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ChibiOS/os/rt/src/chschd.c

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/*
ChibiOS/RT - Copyright (C) 2006,2007,2008,2009,2010,
2011,2012,2013,2014 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 chschd.c
* @brief Scheduler code.
*
* @addtogroup scheduler
* @details This module provides the default portable scheduler code.
* @{
*/
#include "ch.h"
/*===========================================================================*/
/* Module local definitions. */
/*===========================================================================*/
/*===========================================================================*/
/* Module exported variables. */
/*===========================================================================*/
/**
* @brief System data structures.
*/
ch_system_t ch;
/*===========================================================================*/
/* Module local types. */
/*===========================================================================*/
/*===========================================================================*/
/* Module local variables. */
/*===========================================================================*/
/*===========================================================================*/
/* Module local functions. */
/*===========================================================================*/
/*===========================================================================*/
/* Module exported functions. */
/*===========================================================================*/
/**
* @brief Scheduler initialization.
*
* @notapi
*/
void _scheduler_init(void) {
queue_init(&ch.rlist.r_queue);
ch.rlist.r_prio = NOPRIO;
#if CH_CFG_USE_REGISTRY
ch.rlist.r_newer = ch.rlist.r_older = (thread_t *)&ch.rlist;
#endif
}
#if !CH_CFG_OPTIMIZE_SPEED || defined(__DOXYGEN__)
/**
* @brief Inserts a thread into a priority ordered queue.
* @note The insertion is done by scanning the list from the highest
* priority toward the lowest.
*
* @param[in] tp the pointer to the thread to be inserted in the list
* @param[in] tqp the pointer to the threads list header
*
* @notapi
*/
void queue_prio_insert(thread_t *tp, threads_queue_t *tqp) {
/* cp iterates over the queue.*/
thread_t *cp = (thread_t *)tqp;
do {
/* Iterate to next thread in queue.*/
cp = cp->p_next;
/* Not end of queue? and cp has equal or higher priority than tp?.*/
} while ((cp != (thread_t *)tqp) && (cp->p_prio >= tp->p_prio));
/* Insertion on p_prev.*/
tp->p_next = cp;
tp->p_prev = cp->p_prev;
tp->p_prev->p_next = cp->p_prev = tp;
}
/**
* @brief Inserts a thread into a queue.
*
* @param[in] tp the pointer to the thread to be inserted in the list
* @param[in] tqp the pointer to the threads list header
*
* @notapi
*/
void queue_insert(thread_t *tp, threads_queue_t *tqp) {
tp->p_next = (thread_t *)tqp;
tp->p_prev = tqp->p_prev;
tp->p_prev->p_next = tqp->p_prev = tp;
}
/**
* @brief Removes the first-out thread from a queue and returns it.
* @note If the queue is priority ordered then this function returns the
* thread with the highest priority.
*
* @param[in] tqp the pointer to the threads list header
* @return The removed thread pointer.
*
* @notapi
*/
thread_t *queue_fifo_remove(threads_queue_t *tqp) {
thread_t *tp = tqp->p_next;
(tqp->p_next = tp->p_next)->p_prev = (thread_t *)tqp;
return tp;
}
/**
* @brief Removes the last-out thread from a queue and returns it.
* @note If the queue is priority ordered then this function returns the
* thread with the lowest priority.
*
* @param[in] tqp the pointer to the threads list header
* @return The removed thread pointer.
*
* @notapi
*/
thread_t *queue_lifo_remove(threads_queue_t *tqp) {
thread_t *tp = tqp->p_prev;
(tqp->p_prev = tp->p_prev)->p_next = (thread_t *)tqp;
return tp;
}
/**
* @brief Removes a thread from a queue and returns it.
* @details The thread is removed from the queue regardless of its relative
* position and regardless the used insertion method.
*
* @param[in] tp the pointer to the thread to be removed from the queue
* @return The removed thread pointer.
*
* @notapi
*/
thread_t *queue_dequeue(thread_t *tp) {
tp->p_prev->p_next = tp->p_next;
tp->p_next->p_prev = tp->p_prev;
return tp;
}
/**
* @brief Pushes a thread_t on top of a stack list.
*
* @param[in] tp the pointer to the thread to be inserted in the list
* @param[in] tlp the pointer to the threads list header
*
* @notapi
*/
void list_insert(thread_t *tp, threads_list_t *tlp) {
tp->p_next = tlp->p_next;
tlp->p_next = tp;
}
/**
* @brief Pops a thread from the top of a stack list and returns it.
* @pre The list must be non-empty before calling this function.
*
* @param[in] tlp the pointer to the threads list header
* @return The removed thread pointer.
*
* @notapi
*/
thread_t *list_remove(threads_list_t *tlp) {
thread_t *tp = tlp->p_next;
tlp->p_next = tp->p_next;
return tp;
}
#endif /* CH_CFG_OPTIMIZE_SPEED */
/**
* @brief Inserts a thread in the Ready List.
* @details The thread is positioned behind all threads with higher or equal
* priority.
* @pre The thread must not be already inserted in any list through its
* @p p_next and @p p_prev or list corruption would occur.
* @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] tp the thread to be made ready
* @return The thread pointer.
*
* @iclass
*/
thread_t *chSchReadyI(thread_t *tp) {
thread_t *cp;
chDbgCheckClassI();
chDbgCheck(tp != NULL);
chDbgAssert((tp->p_state != CH_STATE_READY) &&
(tp->p_state != CH_STATE_FINAL),
"invalid state");
tp->p_state = CH_STATE_READY;
cp = (thread_t *)&ch.rlist.r_queue;
do {
cp = cp->p_next;
} while (cp->p_prio >= tp->p_prio);
/* Insertion on p_prev.*/
tp->p_next = cp;
tp->p_prev = cp->p_prev;
tp->p_prev->p_next = cp->p_prev = tp;
return tp;
}
/**
* @brief Puts the current thread to sleep into the specified state.
* @details The thread goes into a sleeping state. The possible
* @ref thread_states are defined into @p threads.h.
*
* @param[in] newstate the new thread state
*
* @sclass
*/
void chSchGoSleepS(tstate_t newstate) {
thread_t *otp;
chDbgCheckClassS();
(otp = currp)->p_state = newstate;
#if CH_CFG_TIME_QUANTUM > 0
/* The thread is renouncing its remaining time slices so it will have a new
time quantum when it will wakeup.*/
otp->p_preempt = CH_CFG_TIME_QUANTUM;
#endif
setcurrp(queue_fifo_remove(&ch.rlist.r_queue));
#if defined(CH_CFG_IDLE_ENTER_HOOK)
if (currp->p_prio == IDLEPRIO) {
CH_CFG_IDLE_ENTER_HOOK();
}
#endif
currp->p_state = CH_STATE_CURRENT;
chSysSwitch(currp, otp);
}
/*
* Timeout wakeup callback.
*/
static void wakeup(void *p) {
thread_t *tp = (thread_t *)p;
chSysLockFromISR();
switch (tp->p_state) {
case CH_STATE_READY:
/* Handling the special case where the thread has been made ready by
another thread with higher priority.*/
chSysUnlockFromISR();
return;
case CH_STATE_SUSPENDED:
*(thread_reference_t *)tp->p_u.wtobjp = NULL;
break;
#if CH_CFG_USE_SEMAPHORES
case CH_STATE_WTSEM:
chSemFastSignalI((semaphore_t *)tp->p_u.wtobjp);
/* Falls into, intentional. */
#endif
#if CH_CFG_USE_CONDVARS && CH_CFG_USE_CONDVARS_TIMEOUT
case CH_STATE_WTCOND:
#endif
case CH_STATE_QUEUED:
/* States requiring dequeuing.*/
queue_dequeue(tp);
}
tp->p_u.rdymsg = MSG_TIMEOUT;
chSchReadyI(tp);
chSysUnlockFromISR();
}
/**
* @brief Puts the current thread to sleep into the specified state with
* timeout specification.
* @details The thread goes into a sleeping state, if it is not awakened
* explicitly within the specified timeout then it is forcibly
* awakened with a @p MSG_TIMEOUT low level message. The possible
* @ref thread_states are defined into @p threads.h.
*
* @param[in] newstate the new thread state
* @param[in] time the number of ticks before the operation timeouts, the
* special values are handled as follow:
* - @a TIME_INFINITE the thread enters an infinite sleep
* state, this is equivalent to invoking
* @p chSchGoSleepS() but, of course, less efficient.
* - @a TIME_IMMEDIATE this value is not allowed.
* .
* @return The wakeup message.
* @retval MSG_TIMEOUT if a timeout occurs.
*
* @sclass
*/
msg_t chSchGoSleepTimeoutS(tstate_t newstate, systime_t time) {
chDbgCheckClassS();
if (TIME_INFINITE != time) {
virtual_timer_t vt;
chVTDoSetI(&vt, time, wakeup, currp);
chSchGoSleepS(newstate);
if (chVTIsArmedI(&vt))
chVTDoResetI(&vt);
}
else
chSchGoSleepS(newstate);
return currp->p_u.rdymsg;
}
/**
* @brief Wakes up a thread.
* @details The thread is inserted into the ready list or immediately made
* running depending on its relative priority compared to the current
* thread.
* @pre The thread must not be already inserted in any list through its
* @p p_next and @p p_prev or list corruption would occur.
* @note It is equivalent to a @p chSchReadyI() followed by a
* @p chSchRescheduleS() but much more efficient.
* @note The function assumes that the current thread has the highest
* priority.
*
* @param[in] ntp the thread to be made ready
* @param[in] msg the wakeup message
*
* @sclass
*/
void chSchWakeupS(thread_t *ntp, msg_t msg) {
chDbgCheckClassS();
/* Storing the message to be retrieved by the target thread when it will
restart execution.*/
ntp->p_u.rdymsg = msg;
/* If the waken thread has a not-greater priority than the current
one then it is just inserted in the ready list else it made
running immediately and the invoking thread goes in the ready
list instead.*/
if (ntp->p_prio <= currp->p_prio) {
chSchReadyI(ntp);
}
else {
thread_t *otp = chSchReadyI(currp);
setcurrp(ntp);
#if defined(CH_CFG_IDLE_LEAVE_HOOK)
if (otp->p_prio == IDLEPRIO) {
CH_CFG_IDLE_LEAVE_HOOK();
}
#endif
ntp->p_state = CH_STATE_CURRENT;
chSysSwitch(ntp, otp);
}
}
/**
* @brief Performs a reschedule if a higher priority thread is runnable.
* @details If a thread with a higher priority than the current thread is in
* the ready list then make the higher priority thread running.
*
* @sclass
*/
void chSchRescheduleS(void) {
chDbgCheckClassS();
if (chSchIsRescRequiredI())
chSchDoRescheduleAhead();
}
/**
* @brief Evaluates if preemption is required.
* @details The decision is taken by comparing the relative priorities and
* depending on the state of the round robin timeout counter.
* @note Not a user function, it is meant to be invoked by the scheduler
* itself or from within the port layer.
*
* @retval true if there is a thread that must go in running state
* immediately.
* @retval false if preemption is not required.
*
* @special
*/
bool chSchIsPreemptionRequired(void) {
tprio_t p1 = firstprio(&ch.rlist.r_queue);
tprio_t p2 = currp->p_prio;
#if CH_CFG_TIME_QUANTUM > 0
/* If the running thread has not reached its time quantum, reschedule only
if the first thread on the ready queue has a higher priority.
Otherwise, if the running thread has used up its time quantum, reschedule
if the first thread on the ready queue has equal or higher priority.*/
return currp->p_preempt ? p1 > p2 : p1 >= p2;
#else
/* If the round robin preemption feature is not enabled then performs a
simpler comparison.*/
return p1 > p2;
#endif
}
/**
* @brief Switches to the first thread on the runnable queue.
* @details The current thread is positioned in the ready list behind all
* threads having the same priority. The thread regains its time
* quantum.
* @note Not a user function, it is meant to be invoked by the scheduler
* itself or from within the port layer.
*
* @special
*/
void chSchDoRescheduleBehind(void) {
thread_t *otp;
otp = currp;
/* Picks the first thread from the ready queue and makes it current.*/
setcurrp(queue_fifo_remove(&ch.rlist.r_queue));
#if defined(CH_CFG_IDLE_LEAVE_HOOK)
if (otp->p_prio == IDLEPRIO) {
CH_CFG_IDLE_LEAVE_HOOK();
}
#endif
currp->p_state = CH_STATE_CURRENT;
#if CH_CFG_TIME_QUANTUM > 0
otp->p_preempt = CH_CFG_TIME_QUANTUM;
#endif
chSchReadyI(otp);
chSysSwitch(currp, otp);
}
/**
* @brief Switches to the first thread on the runnable queue.
* @details The current thread is positioned in the ready list ahead of all
* threads having the same priority.
* @note Not a user function, it is meant to be invoked by the scheduler
* itself or from within the port layer.
*
* @special
*/
void chSchDoRescheduleAhead(void) {
thread_t *otp, *cp;
otp = currp;
/* Picks the first thread from the ready queue and makes it current.*/
setcurrp(queue_fifo_remove(&ch.rlist.r_queue));
#if defined(CH_CFG_IDLE_LEAVE_HOOK)
if (otp->p_prio == IDLEPRIO) {
CH_CFG_IDLE_LEAVE_HOOK();
}
#endif
currp->p_state = CH_STATE_CURRENT;
otp->p_state = CH_STATE_READY;
cp = (thread_t *)&ch.rlist.r_queue;
do {
cp = cp->p_next;
} while (cp->p_prio > otp->p_prio);
/* Insertion on p_prev.*/
otp->p_next = cp;
otp->p_prev = cp->p_prev;
otp->p_prev->p_next = cp->p_prev = otp;
chSysSwitch(currp, otp);
}
/**
* @brief Switches to the first thread on the runnable queue.
* @details The current thread is positioned in the ready list behind or
* ahead of all threads having the same priority depending on
* if it used its whole time slice.
* @note Not a user function, it is meant to be invoked by the scheduler
* itself or from within the port layer.
*
* @special
*/
void chSchDoReschedule(void) {
#if CH_CFG_TIME_QUANTUM > 0
/* If CH_CFG_TIME_QUANTUM is enabled then there are two different scenarios
to handle on preemption: time quantum elapsed or not.*/
if (currp->p_preempt == 0) {
/* The thread consumed its time quantum so it is enqueued behind threads
with same priority level, however, it acquires a new time quantum.*/
chSchDoRescheduleBehind();
}
else {
/* The thread didn't consume all its time quantum so it is put ahead of
threads with equal priority and does not acquire a new time quantum.*/
chSchDoRescheduleAhead();
}
#else /* !(CH_CFG_TIME_QUANTUM > 0) */
/* If the round-robin mechanism is disabled then the thread goes always
ahead of its peers.*/
chSchDoRescheduleAhead();
#endif /* !(CH_CFG_TIME_QUANTUM > 0) */
}
/** @} */
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