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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/>.
*/
/**
* @file chmtx.c
* @brief Mutexes code.
*
* @addtogroup mutexes
* @{
*/
#include "ch.h"
#if CH_USE_MUTEXES
/**
* @brief Initializes s @p Mutex structure.
*
* @param[out] mp pointer to a @p Mutex structure
*/
void chMtxInit(Mutex *mp) {
chDbgCheck(mp != NULL, "chMtxInit");
queue_init(&mp->m_queue);
mp->m_owner = NULL;
}
/**
* @brief Locks the specified mutex.
*
* @param[in] mp pointer to the @p Mutex structure
*/
void chMtxLock(Mutex *mp) {
chSysLock();
chMtxLockS(mp);
chSysUnlock();
}
/**
* @brief Locks the specified mutex.
*
* @param[in] mp pointer to the @p Mutex structure
*/
void chMtxLockS(Mutex *mp) {
Thread *ctp = currp;
chDbgCheck(mp != NULL, "chMtxLockS");
/* Ia the mutex already locked? */
if (mp->m_owner != NULL) {
/* Priority inheritance protocol; explores the thread-mutex dependencies
boosting the priority of all the affected threads to equal the priority
of the running thread requesting the mutex.*/
Thread *tp = mp->m_owner;
/* Does the running thread have higher priority than the mutex
ownning thread? */
while (tp->p_prio < ctp->p_prio) {
/* Make priority of thread tp match the running thread's priority.*/
tp->p_prio = ctp->p_prio;
/* The following states need priority queues reordering.*/
switch (tp->p_state) {
case THD_STATE_WTMTX:
/* Re-enqueues the mutex owner with its new priority.*/
prio_insert(dequeue(tp), (ThreadsQueue *)tp->p_u.wtobjp);
tp = ((Mutex *)tp->p_u.wtobjp)->m_owner;
continue;
#if CH_USE_CONDVARS | CH_USE_SEMAPHORES_PRIORITY | CH_USE_MESSAGES_PRIORITY
#if CH_USE_CONDVARS
case THD_STATE_WTCOND:
#endif
#if CH_USE_SEMAPHORES_PRIORITY
case THD_STATE_WTSEM:
#endif
#if CH_USE_MESSAGES_PRIORITY
case THD_STATE_SNDMSG:
#endif
/* Re-enqueues tp with its new priority on the queue.*/
prio_insert(dequeue(tp), (ThreadsQueue *)tp->p_u.wtobjp);
break;
#endif
case THD_STATE_READY:
/* Re-enqueues tp with its new priority on the ready list.*/
chSchReadyI(dequeue(tp));
}
break;
}
/* Sleep on the mutex.*/
prio_insert(ctp, &mp->m_queue);
ctp->p_u.wtobjp = mp;
chSchGoSleepS(THD_STATE_WTMTX);
chDbgAssert(mp->m_owner == NULL, "chMtxLockS(), #1", "still owned");
}
/* The mutex is now inserted in the owned mutexes list.*/
mp->m_owner = ctp;
mp->m_next = ctp->p_mtxlist;
ctp->p_mtxlist = mp;
}
/**
* @brief Tries to lock a mutex.
* @details 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[in] mp pointer to the @p Mutex structure
* @retval TRUE if the mutex was successfully acquired
* @retval FALSE if the lock attempt failed.
*/
bool_t chMtxTryLock(Mutex *mp) {
bool_t b;
chSysLock();
b = chMtxTryLockS(mp);
chSysUnlock();
return b;
}
/**
* @brief Tries to lock a mutex.
* @details 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[in] mp pointer to the @p Mutex structure
* @retval TRUE if the mutex was successfully acquired
* @retval FALSE if the lock attempt failed.
*/
bool_t chMtxTryLockS(Mutex *mp) {
chDbgCheck(mp != NULL, "chMtxTryLockS");
if (mp->m_owner != NULL)
return FALSE;
mp->m_owner = currp;
mp->m_next = currp->p_mtxlist;
currp->p_mtxlist = mp;
return TRUE;
}
/**
* @brief Unlocks the next owned mutex in reverse lock order.
*
* @return The pointer to the unlocked mutex.
*/
Mutex *chMtxUnlock(void) {
Thread *ctp = currp;
Mutex *ump, *mp;
chSysLock();
chDbgAssert(ctp->p_mtxlist != NULL,
"chMtxUnlock(), #1",
"owned mutexes list empty");
chDbgAssert(ctp->p_mtxlist->m_owner == ctp,
"chMtxUnlock(), #2",
"ownership failure");
/* Removes the top Mutex from the Threads's owned mutexes list and matk it
as not owned.*/
ump = ctp->p_mtxlist;
ctp->p_mtxlist = ump->m_next;
ump->m_owner = NULL;
/* If a thread is waiting on the mutex then the fun part begins.*/
if (chMtxQueueNotEmptyS(ump)) {
/* Recalculates the optimal thread priority by scanning the owned
mutexes list.*/
tprio_t newprio = ctp->p_realprio;
mp = ctp->p_mtxlist;
while (mp != NULL) {
/* If the highest priority thread waiting in the mutexes list has a
greater priority than the current thread base priority then the final
priority will have at least that priority.*/
if (chMtxQueueNotEmptyS(mp) && (mp->m_queue.p_next->p_prio > newprio))
newprio = mp->m_queue.p_next->p_prio;
mp = mp->m_next;
}
/* Assigns to the current thread the highest priority among all the
waiting threads.*/
ctp->p_prio = newprio;
/* Awakens the highest priority thread waiting for the unlocked mutex.*/
chSchWakeupS(fifo_remove(&ump->m_queue), RDY_OK);
}
chSysUnlock();
return ump;
}
/**
* @brief Unlocks the next owned mutex in reverse lock order.
* @note This function does not reschedule internally.
*
* @return The pointer to the unlocked mutex.
*/
Mutex *chMtxUnlockS(void) {
Thread *ctp = currp;
Mutex *ump, *mp;
chDbgAssert(ctp->p_mtxlist != NULL,
"chMtxUnlockS(), #1",
"owned mutexes list empty");
chDbgAssert(ctp->p_mtxlist->m_owner == ctp,
"chMtxUnlockS(), #2",
"ownership failure");
/* Removes the top Mutex from the owned mutexes list and marks it as not
owned.*/
ump = ctp->p_mtxlist;
ctp->p_mtxlist = ump->m_next;
ump->m_owner = NULL;
/* If a thread is waiting on the mutex then the fun part begins.*/
if (chMtxQueueNotEmptyS(ump)) {
/* Recalculates the optimal thread priority by scanning the owned
mutexes list.*/
tprio_t newprio = ctp->p_realprio;
mp = ctp->p_mtxlist;
while (mp != NULL) {
/* If the highest priority thread waiting in the mutexes list has a
greater priority than the current thread base priority then the final
priority will have at least that priority.*/
if (chMtxQueueNotEmptyS(mp) && (mp->m_queue.p_next->p_prio > newprio))
newprio = mp->m_queue.p_next->p_prio;
mp = mp->m_next;
}
ctp->p_prio = newprio;
chSchReadyI(fifo_remove(&ump->m_queue));
}
return ump;
}
/**
* @brief Unlocks all the mutexes owned by the invoking thread.
* @details This function 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) {
Thread *ctp = currp;
chSysLock();
if (ctp->p_mtxlist != NULL) {
do {
Mutex *mp = ctp->p_mtxlist;
ctp->p_mtxlist = mp->m_next;
mp->m_owner = NULL;
if (chMtxQueueNotEmptyS(mp))
chSchReadyI(fifo_remove(&mp->m_queue));
} while (ctp->p_mtxlist != NULL);
ctp->p_prio = ctp->p_realprio;
chSchRescheduleS();
}
chSysUnlock();
}
#endif /* CH_USE_MUTEXES */
/** @} */
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