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/*
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/>.
*/
/**
* @addtogroup Scheduler
* @{
*/
#include <ch.h>
/** @cond never*/
static ReadyList rlist;
#ifndef CH_CURRP_REGISTER_CACHE
Thread *currp;
#endif
static UWORD16 preempt;
#ifdef CH_USE_SYSTEMTIME
t_time stime;
#endif
/** @endcond */
/**
* Scheduler initialization.
* @note Internally invoked by the \p chSysInit().
*/
void chSchInit(void) {
rlist.p_next = rlist.p_prev = (Thread *)&rlist;
rlist.p_prio = MAXPRIO;
preempt = CH_TIME_QUANTUM;
#ifdef CH_USE_SYSTEMTIME
stime = 0;
#endif
}
/**
* Inserts a thread in the Ready List.
* @param tp the Thread to be made ready
* @return the Thread pointer
* @note The function must be called in the system mutex zone.
* @note The function does not reschedule, the \p chSchRescheduleI() should
* be called soon after.
* @note The function is not meant to be used in the user code directly.
*/
Thread *chSchReadyI(Thread *tp) {
Thread *cp;
t_prio prio = tp->p_prio;
tp->p_state = PRREADY;
tp->p_rdymsg = RDY_OK;
cp = rlist.p_next;
while (cp->p_prio < prio)
cp = cp->p_next;
tp->p_prev = (tp->p_next = cp)->p_prev;
tp->p_prev->p_next = cp->p_prev = tp;
return tp;
}
/*
* Switches to the next thread in the ready list, the ready list is assumed
* to contain at least a thread.
*/
static void nextready(void) {
Thread *otp = currp;
(currp = dequeue(rlist.p_prev))->p_state = PRCURR;
preempt = CH_TIME_QUANTUM;
chSysSwitchI(&otp->p_ctx, &currp->p_ctx);
}
/**
* Puts the current thread to sleep into the specified state, the next highest
* priority thread becomes running. The threads states are described into
* \p threads.h
* @param newstate the new thread state
* @return the wakeup message
* @note The function must be called in the system mutex zone.
* @note The function is not meant to be used in the user code directly.
*/
void chSchGoSleepI(t_tstate newstate) {
currp->p_state = newstate;
nextready();
}
/**
* Wakeups a thread, the thread is inserted into the ready list or made
* running directly depending on its relative priority compared to the current
* thread.
* @param tp the Thread to be made ready
* @param msg wakeup message to the awakened thread
* @note The function must be called in the system mutex zone.
* @note The function is not meant to be used in the user code directly.
* @note It is equivalent to a \p chSchReadyI() followed by a
* \p chSchRescheduleI() but much more efficient.
*/
void chSchWakeupI(Thread *tp, t_msg msg) {
Thread *ctp = currp;
if (tp->p_prio <= ctp->p_prio)
chSchReadyI(tp)->p_rdymsg = msg;
else {
chSchReadyI(ctp);
(currp = tp)->p_state = PRCURR;
tp->p_rdymsg = msg;
preempt = CH_TIME_QUANTUM;
chSysSwitchI(&ctp->p_ctx, &tp->p_ctx);
}
}
/**
* If a thread with an higher priority than the current thread is in the
* ready list then it becomes running.
* @note The function must be called in the system mutex zone.
*/
void chSchRescheduleI(void) {
if (isempty(&rlist) || lastprio(&rlist) <= currp->p_prio)
return;
chSchDoRescheduleI();
}
/**
* Performs a reschedulation. It is meant to be called if
* \p chSchRescRequired() evaluates to \p TRUE.
*/
void chSchDoRescheduleI(void) {
chSchReadyI(currp);
nextready();
}
/**
* Evaluates if a reschedulation is required.
* @return \p TRUE if there is a thread that should go in running state
* immediatly else \p FALSE.
*/
BOOL chSchRescRequiredI(void) {
if (isempty(&rlist))
return FALSE;
if (preempt) {
if (lastprio(&rlist) <= currp->p_prio)
return FALSE;
}
else { /* Time quantum elapsed. */
if (lastprio(&rlist) < currp->p_prio)
return FALSE;
}
return TRUE;
}
/**
* Preemption routine, this function must be called into an interrupt
* handler invoked by a system timer.
* The frequency of the timer determines the system tick granularity and,
* together with the \p CH_TIME_QUANTUM macro, the round robin interval.
*/
void chSchTimerHandlerI(void) {
if (preempt)
preempt--;
#ifdef CH_USE_SYSTEMTIME
stime++;
#endif
#ifdef CH_USE_VIRTUAL_TIMERS
if (&dlist != (DeltaList *)dlist.dl_next) {
VirtualTimer *vtp;
--dlist.dl_next->vt_dtime;
while (!(vtp = dlist.dl_next)->vt_dtime) {
vtp->vt_prev->vt_next = vtp->vt_next;
vtp->vt_next->vt_prev = vtp->vt_prev;
vtp->vt_func(vtp->vt_par);
vtp->vt_func = 0; // Required, flags the timer as triggered.
}
}
#endif
}
/** @} */
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