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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/>.
*/
/*
Concepts and parts of this file have been contributed by Leon Woestenberg.
*/
/**
* @file chcond.c
* @brief Condition Variables code.
*
* @addtogroup condvars 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 @p Mutex. Mutexes and CondVars
* together can implement a Monitor construct.
* @pre In order to use the condition variable APIs the @p CH_USE_CONDVARS
* option must be enabled in @p chconf.h.
* @{
*/
#include "ch.h"
#if (CH_USE_CONDVARS && CH_USE_MUTEXES) || defined(__DOXYGEN__)
/**
* @brief Initializes s @p CondVar structure.
*
* @param[out] cp pointer to a @p CondVar structure
*
* @init
*/
void chCondInit(CondVar *cp) {
chDbgCheck(cp != NULL, "chCondInit");
queue_init(&cp->c_queue);
}
/**
* @brief Signals one thread that is waiting on the condition variable.
*
* @param[in] cp pointer to the @p CondVar structure
*
* @api
*/
void chCondSignal(CondVar *cp) {
chDbgCheck(cp != NULL, "chCondSignal");
chSysLock();
if (notempty(&cp->c_queue))
chSchWakeupS(fifo_remove(&cp->c_queue), RDY_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 CondVar structure
*
* @iclass
*/
void chCondSignalI(CondVar *cp) {
chDbgCheck(cp != NULL, "chCondSignalI");
if (notempty(&cp->c_queue))
chSchReadyI(fifo_remove(&cp->c_queue))->p_u.rdymsg = RDY_OK;
}
/**
* @brief Signals all threads that are waiting on the condition variable.
*
* @param[in] cp pointer to the @p CondVar structure
*
* @api
*/
void chCondBroadcast(CondVar *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 CondVar structure
*
* @iclass
*/
void chCondBroadcastI(CondVar *cp) {
chDbgCheck(cp != NULL, "chCondBroadcastI");
/* Empties the condition variable queue and inserts all the Threads into the
ready list in FIFO order. The wakeup message is set to @p RDY_RESET in
order to make a chCondBroadcast() detectable from a chCondSignal().*/
while (cp->c_queue.p_next != (void *)&cp->c_queue)
chSchReadyI(fifo_remove(&cp->c_queue))->p_u.rdymsg = RDY_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 CondVar structure
* @return A message specifying how the invoking thread has been
* released from the condition variable.
* @retval RDY_OK if the condvar has been signaled using
* @p chCondSignal().
* @retval RDY_RESET if the condvar has been signaled using
* @p chCondBroadcast().
*
* @api
*/
msg_t chCondWait(CondVar *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 CondVar structure
* @return A message specifying how the invoking thread has been
* released from the condition variable.
* @retval RDY_OK if the condvar has been signaled using
* @p chCondSignal().
* @retval RDY_RESET if the condvar has been signaled using
* @p chCondBroadcast().
*
* @sclass
*/
msg_t chCondWaitS(CondVar *cp) {
Thread *ctp = currp;
Mutex *mp;
msg_t msg;
chDbgCheck(cp != NULL, "chCondWaitS");
chDbgAssert(ctp->p_mtxlist != NULL,
"chCondWaitS(), #1",
"not owning a mutex");
mp = chMtxUnlockS();
ctp->p_u.wtobjp = cp;
prio_insert(ctp, &cp->c_queue);
chSchGoSleepS(THD_STATE_WTCOND);
msg = ctp->p_u.rdymsg;
chMtxLockS(mp);
return msg;
}
#if CH_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_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 CondVar structure
* @param[in] time the number of ticks before the operation timeouts,
* the special value @p TIME_INFINITE is allowed.
* It is not possible to specify zero @p TIME_IMMEDIATE
* as timeout specification because it would make no sense
* in this function.
* @return A message specifying how the invoking thread has been
* released from the condition variable.
* @retval RDY_OK if the condvar has been signaled using
* @p chCondSignal().
* @retval RDY_RESET if the condvar has been signaled using
* @p chCondBroadcast().
* @retval RDY_TIMEOUT if the condvar has not been signaled within the
* specified timeout.
*
* @api
*/
msg_t chCondWaitTimeout(CondVar *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_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 CondVar structure
* @param[in] time the number of ticks before the operation timeouts,
* the special value @p TIME_INFINITE is allowed.
* It is not possible to specify zero @p TIME_IMMEDIATE
* as timeout specification because it would make no sense
* in this function.
* @return A message specifying how the invoking thread has been
* released from the condition variable.
* @retval RDY_OK if the condvar has been signaled using
* @p chCondSignal().
* @retval RDY_RESET if the condvar has been signaled using
* @p chCondBroadcast().
* @retval RDY_TIMEOUT if the condvar has not been signaled within the
* specified timeout.
*
* @sclass
*/
msg_t chCondWaitTimeoutS(CondVar *cp, systime_t time) {
Mutex *mp;
msg_t msg;
chDbgCheck(cp != NULL, "chCondWaitTimeoutS");
chDbgAssert(currp->p_mtxlist != NULL,
"chCondWaitTimeoutS(), #1",
"not owning a mutex");
mp = chMtxUnlockS();
currp->p_u.wtobjp = cp;
prio_insert(currp, &cp->c_queue);
msg = chSchGoSleepTimeoutS(THD_STATE_WTCOND, time);
if (msg != RDY_TIMEOUT)
chMtxLockS(mp);
return msg;
}
#endif /* CH_USE_CONDVARS_TIMEOUT */
#endif /* CH_USE_CONDVARS && CH_USE_MUTEXES */
/** @} */
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