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/*
ChibiOS/RT - Copyright (C) 2006,2007,2008,2009,2010,
2011,2012,2013 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/>.
*/
/*
Concepts and parts of this file have been contributed by Leon Woestenberg.
*/
/**
* @file chcond.c
* @brief Condition Variables code.
*
* @addtogroup condition variables Condition Variables
* @details This module implements the Condition Variables mechanism. Condition
* variables are an extensions to the mutex subsystem and cannot
* work alone.
* <h2>Operation mode</h2>
* The condition variable is a synchronization object meant to be
* used inside a zone protected by a mutex. Mutexes and condition
* variables together can implement a Monitor construct.
* @pre In order to use the condition variable APIs the @p CH_CFG_USE_CONDVARS
* option must be enabled in @p chconf.h.
* @{
*/
#include "ch.h"
#if CH_CFG_USE_CONDVARS || defined(__DOXYGEN__)
/*===========================================================================*/
/* Module local definitions. */
/*===========================================================================*/
/*===========================================================================*/
/* Module exported variables. */
/*===========================================================================*/
/*===========================================================================*/
/* Module local types. */
/*===========================================================================*/
/*===========================================================================*/
/* Module local variables. */
/*===========================================================================*/
/*===========================================================================*/
/* Module local functions. */
/*===========================================================================*/
/*===========================================================================*/
/* Module exported functions. */
/*===========================================================================*/
/**
* @brief Initializes s @p condition_variable_t structure.
*
* @param[out] cp pointer to a @p condition_variable_t structure
*
* @init
*/
void chCondObjectInit(condition_variable_t *cp) {
chDbgCheck(cp != NULL);
queue_init(&cp->c_queue);
}
/**
* @brief Signals one thread that is waiting on the condition variable.
*
* @param[in] cp pointer to the @p condition_variable_t structure
*
* @api
*/
void chCondSignal(condition_variable_t *cp) {
chDbgCheck(cp != NULL);
chSysLock();
if (queue_notempty(&cp->c_queue))
chSchWakeupS(queue_fifo_remove(&cp->c_queue), MSG_OK);
chSysUnlock();
}
/**
* @brief Signals one thread that is waiting on the condition variable.
* @post This function does not reschedule so a call to a rescheduling
* function must be performed before unlocking the kernel. Note that
* interrupt handlers always reschedule on exit so an explicit
* reschedule must not be performed in ISRs.
*
* @param[in] cp pointer to the @p condition_variable_t structure
*
* @iclass
*/
void chCondSignalI(condition_variable_t *cp) {
chDbgCheckClassI();
chDbgCheck(cp != NULL);
if (queue_notempty(&cp->c_queue)) {
thread_t *tp = queue_fifo_remove(&cp->c_queue);
tp->p_u.rdymsg = MSG_OK;
chSchReadyI(tp);
}
}
/**
* @brief Signals all threads that are waiting on the condition variable.
*
* @param[in] cp pointer to the @p condition_variable_t structure
*
* @api
*/
void chCondBroadcast(condition_variable_t *cp) {
chSysLock();
chCondBroadcastI(cp);
chSchRescheduleS();
chSysUnlock();
}
/**
* @brief Signals all threads that are waiting on the condition variable.
* @post This function does not reschedule so a call to a rescheduling
* function must be performed before unlocking the kernel. Note that
* interrupt handlers always reschedule on exit so an explicit
* reschedule must not be performed in ISRs.
*
* @param[in] cp pointer to the @p condition_variable_t structure
*
* @iclass
*/
void chCondBroadcastI(condition_variable_t *cp) {
chDbgCheckClassI();
chDbgCheck(cp != NULL);
/* Empties the condition variable queue and inserts all the threads into the
ready list in FIFO order. The wakeup message is set to @p MSG_RESET in
order to make a chCondBroadcast() detectable from a chCondSignal().*/
while (cp->c_queue.p_next != (void *)&cp->c_queue)
chSchReadyI(queue_fifo_remove(&cp->c_queue))->p_u.rdymsg = MSG_RESET;
}
/**
* @brief Waits on the condition variable releasing the mutex lock.
* @details Releases the currently owned mutex, waits on the condition
* variable, and finally acquires the mutex again. All the sequence
* is performed atomically.
* @pre The invoking thread <b>must</b> have at least one owned mutex.
*
* @param[in] cp pointer to the @p condition_variable_t structure
* @return A message specifying how the invoking thread has been
* released from the condition variable.
* @retval MSG_OK if the condition variable has been signaled using
* @p chCondSignal().
* @retval MSG_RESET if the condition variable has been signaled using
* @p chCondBroadcast().
*
* @api
*/
msg_t chCondWait(condition_variable_t *cp) {
msg_t msg;
chSysLock();
msg = chCondWaitS(cp);
chSysUnlock();
return msg;
}
/**
* @brief Waits on the condition variable releasing the mutex lock.
* @details Releases the currently owned mutex, waits on the condition
* variable, and finally acquires the mutex again. All the sequence
* is performed atomically.
* @pre The invoking thread <b>must</b> have at least one owned mutex.
*
* @param[in] cp pointer to the @p condition_variable_t structure
* @return A message specifying how the invoking thread has been
* released from the condition variable.
* @retval MSG_OK if the condition variable has been signaled using
* @p chCondSignal().
* @retval MSG_RESET if the condition variable has been signaled using
* @p chCondBroadcast().
*
* @sclass
*/
msg_t chCondWaitS(condition_variable_t *cp) {
thread_t *ctp = currp;
mutex_t *mp;
msg_t msg;
chDbgCheckClassS();
chDbgCheck(cp != NULL);
chDbgAssert(ctp->p_mtxlist != NULL, "not owning a mutex");
mp = chMtxUnlockS();
ctp->p_u.wtobjp = cp;
queue_prio_insert(ctp, &cp->c_queue);
chSchGoSleepS(CH_STATE_WTCOND);
msg = ctp->p_u.rdymsg;
chMtxLockS(mp);
return msg;
}
#if CH_CFG_USE_CONDVARS_TIMEOUT || defined(__DOXYGEN__)
/**
* @brief Waits on the condition variable releasing the mutex lock.
* @details Releases the currently owned mutex, waits on the condition
* variable, and finally acquires the mutex again. All the sequence
* is performed atomically.
* @pre The invoking thread <b>must</b> have at least one owned mutex.
* @pre The configuration option @p CH_CFG_USE_CONDVARS_TIMEOUT must be enabled
* in order to use this function.
* @post Exiting the function because a timeout does not re-acquire the
* mutex, the mutex ownership is lost.
*
* @param[in] cp pointer to the @p condition_variable_t structure
* @param[in] time the number of ticks before the operation timeouts, the
* special values are handled as follow:
* - @a TIME_INFINITE no timeout.
* - @a TIME_IMMEDIATE this value is not allowed.
* .
* @return A message specifying how the invoking thread has been
* released from the condition variable.
* @retval MSG_OK if the condition variable has been signaled using
* @p chCondSignal().
* @retval MSG_RESET if the condition variable has been signaled using
* @p chCondBroadcast().
* @retval MSG_TIMEOUT if the condition variable has not been signaled within
* the specified timeout.
*
* @api
*/
msg_t chCondWaitTimeout(condition_variable_t *cp, systime_t time) {
msg_t msg;
chSysLock();
msg = chCondWaitTimeoutS(cp, time);
chSysUnlock();
return msg;
}
/**
* @brief Waits on the condition variable releasing the mutex lock.
* @details Releases the currently owned mutex, waits on the condition
* variable, and finally acquires the mutex again. All the sequence
* is performed atomically.
* @pre The invoking thread <b>must</b> have at least one owned mutex.
* @pre The configuration option @p CH_CFG_USE_CONDVARS_TIMEOUT must be enabled
* in order to use this function.
* @post Exiting the function because a timeout does not re-acquire the
* mutex, the mutex ownership is lost.
*
* @param[in] cp pointer to the @p condition_variable_t structure
* @param[in] time the number of ticks before the operation timeouts, the
* special values are handled as follow:
* - @a TIME_INFINITE no timeout.
* - @a TIME_IMMEDIATE this value is not allowed.
* .
* @return A message specifying how the invoking thread has been
* released from the condition variable.
* @retval MSG_OK if the condition variable has been signaled using
* @p chCondSignal().
* @retval MSG_RESET if the condition variable has been signaled using
* @p chCondBroadcast().
* @retval MSG_TIMEOUT if the condition variable has not been signaled within
* the specified timeout.
*
* @sclass
*/
msg_t chCondWaitTimeoutS(condition_variable_t *cp, systime_t time) {
mutex_t *mp;
msg_t msg;
chDbgCheckClassS();
chDbgCheck((cp != NULL) && (time != TIME_IMMEDIATE));
chDbgAssert(currp->p_mtxlist != NULL, "not owning a mutex");
mp = chMtxUnlockS();
currp->p_u.wtobjp = cp;
queue_prio_insert(currp, &cp->c_queue);
msg = chSchGoSleepTimeoutS(CH_STATE_WTCOND, time);
if (msg != MSG_TIMEOUT)
chMtxLockS(mp);
return msg;
}
#endif /* CH_CFG_USE_CONDVARS_TIMEOUT */
#endif /* CH_CFG_USE_CONDVARS */
/** @} */
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