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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 Mutexes
* @{
*/
#include <ch.h>
#ifdef CH_USE_MUTEXES
/**
* Initializes s \p Mutex structure.
* @param mp pointer to a \p Mutex structure
*/
void chMtxInit(Mutex *mp) {
fifo_init(&mp->m_queue);
mp->m_owner = NULL;
}
/*
* Inserts a thread into a list ordering it by priority.
* @param tp the pointer to the thread to be inserted in the list
* @param tqp the pointer to the threads list header
*/
#ifdef CH_OPTIMIZE_SPEED
static INLINE void prio_enq(Thread *tp, ThreadsQueue *tqp) {
#else
static void prio_enq(Thread *tp, ThreadsQueue *tqp) {
#endif
Thread *cp = tqp->p_next;
while ((cp != (Thread *)tqp) && (cp->p_prio >= tp->p_prio))
cp = cp->p_next;
/* Insertion on p_prev.*/
tp->p_prev = (tp->p_next = cp)->p_prev;
tp->p_prev->p_next = cp->p_prev = tp;
}
/**
* Locks the specified mutex.
* @param mp pointer to the \p Mutex structure
*/
void chMtxLock(Mutex *mp) {
chSysLock();
chMtxLockS(mp);
chSysUnlock();
}
/**
* Locks the specified mutex.
* @param mp pointer to the \p Mutex structure
* @note This function must be called within a \p chSysLock() / \p chSysUnlock()
* block.
*/
void chMtxLockS(Mutex *mp) {
if (mp->m_owner != NULL) {
/*
* Inheritance, explores the thread-mutex dependances adjusting
* the priority of all the affected threads.
*/
Thread *tp = mp->m_owner;
while (tp->p_prio < currp->p_prio) {
tp->p_prio = currp->p_prio;
switch (tp->p_state) {
case PRWTMTX:
prio_enq(dequeue(tp), &tp->p_mtxp->m_queue);
tp = tp->p_mtxp->m_owner;
continue;
case PRREADY:
chSchReadyI(dequeue(tp), RDY_OK);
}
break;
}
/*
* Goes to sleep on the mutex.
*/
prio_enq(currp, &mp->m_queue);
currp->p_mtxp = mp;
chSchGoSleepS(PRWTMTX);
chDbgAssert(mp->m_owner == NULL, "chmtx.c, chMtxLockS()");
}
/*
* The mutex is now inserted in the owned mutexes list.
*/
mp->m_owner = currp;
mp->m_next = currp->p_mtxlist;
currp->p_mtxlist = mp;
}
/**
* Tries to lock a mutex. This function does not have any overhead related to
* the priority inheritance mechanism because it does not try to enter a sleep
* state on the mutex.
* @param mp pointer to the \p Mutex structure
* @return \p TRUE if the mutex was successfully acquired else \p FALSE
*/
BOOL chMtxTryLock(Mutex *mp) {
chSysLock();
BOOL b = chMtxTryLockS(mp);
chSysUnlock();
return b;
}
/**
* Tries to lock a mutex. This function does not have any overhead related to
* the priority inheritance mechanism because it does not try to enter a sleep
* state on the mutex.
* @param mp pointer to the \p Mutex structure
* @return \p TRUE if the mutex was successfully acquired else \p FALSE
* @note This function must be called within a \p chSysLock() / \p chSysUnlock()
* block.
*/
BOOL chMtxTryLockS(Mutex *mp) {
if (mp->m_owner != NULL)
return FALSE;
mp->m_owner = currp;
mp->m_next = currp->p_mtxlist;
currp->p_mtxlist = mp;
return TRUE;
}
/**
* Unlocks the next owned mutex in reverse lock order.
*/
void chMtxUnlock(void) {
chSysLock();
chMtxUnlockS();
chSysUnlock();
}
/**
* Unlocks the next owned mutex in reverse lock order.
* @note This function must be called within a \p chSysLock() / \p chSysUnlock()
* block.
*/
void chMtxUnlockS(void) {
chDbgAssert((currp->p_mtxlist != NULL) && (currp->p_mtxlist->m_owner == currp),
"chmtx.c, chMtxUnlockS()");
/*
* Removes the top Mutex from the owned mutexes list and marks it as not owned.
*/
Mutex *mp = currp->p_mtxlist;
currp->p_mtxlist = mp->m_next;
mp->m_owner = NULL;
/*
* If a thread is waiting on the mutex then the hard part begins.
*/
if (chMtxQueueNotEmptyS(mp)) {
Thread *tp = fifo_remove(&mp->m_queue);
/*
* Recalculates the optimal thread priority by scanning the owned mutexes list.
*/
t_prio newprio = currp->p_realprio;
mp = currp->p_mtxlist;
while (mp != NULL) {
if (chMtxQueueNotEmptyS(mp) && (mp->m_queue.p_next->p_prio > newprio))
newprio = mp->m_queue.p_next->p_prio;
mp = mp->m_next;
}
if (currp->p_prio == newprio)
chSchWakeupS(tp, RDY_OK);
else {
/* Note, changing priority and use chSchWakeupS() is wrong because the
internal optimization, see the chSchWakeupS() notes.*/
currp->p_prio = newprio;
chSchReadyI(tp, RDY_OK);
chSchRescheduleS();
}
}
}
/**
* Unlocks all the mutexes owned by the invoking thread, this is <b>MUCH MORE</b>
* efficient than releasing the mutexes one by one and not just because the
* call overhead, this function does not have any overhead related to the
* priority inheritance mechanism.
*/
void chMtxUnlockAll(void) {
chSysLock();
chMtxUnlockAllS();
chSysUnlock();
}
/**
* Unlocks all the mutexes owned by the invoking thread, this is <b>MUCH MORE</b>
* efficient than releasing the mutexes one by one and not just because the
* call overhead, this function does not have any overhead related to the
* priority inheritance mechanism.
* @note This function must be called within a \p chSysLock() / \p chSysUnlock()
* block.
*/
void chMtxUnlockAllS(void) {
if (currp->p_mtxlist != NULL) {
do {
Mutex *mp = currp->p_mtxlist;
currp->p_mtxlist = mp->m_next;
mp->m_owner = NULL;
if (chMtxQueueNotEmptyS(mp))
chSchReadyI(fifo_remove(&mp->m_queue), RDY_OK);
} while (currp->p_mtxlist != NULL);
currp->p_prio = currp->p_realprio;
chSchRescheduleS();
}
}
#endif /* CH_USE_MUTEXES */
/** @} */
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