402 lines
15 KiB
C
402 lines
15 KiB
C
/*
|
|
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/>.
|
|
*/
|
|
|
|
/**
|
|
* @file chsem.c
|
|
* @brief Semaphores code.
|
|
*
|
|
* @addtogroup semaphores
|
|
* @details Semaphores related APIs and services.
|
|
*
|
|
* <h2>Operation mode</h2>
|
|
* Semaphores are a flexible synchronization primitive, ChibiOS/RT
|
|
* implements semaphores in their "counting semaphores" variant as
|
|
* defined by Edsger Dijkstra plus several enhancements like:
|
|
* - Wait operation with timeout.
|
|
* - Reset operation.
|
|
* - Atomic wait+signal operation.
|
|
* - Return message from the wait operation (OK, RESET, TIMEOUT).
|
|
* .
|
|
* The binary semaphores variant can be easily implemented using
|
|
* counting semaphores.<br>
|
|
* Operations defined for semaphores:
|
|
* - <b>Signal</b>: The semaphore counter is increased and if the
|
|
* result is non-positive then a waiting thread is removed from
|
|
* the semaphore queue and made ready for execution.
|
|
* - <b>Wait</b>: The semaphore counter is decreased and if the result
|
|
* becomes negative the thread is queued in the semaphore and
|
|
* suspended.
|
|
* - <b>Reset</b>: The semaphore counter is reset to a non-negative
|
|
* value and all the threads in the queue are released.
|
|
* .
|
|
* Semaphores can be used as guards for mutual exclusion zones
|
|
* (note that mutexes are recommended for this kind of use) but
|
|
* also have other uses, queues guards and counters for example.<br>
|
|
* Semaphores usually use a FIFO queuing strategy but it is possible
|
|
* to make them order threads by priority by enabling
|
|
* @p CH_CFG_USE_SEMAPHORES_PRIORITY in @p chconf.h.
|
|
* @pre In order to use the semaphore APIs the @p CH_CFG_USE_SEMAPHORES
|
|
* option must be enabled in @p chconf.h.
|
|
* @{
|
|
*/
|
|
|
|
#include "ch.h"
|
|
|
|
#if CH_CFG_USE_SEMAPHORES || defined(__DOXYGEN__)
|
|
|
|
/*===========================================================================*/
|
|
/* Module exported variables. */
|
|
/*===========================================================================*/
|
|
|
|
/*===========================================================================*/
|
|
/* Module local types. */
|
|
/*===========================================================================*/
|
|
|
|
/*===========================================================================*/
|
|
/* Module local variables. */
|
|
/*===========================================================================*/
|
|
|
|
/*===========================================================================*/
|
|
/* Module local functions. */
|
|
/*===========================================================================*/
|
|
|
|
#if CH_CFG_USE_SEMAPHORES_PRIORITY
|
|
#define sem_insert(tp, qp) prio_insert(tp, qp)
|
|
#else
|
|
#define sem_insert(tp, qp) queue_insert(tp, qp)
|
|
#endif
|
|
|
|
/*===========================================================================*/
|
|
/* Module exported functions. */
|
|
/*===========================================================================*/
|
|
|
|
/**
|
|
* @brief Initializes a semaphore with the specified counter value.
|
|
*
|
|
* @param[out] sp pointer to a @p semaphore_t structure
|
|
* @param[in] n initial value of the semaphore counter. Must be
|
|
* non-negative.
|
|
*
|
|
* @init
|
|
*/
|
|
void chSemObjectInit(semaphore_t *sp, cnt_t n) {
|
|
|
|
chDbgCheck((sp != NULL) && (n >= 0));
|
|
|
|
queue_init(&sp->s_queue);
|
|
sp->s_cnt = n;
|
|
}
|
|
|
|
/**
|
|
* @brief Performs a reset operation on the semaphore.
|
|
* @post After invoking this function all the threads waiting on the
|
|
* semaphore, if any, are released and the semaphore counter is set
|
|
* to the specified, non negative, value.
|
|
* @note The released threads can recognize they were waked up by a reset
|
|
* rather than a signal because the @p chSemWait() will return
|
|
* @p MSG_RESET instead of @p MSG_OK.
|
|
*
|
|
* @param[in] sp pointer to a @p semaphore_t structure
|
|
* @param[in] n the new value of the semaphore counter. The value must
|
|
* be non-negative.
|
|
*
|
|
* @api
|
|
*/
|
|
void chSemReset(semaphore_t *sp, cnt_t n) {
|
|
|
|
chSysLock();
|
|
chSemResetI(sp, n);
|
|
chSchRescheduleS();
|
|
chSysUnlock();
|
|
}
|
|
|
|
/**
|
|
* @brief Performs a reset operation on the semaphore.
|
|
* @post After invoking this function all the threads waiting on the
|
|
* semaphore, if any, are released and the semaphore counter is set
|
|
* to the specified, non negative, value.
|
|
* @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.
|
|
* @note The released threads can recognize they were waked up by a reset
|
|
* rather than a signal because the @p chSemWait() will return
|
|
* @p MSG_RESET instead of @p MSG_OK.
|
|
*
|
|
* @param[in] sp pointer to a @p semaphore_t structure
|
|
* @param[in] n the new value of the semaphore counter. The value must
|
|
* be non-negative.
|
|
*
|
|
* @iclass
|
|
*/
|
|
void chSemResetI(semaphore_t *sp, cnt_t n) {
|
|
cnt_t cnt;
|
|
|
|
chDbgCheckClassI();
|
|
chDbgCheck((sp != NULL) && (n >= 0));
|
|
chDbgAssert(((sp->s_cnt >= 0) && queue_isempty(&sp->s_queue)) ||
|
|
((sp->s_cnt < 0) && queue_notempty(&sp->s_queue)),
|
|
"inconsistent semaphore");
|
|
|
|
cnt = sp->s_cnt;
|
|
sp->s_cnt = n;
|
|
while (++cnt <= 0)
|
|
chSchReadyI(queue_lifo_remove(&sp->s_queue))->p_u.rdymsg = MSG_RESET;
|
|
}
|
|
|
|
/**
|
|
* @brief Performs a wait operation on a semaphore.
|
|
*
|
|
* @param[in] sp pointer to a @p semaphore_t structure
|
|
* @return A message specifying how the invoking thread has been
|
|
* released from the semaphore.
|
|
* @retval MSG_OK if the thread has not stopped on the semaphore or the
|
|
* semaphore has been signaled.
|
|
* @retval MSG_RESET if the semaphore has been reset using @p chSemReset().
|
|
*
|
|
* @api
|
|
*/
|
|
msg_t chSemWait(semaphore_t *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_t structure
|
|
* @return A message specifying how the invoking thread has been
|
|
* released from the semaphore.
|
|
* @retval MSG_OK if the thread has not stopped on the semaphore or the
|
|
* semaphore has been signaled.
|
|
* @retval MSG_RESET if the semaphore has been reset using @p chSemReset().
|
|
*
|
|
* @sclass
|
|
*/
|
|
msg_t chSemWaitS(semaphore_t *sp) {
|
|
|
|
chDbgCheckClassS();
|
|
chDbgCheck(sp != NULL);
|
|
chDbgAssert(((sp->s_cnt >= 0) && queue_isempty(&sp->s_queue)) ||
|
|
((sp->s_cnt < 0) && queue_notempty(&sp->s_queue)),
|
|
"inconsistent semaphore");
|
|
|
|
if (--sp->s_cnt < 0) {
|
|
currp->p_u.wtobjp = sp;
|
|
sem_insert(currp, &sp->s_queue);
|
|
chSchGoSleepS(CH_STATE_WTSEM);
|
|
return currp->p_u.rdymsg;
|
|
}
|
|
return MSG_OK;
|
|
}
|
|
|
|
/**
|
|
* @brief Performs a wait operation on a semaphore with timeout specification.
|
|
*
|
|
* @param[in] sp pointer to a @p semaphore_t 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.
|
|
* .
|
|
* @return A message specifying how the invoking thread has been
|
|
* released from the semaphore.
|
|
* @retval MSG_OK if the thread has not stopped on the semaphore or the
|
|
* semaphore has been signaled.
|
|
* @retval MSG_RESET if the semaphore has been reset using @p chSemReset().
|
|
* @retval MSG_TIMEOUT if the semaphore has not been signaled or reset within
|
|
* the specified timeout.
|
|
*
|
|
* @api
|
|
*/
|
|
msg_t chSemWaitTimeout(semaphore_t *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_t 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.
|
|
* .
|
|
* @return A message specifying how the invoking thread has been
|
|
* released from the semaphore.
|
|
* @retval MSG_OK if the thread has not stopped on the semaphore or the
|
|
* semaphore has been signaled.
|
|
* @retval MSG_RESET if the semaphore has been reset using @p chSemReset().
|
|
* @retval MSG_TIMEOUT if the semaphore has not been signaled or reset within
|
|
* the specified timeout.
|
|
*
|
|
* @sclass
|
|
*/
|
|
msg_t chSemWaitTimeoutS(semaphore_t *sp, systime_t time) {
|
|
|
|
chDbgCheckClassS();
|
|
chDbgCheck(sp != NULL);
|
|
chDbgAssert(((sp->s_cnt >= 0) && queue_isempty(&sp->s_queue)) ||
|
|
((sp->s_cnt < 0) && queue_notempty(&sp->s_queue)),
|
|
"inconsistent semaphore");
|
|
|
|
if (--sp->s_cnt < 0) {
|
|
if (TIME_IMMEDIATE == time) {
|
|
sp->s_cnt++;
|
|
return MSG_TIMEOUT;
|
|
}
|
|
currp->p_u.wtobjp = sp;
|
|
sem_insert(currp, &sp->s_queue);
|
|
return chSchGoSleepTimeoutS(CH_STATE_WTSEM, time);
|
|
}
|
|
return MSG_OK;
|
|
}
|
|
|
|
/**
|
|
* @brief Performs a signal operation on a semaphore.
|
|
*
|
|
* @param[in] sp pointer to a @p semaphore_t structure
|
|
*
|
|
* @api
|
|
*/
|
|
void chSemSignal(semaphore_t *sp) {
|
|
|
|
chDbgCheck(sp != NULL);
|
|
chDbgAssert(((sp->s_cnt >= 0) && queue_isempty(&sp->s_queue)) ||
|
|
((sp->s_cnt < 0) && queue_notempty(&sp->s_queue)),
|
|
"inconsistent semaphore");
|
|
|
|
chSysLock();
|
|
if (++sp->s_cnt <= 0)
|
|
chSchWakeupS(queue_fifo_remove(&sp->s_queue), MSG_OK);
|
|
chSysUnlock();
|
|
}
|
|
|
|
/**
|
|
* @brief Performs a signal operation on a semaphore.
|
|
* @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] sp pointer to a @p semaphore_t structure
|
|
*
|
|
* @iclass
|
|
*/
|
|
void chSemSignalI(semaphore_t *sp) {
|
|
|
|
chDbgCheckClassI();
|
|
chDbgCheck(sp != NULL);
|
|
chDbgAssert(((sp->s_cnt >= 0) && queue_isempty(&sp->s_queue)) ||
|
|
((sp->s_cnt < 0) && queue_notempty(&sp->s_queue)),
|
|
"inconsistent semaphore");
|
|
|
|
if (++sp->s_cnt <= 0) {
|
|
/* Note, it is done this way in order to allow a tail call on
|
|
chSchReadyI().*/
|
|
thread_t *tp = queue_fifo_remove(&sp->s_queue);
|
|
tp->p_u.rdymsg = MSG_OK;
|
|
chSchReadyI(tp);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* @brief Adds the specified value to the semaphore counter.
|
|
* @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] sp pointer to a @p semaphore_t structure
|
|
* @param[in] n value to be added to the semaphore counter. The value
|
|
* must be positive.
|
|
*
|
|
* @iclass
|
|
*/
|
|
void chSemAddCounterI(semaphore_t *sp, cnt_t n) {
|
|
|
|
chDbgCheckClassI();
|
|
chDbgCheck((sp != NULL) && (n > 0));
|
|
chDbgAssert(((sp->s_cnt >= 0) && queue_isempty(&sp->s_queue)) ||
|
|
((sp->s_cnt < 0) && queue_notempty(&sp->s_queue)),
|
|
"inconsistent semaphore");
|
|
|
|
while (n > 0) {
|
|
if (++sp->s_cnt <= 0)
|
|
chSchReadyI(queue_fifo_remove(&sp->s_queue))->p_u.rdymsg = MSG_OK;
|
|
n--;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* @brief Performs atomic signal and wait operations on two semaphores.
|
|
*
|
|
* @param[in] sps pointer to a @p semaphore_t structure to be signaled
|
|
* @param[in] spw pointer to a @p semaphore_t structure to wait on
|
|
* @return A message specifying how the invoking thread has been
|
|
* released from the semaphore.
|
|
* @retval MSG_OK if the thread has not stopped on the semaphore or the
|
|
* semaphore has been signaled.
|
|
* @retval MSG_RESET if the semaphore has been reset using @p chSemReset().
|
|
*
|
|
* @api
|
|
*/
|
|
msg_t chSemSignalWait(semaphore_t *sps, semaphore_t *spw) {
|
|
msg_t msg;
|
|
|
|
chDbgCheck((sps != NULL) && (spw != NULL));
|
|
chDbgAssert(((sps->s_cnt >= 0) && queue_isempty(&sps->s_queue)) ||
|
|
((sps->s_cnt < 0) && queue_notempty(&sps->s_queue)),
|
|
"inconsistent semaphore");
|
|
chDbgAssert(((spw->s_cnt >= 0) && queue_isempty(&spw->s_queue)) ||
|
|
((spw->s_cnt < 0) && queue_notempty(&spw->s_queue)),
|
|
"inconsistent semaphore");
|
|
|
|
chSysLock();
|
|
if (++sps->s_cnt <= 0)
|
|
chSchReadyI(queue_fifo_remove(&sps->s_queue))->p_u.rdymsg = MSG_OK;
|
|
if (--spw->s_cnt < 0) {
|
|
thread_t *ctp = currp;
|
|
sem_insert(ctp, &spw->s_queue);
|
|
ctp->p_u.wtobjp = spw;
|
|
chSchGoSleepS(CH_STATE_WTSEM);
|
|
msg = ctp->p_u.rdymsg;
|
|
}
|
|
else {
|
|
chSchRescheduleS();
|
|
msg = MSG_OK;
|
|
}
|
|
chSysUnlock();
|
|
return msg;
|
|
}
|
|
|
|
#endif /* CH_CFG_USE_SEMAPHORES */
|
|
|
|
/** @} */
|