230 lines
6.7 KiB
C
230 lines
6.7 KiB
C
/*
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ChibiOS/RT - Copyright (C) 2006-2007 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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* @addtogroup Semaphores
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* @{
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*/
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#include <ch.h>
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#ifdef CH_USE_SEMAPHORES
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/**
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* Initializes a semaphore with the specified counter value.
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* @param sp pointer to a \p Semaphore structure
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* @param n initial value of the semaphore counter. Must be non-negative.
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* @note Can be called with interrupts disabled or enabled.
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*/
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void chSemInit(Semaphore *sp, cnt_t n) {
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chDbgAssert(n >= 0, "chsem.c, chSemInit()");
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fifo_init(&sp->s_queue);
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sp->s_cnt = n;
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}
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/**
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* Performs a reset operation on the semaphore.
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* @param sp pointer to a \p Semaphore structure
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* @param n the new value of the semaphore counter. The value must be non-negative.
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* @note The released threads can recognize they were waked up by a reset
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* instead than a signal because the \p chSemWait() will return
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* \p RDY_RESET instead of \p RDY_OK.
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*/
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void chSemReset(Semaphore *sp, cnt_t n) {
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chSysLock();
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chSemResetI(sp, n);
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chSchRescheduleS();
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chSysUnlock();
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}
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/**
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* Performs a reset operation on the semaphore.
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* @param sp pointer to a \p Semaphore structure
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* @param n the new value of the semaphore counter. The value must be non-negative.
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* @note The released threads can recognize they were waked up by a reset
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* instead than a signal because the \p chSemWait() 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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void chSemResetI(Semaphore *sp, cnt_t n) {
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cnt_t cnt;
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chDbgAssert(n >= 0, "chsem.c, chSemResetI()");
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cnt = sp->s_cnt;
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sp->s_cnt = n;
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while (cnt++ < 0)
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chSchReadyI(lifo_remove(&sp->s_queue))->p_rdymsg = RDY_RESET;
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}
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/**
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* Performs a wait operation on a semaphore.
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* @param sp pointer to a \p Semaphore structure
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* @retval RDY_OK if the semaphore was signaled or not taken.
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* @retval RDY_RESET if the semaphore was reset using \p chSemReset().
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*/
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msg_t chSemWait(Semaphore *sp) {
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msg_t msg;
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chSysLock();
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msg = chSemWaitS(sp);
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chSysUnlock();
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return msg;
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}
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/**
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* Performs a wait operation on a semaphore.
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* @param sp pointer to a \p Semaphore structure
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* @retval RDY_OK if the semaphore was signaled or not taken.
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* @retval RDY_RESET if the semaphore was reset using \p chSemReset().
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* @note This function must be called with interrupts disabled.
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* @note This function cannot be called by an interrupt handler.
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*/
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msg_t chSemWaitS(Semaphore *sp) {
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if (--sp->s_cnt < 0) {
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queue_insert(currp, &sp->s_queue);
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currp->p_wtsemp = sp;
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chSchGoSleepS(PRWTSEM);
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return currp->p_rdymsg;
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}
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return RDY_OK;
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}
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#ifdef CH_USE_SEMAPHORES_TIMEOUT
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/**
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* Performs a wait operation on a semaphore with timeout specification.
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* @param sp pointer to a \p Semaphore structure
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* @param time the number of ticks before the operation fails
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* @retval RDY_OK if the semaphore was signaled or not taken.
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* @retval RDY_RESET if the semaphore was reset using \p chSemReset().
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* @retval RDY_TIMEOUT if the semaphore was not signaled or reset within the specified
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* timeout.
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* @note The function is available only if the \p CH_USE_SEMAPHORES_TIMEOUT
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* option is enabled in \p chconf.h.
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*/
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msg_t chSemWaitTimeout(Semaphore *sp, systime_t time) {
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msg_t msg;
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chSysLock();
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msg = chSemWaitTimeoutS(sp, time);
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chSysUnlock();
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return msg;
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}
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/**
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* Performs a wait operation on a semaphore with timeout specification.
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* @param sp pointer to a \p Semaphore structure
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* @param time the number of ticks before the operation fails
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* @retval RDY_OK if the semaphore was signaled or not taken.
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* @retval RDY_RESET if the semaphore was reset using \p chSemReset().
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* @retval RDY_TIMEOUT if the semaphore was not signaled or reset within the specified
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* timeout.
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* @note The function is available only if the \p CH_USE_SEMAPHORES_TIMEOUT
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* option is enabled in \p chconf.h.
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*/
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msg_t chSemWaitTimeoutS(Semaphore *sp, systime_t time) {
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if (--sp->s_cnt < 0) {
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queue_insert(currp, &sp->s_queue);
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currp->p_wtsemp = sp;
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return chSchGoSleepTimeoutS(PRWTSEM, time);
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}
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return RDY_OK;
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}
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#endif /* CH_USE_SEMAPHORES_TIMEOUT */
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/**
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* Performs a signal operation on a semaphore.
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* @param sp pointer to a \p Semaphore structure
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* @note The function is available only if the \p CH_USE_SEMAPHORES
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* option is enabled in \p chconf.h.
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*/
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void chSemSignal(Semaphore *sp) {
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chSysLock();
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if (sp->s_cnt++ < 0)
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chSchWakeupS(fifo_remove(&sp->s_queue), RDY_OK);
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chSysUnlock();
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}
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/**
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* Performs a signal operation on a semaphore.
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* @param sp pointer to a \p Semaphore structure
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* @note The function is available only if the \p CH_USE_SEMAPHORES
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* option is enabled in \p chconf.h.
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* @note This function does not reschedule.
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*/
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void chSemSignalI(Semaphore *sp) {
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if (sp->s_cnt++ < 0) {
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/* NOTE: It is done this way in order to allow a tail call on
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chSchReadyI().*/
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Thread *tp = fifo_remove(&sp->s_queue);
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tp->p_rdymsg = RDY_OK;
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chSchReadyI(tp);
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}
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}
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#ifdef CH_USE_SEMSW
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/**
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* Performs atomic signal and wait operations on two semaphores.
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* @param sps pointer to a \p Semaphore structure to be signaled
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* @param spw pointer to a \p Semaphore structure to be wait on
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* @retval RDY_OK if the semaphore was signaled or not taken.
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* @retval RDY_RESET if the semaphore was reset using \p chSemReset().
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* @note The function is available only if the \p CH_USE_SEMSW
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* option is enabled in \p chconf.h.
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*/
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msg_t chSemSignalWait(Semaphore *sps, Semaphore *spw) {
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msg_t msg;
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chSysLock();
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if (sps->s_cnt++ < 0)
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chSchReadyI(fifo_remove(&sps->s_queue))->p_rdymsg = RDY_OK;
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if (--spw->s_cnt < 0) {
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queue_insert(currp, &spw->s_queue);
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currp->p_wtsemp = spw;
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chSchGoSleepS(PRWTSEM);
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msg = currp->p_rdymsg;
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}
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else {
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chSchRescheduleS();
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msg = RDY_OK;
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}
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chSysUnlock();
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return msg;
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}
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#endif /* CH_USE_SEMSW */
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#endif /* CH_USE_SEMAPHORES */
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/** @} */
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