314 lines
10 KiB
C
314 lines
10 KiB
C
/*
|
|
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 chmtx.c
|
|
* @brief Mutexes code.
|
|
*
|
|
* @addtogroup mutexes
|
|
* @details Mutexes related APIs and services.
|
|
*
|
|
* <h2>Operation mode</h2>
|
|
* A mutex is a threads synchronization object that can be in two
|
|
* distinct states:
|
|
* - Not owned.
|
|
* - Owned by a thread.
|
|
* .
|
|
* Operations defined for mutexes:
|
|
* - <b>Lock</b>: The mutex is checked, if the mutex is not owned by
|
|
* some other thread then it is associated to the locking thread
|
|
* else the thread is queued on the mutex in a list ordered by
|
|
* priority.
|
|
* - <b>Unlock</b>: The mutex is released by the owner and the highest
|
|
* priority thread waiting in the queue, if any, is resumed and made
|
|
* owner of the mutex.
|
|
* .
|
|
* In order to use the Mutexes APIs the @p CH_USE_MUTEXES option must
|
|
* be enabled in @p chconf.h.
|
|
* <h2>Constraints</h2>
|
|
* In ChibiOS/RT the Unlock operations are always performed in
|
|
* lock-reverse order. The unlock API does not even have a parameter,
|
|
* the mutex to unlock is selected from an internal, per-thread, stack
|
|
* of owned mutexes. This both improves the performance and is
|
|
* required for an efficient implementation of the priority
|
|
* inheritance mechanism.
|
|
*
|
|
* <h2>The priority inversion problem</h2>
|
|
* The mutexes in ChibiOS/RT implements the <b>full</b> priority
|
|
* inheritance mechanism in order handle the priority inversion
|
|
* problem.<br>
|
|
* When a thread is queued on a mutex, any thread, directly or
|
|
* indirectly, holding the mutex gains the same priority of the
|
|
* waiting thread (if their priority was not already equal or higher).
|
|
* The mechanism works with any number of nested mutexes and any
|
|
* number of involved threads. The algorithm complexity (worst case)
|
|
* is N with N equal to the number of nested 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 */
|
|
|
|
/** @} */
|