/* ChibiOS/RT - Copyright (C) 2006,2007,2008,2009,2010 Giovanni Di Sirio. This file is part of ChibiOS/RT. ChibiOS/RT 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/RT 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 . */ /** * @file chbsem.h * @brief Binary semaphores structures and macros. * * @addtogroup binary_semaphores * @details Binary semaphores related APIs and services. * *

Operation mode

* Binary semaphores are implemented as a set of macros 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: * - Taken, 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. * - Not taken, when its counter has a value of one. * . * Binary semaphores are different from mutexes because there is no * the 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.
* In order to use the binary semaphores APIs the @p CH_USE_SEMAPHORES * option must be enabled in @p chconf.h. * @{ */ #ifndef _CHBSEM_H_ #define _CHBSEM_H_ #if CH_USE_SEMAPHORES /** * @extends Semaphore * * @brief Binary semaphore type. */ typedef struct { Semaphore bs_sem; } BinarySemaphore; /** * @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] n the counter initial value, this value must be * non-negative */ #define _BSEMAPHORE_DATA(name, t) {_SEMAPHORE_DATA(name.bs_sem), ((t) ? 0 : 1)} /** * @brief Static semaphore initializer. * @details Statically initialized semaphores require no explicit * initialization using @p chSemInit(). * * @param[in] name the name of the semaphore variable * @param[in] n the counter initial value, this value must be * non-negative */ #define BSEMAPHORE_DECL(name, t) Semaphore name = _BSEMAPHORE_DATA(name, t) /** * @brief Initializes a binary semaphore. * * @param[out] bsp pointer to a @p BinarySemaphore 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. * . */ #define chBSemInit(bsp, taken) chSemInit(&bsp->bs_sem, taken ? 0 : 1) /** * @brief Wait operation on the binary semaphore. * * @param[in] bsp pointer to a @p BinarySemaphore structure * @retval RDY_OK if the binary semaphore had been successfully taken. * @retval RDY_RESET if the binary semaphore has been reset using * @p bsemReset(). */ #define chBSemWait(bsp) chSemWait(&bsp->bs_sem) /** * @brief Wait operation on the binary semaphore. * * @param[in] bsp pointer to a @p BinarySemaphore structure * @retval RDY_OK if the binary semaphore had been successfully taken. * @retval RDY_RESET if the binary semaphore has been reset using * @p bsemReset(). */ #define chBSemWaitS(bsp) chSemWaitS(&bsp->bs_sem) /** * @brief Wait operation on the binary semaphore. * * @param[in] bsp pointer to a @p BinarySemaphore structure * @param[in] time the number of ticks before the operation timeouts, * the following special values are allowed: * - @a TIME_IMMEDIATE immediate timeout. * - @a TIME_INFINITE no timeout. * . * @retval RDY_OK if the binary semaphore had been successfully taken. * @retval RDY_RESET if the binary semaphore has been reset using * @p bsemReset(). * @retval RDY_TIMEOUT if the binary semaphore was not signaled or reset * within the specified timeout. */ #define chBSemWaitTimeout(bsp, time) chSemWaitTimeout(&bsp->bs_sem, time) /** * @brief Wait operation on the binary semaphore. * * @param[in] bsp pointer to a @p BinarySemaphore structure * @param[in] time the number of ticks before the operation timeouts, * the following special values are allowed: * - @a TIME_IMMEDIATE immediate timeout. * - @a TIME_INFINITE no timeout. * . * @retval RDY_OK if the binary semaphore had been successfully taken. * @retval RDY_RESET if the binary semaphore has been reset using * @p bsemReset(). * @retval RDY_TIMEOUT if the binary semaphore was not signaled or reset * within the specified timeout. */ #define chBSemWaitTimeoutS(bsp, time) chSemWaitTimeoutS(&bsp->bs_sem, time) /** * @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 RDY_RESET instead of @p RDY_OK. * * @param[in] bsp pointer to a @p BinarySemaphore 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. * . */ #define chBSemReset(bsp, taken) chSemReset(&bsp->bs_sem, taken ? 0 : 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 RDY_RESET instead of @p RDY_OK. * @note This function does not reschedule. * * @param[in] bsp pointer to a @p BinarySemaphore 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. * . */ #define chBSemResetI(bsp, taken) chSemResetI(&bsp->bs_sem, taken ? 0 : 1) /** * @brief Performs a signal operation on a binary semaphore. * * @param[in] bsp pointer to a @p BinarySemaphore structure */ #define chBSemSignal(bsp) { \ chSysLock(); \ chBSemSignalI(bsp); \ chSchRescheduleS(); \ chSysUnlock(); \ } /** * @brief Performs a signal operation on a binary semaphore. * @note This function does not reschedule. * * @param[in] bsp pointer to a @p BinarySemaphore structure */ #define chBSemSignalI(bsp) { \ if (bsp->bs_sem.s_cnt < 1) \ chSemSignalI(&bsp->bs_sem); \ } /** * @brief Returns the binary semaphore current state. * * @param[in] bsp pointer to a @p BinarySemaphore structure * @return The binary semaphore current state. * @retval FALSE if the binary semaphore is not taken. * @retval TRUE if the binary semaphore is taken. */ #define chBSemGetStateI(bsp) ((bsp)->bs_sem.s_cnt > 0 ? 0 : 1) #endif /* CH_USE_SEMAPHORES */ #endif /* _CHBSEM_H_ */ /** @} */