tinySA/os/kernel/src/chcond.c

/*
    ChibiOS/RT - Copyright (C) 2006-2007 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 are contributed by and Copyright (C) 2008
   of Leon Woestenberg.
 */

/**
 * @file chcond.c
 * @brief Condition Variables code.
 * @addtogroup condvars Condition Variables
 * @{
 */

#include "ch.h"

#if CH_USE_CONDVARS && CH_USE_MUTEXES

/**
 * @brief Initializes s @p CondVar structure.
 *
 * @param[out] cp pointer to a @p CondVar structure
 * @note This function can be invoked from within an interrupt handler even if
 *       it is not an I-Class API because it does not touch any critical kernel
 *       data structure.
 */
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
 */
void chCondSignal(CondVar *cp) {

  chDbgCheck(cp != NULL, "chCondSignal");

  chSysLock();
  if (notempty(&cp->c_queue))                           /* any thread ? */
    chSchWakeupS(fifo_remove(&cp->c_queue), RDY_OK);
  chSysUnlock();
}

/**
 * @brief Signals one thread that is waiting on the condition variable.
 *
 * @param[in] cp pointer to the @p CondVar structure
 */
void chCondSignalI(CondVar *cp) {

  chDbgCheck(cp != NULL, "chCondSignalI");

  if (notempty(&cp->c_queue))                           /* any thread ? */
    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
 */
void chCondBroadcast(CondVar *cp) {

  chSysLock();
  chCondBroadcastI(cp);
  chSchRescheduleS();
  chSysUnlock();
}

/**
 * @brief Signals all threads that are waiting on the condition variable.
 *
 * @param[in] cp pointer to the @p CondVar structure
 */
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 mutex, waits on the condition variable, and finally
 *          acquires the mutex again. This is done atomically.
 *
 * @param[in] cp pointer to the @p CondVar structure
 * @return The wakep mode.
 * @retval RDY_OK if the condvar was signaled using chCondSignal().
 * @retval RDY_RESET if the condvar was signaled using chCondBroadcast().
 * @note  The thread MUST already have locked the mutex when calling
 *        @p chCondWait().
 */
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 mutex, waits on the condition variable, and finally
 *          acquires the mutex again. This is done atomically.
 *
 * @param[in] cp pointer to the @p CondVar structure
 * @return The wakep mode.
 * @retval RDY_OK if the condvar was signaled using chCondSignal().
 * @retval RDY_RESET if the condvar was signaled using chCondBroadcast().
 * @note  The thread MUST already have locked the mutex when calling
 *        @p chCondWaitS().
 */
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();
  prio_insert(ctp, &cp->c_queue);
  ctp->p_u.wtobjp = cp;
  chSchGoSleepS(THD_STATE_WTCOND);
  msg = ctp->p_u.rdymsg;
  chMtxLockS(mp);
  return msg;
}

#if CH_USE_CONDVARS_TIMEOUT
/**
 * @brief Waits on the condition variable releasing the mutex lock.
 * @details Releases the mutex, waits on the condition variable, and finally
 *          acquires the mutex again. This is done atomically.
 *
 * @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 The wakep mode.
 * @retval RDY_OK if the condvar was signaled using chCondSignal().
 * @retval RDY_RESET if the condvar was signaled using chCondBroadcast().
 * @retval RDY_TIMEOUT if the condvar was not signaled within the specified
 *         timeout.
 * @note  The thread MUST already have locked the mutex when calling
 *        @p chCondWaitTimeout().
 */
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 mutex, waits on the condition variable, and finally
 *          acquires the mutex again. This is done atomically.
 *
 * @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 The wakep mode.
 * @retval RDY_OK if the condvar was signaled using chCondSignal().
 * @retval RDY_RESET if the condvar was signaled using chCondBroadcast().
 * @retval RDY_TIMEOUT if the condvar was not signaled within the specified
 *         timeout.
 * @note  The thread MUST already have locked the mutex when calling
 *        @p chCondWaitTimeoutS().
 */
msg_t chCondWaitTimeoutS(CondVar *cp, systime_t time) {
  Thread *ctp = currp;
  Mutex *mp;
  msg_t msg;

  chDbgCheck(cp != NULL, "chCondWaitTimeoutS");
  chDbgAssert(ctp->p_mtxlist != NULL,
              "chCondWaitTimeoutS(), #1",
              "not owning a mutex");

  mp = chMtxUnlockS();
  prio_insert(ctp, &cp->c_queue);
  ctp->p_u.wtobjp = cp;
  chSchGoSleepTimeoutS(THD_STATE_WTCOND, time);
  msg = ctp->p_u.rdymsg;
  chMtxLockS(mp);
  return msg;
}
#endif /* CH_USE_CONDVARS_TIMEOUT */

#endif /* CH_USE_CONDVARS && CH_USE_MUTEXES */

/** @} */