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/*
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 <http://www.gnu.org/licenses/>.
*/
/**
* @file chsem.c
* @brief Semaphores code.
*
* @addtogroup semaphores
* @{
*/
#include "ch.h"
#if CH_USE_SEMAPHORES
#if CH_USE_SEMAPHORES_PRIORITY
#define sem_insert(tp, qp) prio_insert(tp, qp)
#else
#define sem_insert(tp, qp) queue_insert(tp, qp)
#endif
/**
* @brief Initializes a semaphore with the specified counter value.
*
* @param[out] sp pointer to a @p Semaphore structure
* @param[in] n initial value of the semaphore counter. Must be
* non-negative.
*/
void chSemInit(Semaphore *sp, cnt_t n) {
chDbgCheck((sp != NULL) && (n >= 0), "chSemInit");
queue_init(&sp->s_queue);
sp->s_cnt = n;
}
/**
* @brief Performs a reset operation on the semaphore.
* @note The released threads can recognize they were waked up by a reset
* rather than a signal because the @p chSemWait() will return
* @p RDY_RESET instead of @p RDY_OK.
*
* @param[in] sp pointer to a @p Semaphore structure
* @param[in] n the new value of the semaphore counter. The value must
* be non-negative.
*/
void chSemReset(Semaphore *sp, cnt_t n) {
chSysLock();
chSemResetI(sp, n);
chSchRescheduleS();
chSysUnlock();
}
/**
* @brief Performs a reset operation on the semaphore.
* @note The released threads can recognize they were waked up by a reset
* rather than a signal because the @p chSemWait() will return
* @p RDY_RESET instead of @p RDY_OK.
* @note This function does not reschedule.
*
* @param[in] sp pointer to a @p Semaphore structure
* @param[in] n the new value of the semaphore counter. The value must
* be non-negative.
*/
void chSemResetI(Semaphore *sp, cnt_t n) {
cnt_t cnt;
chDbgCheck((sp != NULL) && (n >= 0), "chSemResetI");
cnt = sp->s_cnt;
sp->s_cnt = n;
while (cnt++ < 0)
chSchReadyI(lifo_remove(&sp->s_queue))->p_u.rdymsg = RDY_RESET;
}
/**
* @brief Performs a wait operation on a semaphore.
*
* @param[in] sp pointer to a @p Semaphore structure
* @retval RDY_OK if the semaphore was signaled or not taken.
* @retval RDY_RESET if the semaphore was reset using @p chSemReset().
*/
msg_t chSemWait(Semaphore *sp) {
msg_t msg;
chSysLock();
msg = chSemWaitS(sp);
chSysUnlock();
return msg;
}
/**
* @brief Performs a wait operation on a semaphore.
*
* @param[in] sp pointer to a @p Semaphore structure
* @retval RDY_OK if the semaphore was signaled or not taken.
* @retval RDY_RESET if the semaphore was reset using @p chSemReset().
*/
msg_t chSemWaitS(Semaphore *sp) {
chDbgCheck(sp != NULL, "chSemWaitS");
if (--sp->s_cnt < 0) {
sem_insert(currp, &sp->s_queue);
currp->p_u.wtobjp = sp;
chSchGoSleepS(THD_STATE_WTSEM);
return currp->p_u.rdymsg;
}
return RDY_OK;
}
/**
* @brief Performs a wait operation on a semaphore with timeout specification.
*
* @param[in] sp pointer to a @p Semaphore 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 semaphore was signaled or not taken.
* @retval RDY_RESET if the semaphore was reset using @p chSemReset().
* @retval RDY_TIMEOUT if the semaphore was not signaled or reset within the
* specified timeout.
*/
msg_t chSemWaitTimeout(Semaphore *sp, systime_t time) {
msg_t msg;
chSysLock();
msg = chSemWaitTimeoutS(sp, time);
chSysUnlock();
return msg;
}
/**
* @brief Performs a wait operation on a semaphore with timeout specification.
*
* @param[in] sp pointer to a @p Semaphore 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 semaphore was signaled or not taken.
* @retval RDY_RESET if the semaphore was reset using @p chSemReset().
* @retval RDY_TIMEOUT if the semaphore was not signaled or reset within the
* specified timeout.
*/
msg_t chSemWaitTimeoutS(Semaphore *sp, systime_t time) {
chDbgCheck(sp != NULL, "chSemWaitTimeoutS");
if (--sp->s_cnt < 0) {
if (TIME_IMMEDIATE == time) {
sp->s_cnt++;
return RDY_TIMEOUT;
}
sem_insert(currp, &sp->s_queue);
currp->p_u.wtobjp = sp;
return chSchGoSleepTimeoutS(THD_STATE_WTSEM, time);
}
return RDY_OK;
}
/**
* @brief Performs a signal operation on a semaphore.
*
* @param[in] sp pointer to a @p Semaphore structure
*/
void chSemSignal(Semaphore *sp) {
chDbgCheck(sp != NULL, "chSemSignal");
chSysLock();
if (sp->s_cnt++ < 0)
chSchWakeupS(fifo_remove(&sp->s_queue), RDY_OK);
chSysUnlock();
}
/**
* @brief Performs a signal operation on a semaphore.
* @note This function does not reschedule.
*
* @param[in] sp pointer to a @p Semaphore structure
*/
void chSemSignalI(Semaphore *sp) {
chDbgCheck(sp != NULL, "chSemSignalI");
if (sp->s_cnt++ < 0) {
/* note, it is done this way in order to allow a tail call on
chSchReadyI().*/
Thread *tp = fifo_remove(&sp->s_queue);
tp->p_u.rdymsg = RDY_OK;
chSchReadyI(tp);
}
}
#if CH_USE_SEMSW
/**
* @brief Performs atomic signal and wait operations on two semaphores.
* @note The function is available only if the @p CH_USE_SEMSW
* option is enabled in @p chconf.h.
*
* @param[in] sps pointer to a @p Semaphore structure to be signaled
* @param[in] spw pointer to a @p Semaphore structure to be wait on
* @retval RDY_OK if the semaphore was signaled or not taken.
* @retval RDY_RESET if the semaphore was reset using @p chSemReset().
*/
msg_t chSemSignalWait(Semaphore *sps, Semaphore *spw) {
msg_t msg;
chDbgCheck((sps != NULL) && (spw != NULL), "chSemSignalWait");
chSysLock();
if (sps->s_cnt++ < 0)
chSchReadyI(fifo_remove(&sps->s_queue))->p_u.rdymsg = RDY_OK;
if (--spw->s_cnt < 0) {
sem_insert(currp, &spw->s_queue);
currp->p_u.wtobjp = spw;
chSchGoSleepS(THD_STATE_WTSEM);
msg = currp->p_u.rdymsg;
}
else {
chSchRescheduleS();
msg = RDY_OK;
}
chSysUnlock();
return msg;
}
#endif /* CH_USE_SEMSW */
#endif /* CH_USE_SEMAPHORES */
/** @} */
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