @return The binary semaphore current state.
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* @retval FALSE if the binary semaphore is not taken.
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* @retval TRUE if the binary semaphore is taken.
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*
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* @iclass
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*/
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#define chBSemGetStateI(bsp) ((bsp)->bs_sem.s_cnt > 0 ? FALSE : TRUE)
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#endif /* CH_USE_SEMAPHORES */
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#endif /* _CHBSEM_H_ */
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/** @} */
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