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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/>.
*/
/**
* @file chschd.c
* @brief Scheduler code.
*
* @addtogroup scheduler
* @{
*/
#include "ch.h"
/**
* @brief Ready list header.
*/
ReadyList rlist;
/**
* @brief Scheduler initialization.
* @note Internally invoked by the @p chSysInit(), not an API.
*/
void scheduler_init(void) {
queue_init(&rlist.r_queue);
rlist.r_prio = NOPRIO;
#if CH_TIME_QUANTUM > 0
rlist.r_preempt = CH_TIME_QUANTUM;
#endif
#if CH_USE_REGISTRY
rlist.p_newer = rlist.p_older = (Thread *)&rlist;
#endif
}
/**
* @brief Inserts a thread in the Ready List.
* @note The function does not reschedule, the @p chSchRescheduleS() should
* be called soon after.
*
* @param[in] tp the Thread to be made ready
* @return The Thread pointer.
*/
#if CH_OPTIMIZE_SPEED
/* NOTE: it is inlined in this module only.*/
INLINE Thread *chSchReadyI(Thread *tp) {
#else
Thread *chSchReadyI(Thread *tp) {
#endif
Thread *cp;
tp->p_state = THD_STATE_READY;
cp = (Thread *)&rlist.r_queue;
do {
cp = cp->p_next;
} while (cp->p_prio >= tp->p_prio);
/* Insertion on p_prev.*/
tp->p_prev = (tp->p_next = 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 @ref thread_states are
* described into @p threads.h.
*
* @param[in] newstate the new thread state
*/
void chSchGoSleepS(tstate_t newstate) {
Thread *otp;
(otp = currp)->p_state = newstate;
(currp = fifo_remove(&rlist.r_queue))->p_state = THD_STATE_CURRENT;
#if CH_TIME_QUANTUM > 0
rlist.r_preempt = CH_TIME_QUANTUM;
#endif
chDbgTrace(otp, currp);
chSysSwitchI(otp, currp);
}
/*
* Timeout wakeup callback.
*/
static void wakeup(void *p) {
Thread *tp = (Thread *)p;
#if CH_USE_SEMAPHORES || CH_USE_MUTEXES || CH_USE_CONDVARS
switch (tp->p_state) {
#if CH_USE_SEMAPHORES
case THD_STATE_WTSEM:
chSemFastSignalI((Semaphore *)tp->p_u.wtobjp);
/* Falls into, intentional. */
#endif
#if CH_USE_MUTEXES
case THD_STATE_WTMTX:
#endif
#if CH_USE_CONDVARS
case THD_STATE_WTCOND:
#endif
/* States requiring dequeuing.*/
dequeue(tp);
}
#endif
chSchReadyI(tp)->p_u.rdymsg = RDY_TIMEOUT;
}
/**
* @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 RDY_TIMEOUT low level message. The @ref
* thread_states are described 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 accepted but
* interpreted as a normal time specification not as an
* immediate timeout specification.
* .
* @return The wakeup message.
* @retval RDY_TIMEOUT if a timeout occurs.
*/
msg_t chSchGoSleepTimeoutS(tstate_t newstate, systime_t time) {
if (TIME_INFINITE != time) {
VirtualTimer vt;
chVTSetI(&vt, time, wakeup, currp);
chSchGoSleepS(newstate);
if (chVTIsArmedI(&vt))
chVTResetI(&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.
* @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 message to the awakened thread
*/
void chSchWakeupS(Thread *ntp, msg_t msg) {
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 *otp = currp;
chSchReadyI(otp);
#if CH_TIME_QUANTUM > 0
rlist.r_preempt = CH_TIME_QUANTUM;
#endif
(currp = ntp)->p_state = THD_STATE_CURRENT;
chDbgTrace(otp, ntp);
chSysSwitchI(otp, ntp);
}
}
/**
* @brief Switches to the first thread on the runnable queue.
* @note It is intended to be called if @p chSchRescRequiredI() evaluates
* to @p TRUE.
*/
void chSchDoRescheduleI(void) {
Thread *otp = currp;
/* Pick the first thread from the ready queue and makes it current.*/
(currp = fifo_remove(&rlist.r_queue))->p_state = THD_STATE_CURRENT;
chSchReadyI(otp);
#if CH_TIME_QUANTUM > 0
rlist.r_preempt = CH_TIME_QUANTUM;
#endif
chDbgTrace(otp, currp);
chSysSwitchI(otp, currp);
}
/**
* @brief Performs a reschedulation 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.
*/
void chSchRescheduleS(void) {
if (chSchIsRescRequiredI())
chSchDoRescheduleI();
}
/**
* @brief Evaluates if a reschedulation is required.
* @details The decision is taken by comparing the relative priorities and
* depending on the state of the round robin timeout counter.
* @note This function is meant to be used in the timer interrupt handler
* where @p chVTDoTickI() is invoked.
*
* @retval TRUE if there is a thread that should go in running state.
* @retval FALSE if a reschedulation is not required.
*/
bool_t chSchIsRescRequiredExI(void) {
tprio_t p1 = firstprio(&rlist.r_queue);
tprio_t p2 = currp->p_prio;
#if CH_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 rlist.r_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 Yields the time slot.
* @details Yields the CPU control to the next thread in the ready list with
* equal priority, if any.
*/
void chSchDoYieldS(void) {
if (chSchCanYieldS()) {
Thread *cp = (Thread *)&rlist.r_queue;
Thread *otp = currp;
/* Note, the following insertion code works because we know that on the
ready list there is at least one thread with priority equal or higher
than the current one.*/
otp->p_state = THD_STATE_READY;
do {
cp = cp->p_prev;
} while (cp->p_prio < otp->p_prio);
/* Insertion on p_next.*/
otp->p_next = (otp->p_prev = cp)->p_next;
otp->p_next->p_prev = cp->p_next = otp;
/* Pick the first thread from the ready queue and makes it current.*/
(currp = fifo_remove(&rlist.r_queue))->p_state = THD_STATE_CURRENT;
#if CH_TIME_QUANTUM > 0
rlist.r_preempt = CH_TIME_QUANTUM;
#endif
chDbgTrace(otp, currp);
chSysSwitchI(otp, currp);
}
}
/** @} */
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