diff options
Diffstat (limited to 'lib/libpthread/thread/thr_mutex.c')
| -rw-r--r-- | lib/libpthread/thread/thr_mutex.c | 1258 |
1 files changed, 1071 insertions, 187 deletions
diff --git a/lib/libpthread/thread/thr_mutex.c b/lib/libpthread/thread/thr_mutex.c index d3801f1..0103a6c 100644 --- a/lib/libpthread/thread/thr_mutex.c +++ b/lib/libpthread/thread/thr_mutex.c @@ -20,7 +20,7 @@ * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE - * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) @@ -33,78 +33,116 @@ #include <stdlib.h> #include <errno.h> #include <string.h> +#include <sys/param.h> +#include <sys/queue.h> #ifdef _THREAD_SAFE #include <pthread.h> #include "pthread_private.h" + +/* + * Prototypes + */ +static inline int mutex_self_trylock(pthread_mutex_t); +static inline int mutex_self_lock(pthread_mutex_t); +static inline int mutex_unlock_common(pthread_mutex_t *, int); +static void mutex_priority_adjust(pthread_mutex_t); +static void mutex_rescan_owned (pthread_t, pthread_mutex_t); +static inline pthread_t mutex_queue_deq(pthread_mutex_t); +static inline void mutex_queue_remove(pthread_mutex_t, pthread_t); +static inline void mutex_queue_enq(pthread_mutex_t, pthread_t); + + static spinlock_t static_init_lock = _SPINLOCK_INITIALIZER; + int pthread_mutex_init(pthread_mutex_t * mutex, const pthread_mutexattr_t * mutex_attr) { - enum pthread_mutextype type; + enum pthread_mutextype type; + int protocol; + int ceiling; pthread_mutex_t pmutex; int ret = 0; - if (mutex == NULL) { + if (mutex == NULL) ret = EINVAL; - } else { - /* Check if default mutex attributes: */ - if (mutex_attr == NULL || *mutex_attr == NULL) - /* Default to a fast mutex: */ - type = PTHREAD_MUTEX_DEFAULT; - else if ((*mutex_attr)->m_type >= MUTEX_TYPE_MAX) - /* Return an invalid argument error: */ - ret = EINVAL; - else - /* Use the requested mutex type: */ - type = (*mutex_attr)->m_type; - - /* Check no errors so far: */ - if (ret == 0) { - if ((pmutex = (pthread_mutex_t) - malloc(sizeof(struct pthread_mutex))) == NULL) - ret = ENOMEM; - else { - /* Reset the mutex flags: */ - pmutex->m_flags = 0; - - /* Process according to mutex type: */ - switch (type) { - /* Fast mutex: */ - case PTHREAD_MUTEX_DEFAULT: - case PTHREAD_MUTEX_NORMAL: - case PTHREAD_MUTEX_ERRORCHECK: - /* Nothing to do here. */ - break; - - /* Counting mutex: */ - case PTHREAD_MUTEX_RECURSIVE: - /* Reset the mutex count: */ - pmutex->m_data.m_count = 0; - break; - - /* Trap invalid mutex types: */ - default: - /* Return an invalid argument error: */ - ret = EINVAL; - break; - } - if (ret == 0) { - /* Initialise the rest of the mutex: */ - _thread_queue_init(&pmutex->m_queue); - pmutex->m_flags |= MUTEX_FLAGS_INITED; - pmutex->m_owner = NULL; - pmutex->m_type = type; - memset(&pmutex->lock, 0, - sizeof(pmutex->lock)); - *mutex = pmutex; - } else { - free(pmutex); - *mutex = NULL; - } + /* Check if default mutex attributes: */ + else if (mutex_attr == NULL || *mutex_attr == NULL) { + /* Default to a (error checking) POSIX mutex: */ + type = PTHREAD_MUTEX_ERRORCHECK; + protocol = PTHREAD_PRIO_NONE; + ceiling = PTHREAD_MAX_PRIORITY; + } + + /* Check mutex type: */ + else if (((*mutex_attr)->m_type < PTHREAD_MUTEX_ERRORCHECK) || + ((*mutex_attr)->m_type >= MUTEX_TYPE_MAX)) + /* Return an invalid argument error: */ + ret = EINVAL; + + /* Check mutex protocol: */ + else if (((*mutex_attr)->m_protocol < PTHREAD_PRIO_NONE) || + ((*mutex_attr)->m_protocol > PTHREAD_MUTEX_RECURSIVE)) + /* Return an invalid argument error: */ + ret = EINVAL; + + else { + /* Use the requested mutex type and protocol: */ + type = (*mutex_attr)->m_type; + protocol = (*mutex_attr)->m_protocol; + ceiling = (*mutex_attr)->m_ceiling; + } + + /* Check no errors so far: */ + if (ret == 0) { + if ((pmutex = (pthread_mutex_t) + malloc(sizeof(struct pthread_mutex))) == NULL) + ret = ENOMEM; + else { + /* Reset the mutex flags: */ + pmutex->m_flags = 0; + + /* Process according to mutex type: */ + switch (type) { + /* case PTHREAD_MUTEX_DEFAULT: */ + case PTHREAD_MUTEX_ERRORCHECK: + case PTHREAD_MUTEX_NORMAL: + /* Nothing to do here. */ + break; + + /* Single UNIX Spec 2 recursive mutex: */ + case PTHREAD_MUTEX_RECURSIVE: + /* Reset the mutex count: */ + pmutex->m_data.m_count = 0; + break; + + /* Trap invalid mutex types: */ + default: + /* Return an invalid argument error: */ + ret = EINVAL; + break; + } + if (ret == 0) { + /* Initialise the rest of the mutex: */ + TAILQ_INIT(&pmutex->m_queue); + pmutex->m_flags |= MUTEX_FLAGS_INITED; + pmutex->m_owner = NULL; + pmutex->m_type = type; + pmutex->m_protocol = protocol; + pmutex->m_refcount = 0; + if (protocol == PTHREAD_PRIO_PROTECT) + pmutex->m_prio = ceiling; + else + pmutex->m_prio = 0; + pmutex->m_saved_prio = 0; + memset(&pmutex->lock, 0, sizeof(pmutex->lock)); + *mutex = pmutex; + } else { + free(pmutex); + *mutex = NULL; } } } @@ -124,16 +162,29 @@ pthread_mutex_destroy(pthread_mutex_t * mutex) _SPINLOCK(&(*mutex)->lock); /* - * Free the memory allocated for the mutex - * structure: + * Check to see if this mutex is in use: */ - free(*mutex); + if (((*mutex)->m_owner != NULL) || + (TAILQ_FIRST(&(*mutex)->m_queue) != NULL) || + ((*mutex)->m_refcount != 0)) { + ret = EBUSY; - /* - * Leave the caller's pointer NULL now that - * the mutex has been destroyed: - */ - *mutex = NULL; + /* Unlock the mutex structure: */ + _SPINUNLOCK(&(*mutex)->lock); + } + else { + /* + * Free the memory allocated for the mutex + * structure: + */ + free(*mutex); + + /* + * Leave the caller's pointer NULL now that + * the mutex has been destroyed: + */ + *mutex = NULL; + } } /* Return the completion status: */ @@ -170,44 +221,100 @@ pthread_mutex_trylock(pthread_mutex_t * mutex) * initialization: */ else if (*mutex != NULL || (ret = init_static(mutex)) == 0) { + /* + * Guard against being preempted by a scheduling signal. + * To support priority inheritence mutexes, we need to + * maintain lists of mutex ownerships for each thread as + * well as lists of waiting threads for each mutex. In + * order to propagate priorities we need to atomically + * walk these lists and cannot rely on a single mutex + * lock to provide protection against modification. + */ + _thread_kern_sched_defer(); + /* Lock the mutex structure: */ _SPINLOCK(&(*mutex)->lock); /* Process according to mutex type: */ - switch ((*mutex)->m_type) { - /* Fast mutex: */ - case PTHREAD_MUTEX_NORMAL: - case PTHREAD_MUTEX_DEFAULT: - case PTHREAD_MUTEX_ERRORCHECK: + switch ((*mutex)->m_protocol) { + /* Default POSIX mutex: */ + case PTHREAD_PRIO_NONE: /* Check if this mutex is not locked: */ if ((*mutex)->m_owner == NULL) { /* Lock the mutex for the running thread: */ (*mutex)->m_owner = _thread_run; - } else { + + /* Add to the list of owned mutexes: */ + TAILQ_INSERT_TAIL(&_thread_run->mutexq, + (*mutex), m_qe); + } else if ((*mutex)->m_owner == _thread_run) + ret = mutex_self_trylock(*mutex); + else /* Return a busy error: */ ret = EBUSY; - } break; - /* Counting mutex: */ - case PTHREAD_MUTEX_RECURSIVE: - /* Check if this mutex is locked: */ - if ((*mutex)->m_owner != NULL) { + /* POSIX priority inheritence mutex: */ + case PTHREAD_PRIO_INHERIT: + /* Check if this mutex is not locked: */ + if ((*mutex)->m_owner == NULL) { + /* Lock the mutex for the running thread: */ + (*mutex)->m_owner = _thread_run; + + /* Track number of priority mutexes owned: */ + _thread_run->priority_mutex_count++; + /* - * Check if the mutex is locked by the running - * thread: + * The mutex takes on the attributes of the + * running thread when there are no waiters. */ - if ((*mutex)->m_owner == _thread_run) { - /* Increment the lock count: */ - (*mutex)->m_data.m_count++; - } else { - /* Return a busy error: */ - ret = EBUSY; - } - } else { + (*mutex)->m_prio = _thread_run->active_priority; + (*mutex)->m_saved_prio = + _thread_run->inherited_priority; + + /* Add to the list of owned mutexes: */ + TAILQ_INSERT_TAIL(&_thread_run->mutexq, + (*mutex), m_qe); + } else if ((*mutex)->m_owner == _thread_run) + ret = mutex_self_trylock(*mutex); + else + /* Return a busy error: */ + ret = EBUSY; + break; + + /* POSIX priority protection mutex: */ + case PTHREAD_PRIO_PROTECT: + /* Check for a priority ceiling violation: */ + if (_thread_run->active_priority > (*mutex)->m_prio) + ret = EINVAL; + + /* Check if this mutex is not locked: */ + else if ((*mutex)->m_owner == NULL) { /* Lock the mutex for the running thread: */ (*mutex)->m_owner = _thread_run; - } + + /* Track number of priority mutexes owned: */ + _thread_run->priority_mutex_count++; + + /* + * The running thread inherits the ceiling + * priority of the mutex and executes at that + * priority. + */ + _thread_run->active_priority = (*mutex)->m_prio; + (*mutex)->m_saved_prio = + _thread_run->inherited_priority; + _thread_run->inherited_priority = + (*mutex)->m_prio; + + /* Add to the list of owned mutexes: */ + TAILQ_INSERT_TAIL(&_thread_run->mutexq, + (*mutex), m_qe); + } else if ((*mutex)->m_owner == _thread_run) + ret = mutex_self_trylock(*mutex); + else + /* Return a busy error: */ + ret = EBUSY; break; /* Trap invalid mutex types: */ @@ -219,6 +326,12 @@ pthread_mutex_trylock(pthread_mutex_t * mutex) /* Unlock the mutex structure: */ _SPINUNLOCK(&(*mutex)->lock); + + /* + * Renable preemption and yield if a scheduling signal + * arrived while in the critical region: + */ + _thread_kern_sched_undefer(); } /* Return the completion status: */ @@ -238,91 +351,200 @@ pthread_mutex_lock(pthread_mutex_t * mutex) * initialization: */ else if (*mutex != NULL || (ret = init_static(mutex)) == 0) { + /* + * Guard against being preempted by a scheduling signal. + * To support priority inheritence mutexes, we need to + * maintain lists of mutex ownerships for each thread as + * well as lists of waiting threads for each mutex. In + * order to propagate priorities we need to atomically + * walk these lists and cannot rely on a single mutex + * lock to provide protection against modification. + */ + _thread_kern_sched_defer(); + /* Lock the mutex structure: */ _SPINLOCK(&(*mutex)->lock); /* Process according to mutex type: */ - switch ((*mutex)->m_type) { - /* What SS2 define as a 'normal' mutex. This has to deadlock - on attempts to get a lock you already own. */ - case PTHREAD_MUTEX_NORMAL: - if ((*mutex)->m_owner == _thread_run) { - /* Intetionally deadlock */ - for (;;) - _thread_kern_sched_state(PS_MUTEX_WAIT, __FILE__, __LINE__); - } - goto COMMON_LOCK; - - /* Return error (not OK) on attempting to re-lock */ - case PTHREAD_MUTEX_ERRORCHECK: - if ((*mutex)->m_owner == _thread_run) { - ret = EDEADLK; - break; - } - - /* Fast mutexes do not check for any error conditions: */ - case PTHREAD_MUTEX_DEFAULT: - COMMON_LOCK: - /* - * Enter a loop to wait for the mutex to be locked by the - * current thread: - */ - while ((*mutex)->m_owner != _thread_run) { - /* Check if the mutex is not locked: */ - if ((*mutex)->m_owner == NULL) { - /* Lock the mutex for this thread: */ - (*mutex)->m_owner = _thread_run; - } else { - /* - * Join the queue of threads waiting to lock - * the mutex: - */ - _thread_queue_enq(&(*mutex)->m_queue, _thread_run); + switch ((*mutex)->m_protocol) { + /* Default POSIX mutex: */ + case PTHREAD_PRIO_NONE: + if ((*mutex)->m_owner == NULL) { + /* Lock the mutex for this thread: */ + (*mutex)->m_owner = _thread_run; - /* Wait for the mutex: */ - _thread_kern_sched_state_unlock( - PS_MUTEX_WAIT, &(*mutex)->lock, - __FILE__, __LINE__); + /* Add to the list of owned mutexes: */ + TAILQ_INSERT_TAIL(&_thread_run->mutexq, + (*mutex), m_qe); - /* Lock the mutex again: */ - _SPINLOCK(&(*mutex)->lock); - } + } else if ((*mutex)->m_owner == _thread_run) + ret = mutex_self_lock(*mutex); + else { + /* + * Join the queue of threads waiting to lock + * the mutex: + */ + mutex_queue_enq(*mutex, _thread_run); + + /* + * Keep a pointer to the mutex this thread + * is waiting on: + */ + _thread_run->data.mutex = *mutex; + + /* + * Unlock the mutex structure and schedule the + * next thread: + */ + _thread_kern_sched_state_unlock(PS_MUTEX_WAIT, + &(*mutex)->lock, __FILE__, __LINE__); + + /* Lock the mutex structure again: */ + _SPINLOCK(&(*mutex)->lock); + + /* + * This thread is no longer waiting for + * the mutex: + */ + _thread_run->data.mutex = NULL; } break; - /* Counting mutex: */ - case PTHREAD_MUTEX_RECURSIVE: - /* - * Enter a loop to wait for the mutex to be locked by the - * current thread: - */ - while ((*mutex)->m_owner != _thread_run) { - /* Check if the mutex is not locked: */ - if ((*mutex)->m_owner == NULL) { - /* Lock the mutex for this thread: */ - (*mutex)->m_owner = _thread_run; - - /* Reset the lock count for this mutex: */ - (*mutex)->m_data.m_count = 0; - } else { - /* - * Join the queue of threads waiting to lock - * the mutex: - */ - _thread_queue_enq(&(*mutex)->m_queue, _thread_run); + /* POSIX priority inheritence mutex: */ + case PTHREAD_PRIO_INHERIT: + /* Check if this mutex is not locked: */ + if ((*mutex)->m_owner == NULL) { + /* Lock the mutex for this thread: */ + (*mutex)->m_owner = _thread_run; - /* Wait for the mutex: */ - _thread_kern_sched_state_unlock( - PS_MUTEX_WAIT, &(*mutex)->lock, - __FILE__, __LINE__); + /* Track number of priority mutexes owned: */ + _thread_run->priority_mutex_count++; - /* Lock the mutex again: */ - _SPINLOCK(&(*mutex)->lock); - } + /* + * The mutex takes on attributes of the + * running thread when there are no waiters. + */ + (*mutex)->m_prio = _thread_run->active_priority; + (*mutex)->m_saved_prio = + _thread_run->inherited_priority; + _thread_run->inherited_priority = + (*mutex)->m_prio; + + /* Add to the list of owned mutexes: */ + TAILQ_INSERT_TAIL(&_thread_run->mutexq, + (*mutex), m_qe); + + } else if ((*mutex)->m_owner == _thread_run) + ret = mutex_self_lock(*mutex); + else { + /* + * Join the queue of threads waiting to lock + * the mutex: + */ + mutex_queue_enq(*mutex, _thread_run); + + /* + * Keep a pointer to the mutex this thread + * is waiting on: + */ + _thread_run->data.mutex = *mutex; + + if (_thread_run->active_priority > + (*mutex)->m_prio) + /* Adjust priorities: */ + mutex_priority_adjust(*mutex); + + /* + * Unlock the mutex structure and schedule the + * next thread: + */ + _thread_kern_sched_state_unlock(PS_MUTEX_WAIT, + &(*mutex)->lock, __FILE__, __LINE__); + + /* Lock the mutex structure again: */ + _SPINLOCK(&(*mutex)->lock); + + /* + * This thread is no longer waiting for + * the mutex: + */ + _thread_run->data.mutex = NULL; } + break; + + /* POSIX priority protection mutex: */ + case PTHREAD_PRIO_PROTECT: + /* Check for a priority ceiling violation: */ + if (_thread_run->active_priority > (*mutex)->m_prio) + ret = EINVAL; + + /* Check if this mutex is not locked: */ + else if ((*mutex)->m_owner == NULL) { + /* + * Lock the mutex for the running + * thread: + */ + (*mutex)->m_owner = _thread_run; + + /* Track number of priority mutexes owned: */ + _thread_run->priority_mutex_count++; - /* Increment the lock count for this mutex: */ - (*mutex)->m_data.m_count++; + /* + * The running thread inherits the ceiling + * priority of the mutex and executes at that + * priority: + */ + _thread_run->active_priority = (*mutex)->m_prio; + (*mutex)->m_saved_prio = + _thread_run->inherited_priority; + _thread_run->inherited_priority = + (*mutex)->m_prio; + + /* Add to the list of owned mutexes: */ + TAILQ_INSERT_TAIL(&_thread_run->mutexq, + (*mutex), m_qe); + } else if ((*mutex)->m_owner == _thread_run) + ret = mutex_self_lock(*mutex); + else { + /* + * Join the queue of threads waiting to lock + * the mutex: + */ + mutex_queue_enq(*mutex, _thread_run); + + /* + * Keep a pointer to the mutex this thread + * is waiting on: + */ + _thread_run->data.mutex = *mutex; + + /* Clear any previous error: */ + _thread_run->error = 0; + + /* + * Unlock the mutex structure and schedule the + * next thread: + */ + _thread_kern_sched_state_unlock(PS_MUTEX_WAIT, + &(*mutex)->lock, __FILE__, __LINE__); + + /* Lock the mutex structure again: */ + _SPINLOCK(&(*mutex)->lock); + + /* + * The threads priority may have changed while + * waiting for the mutex causing a ceiling + * violation. + */ + ret = _thread_run->error; + _thread_run->error = 0; + + /* + * This thread is no longer waiting for + * the mutex: + */ + _thread_run->data.mutex = NULL; + } break; /* Trap invalid mutex types: */ @@ -334,6 +556,12 @@ pthread_mutex_lock(pthread_mutex_t * mutex) /* Unlock the mutex structure: */ _SPINUNLOCK(&(*mutex)->lock); + + /* + * Renable preemption and yield if a scheduling signal + * arrived while in the critical region: + */ + _thread_kern_sched_undefer(); } /* Return the completion status: */ @@ -343,56 +571,375 @@ pthread_mutex_lock(pthread_mutex_t * mutex) int pthread_mutex_unlock(pthread_mutex_t * mutex) { - int ret = 0; + return (mutex_unlock_common(mutex, /* add reference */ 0)); +} + +int +_mutex_cv_unlock(pthread_mutex_t * mutex) +{ + return (mutex_unlock_common(mutex, /* add reference */ 1)); +} + +int +_mutex_cv_lock(pthread_mutex_t * mutex) +{ + int ret; + if ((ret = pthread_mutex_lock(mutex)) == 0) + (*mutex)->m_refcount--; + return (ret); +} + +static inline int +mutex_self_trylock(pthread_mutex_t mutex) +{ + int ret = 0; + + switch (mutex->m_type) { + + /* case PTHREAD_MUTEX_DEFAULT: */ + case PTHREAD_MUTEX_ERRORCHECK: + case PTHREAD_MUTEX_NORMAL: + /* + * POSIX specifies that mutexes should return EDEADLK if a + * recursive lock is detected. + */ + ret = EBUSY; + break; + + case PTHREAD_MUTEX_RECURSIVE: + /* Increment the lock count: */ + mutex->m_data.m_count++; + break; + + default: + /* Trap invalid mutex types; */ + ret = EINVAL; + } + + return(ret); +} + +static inline int +mutex_self_lock(pthread_mutex_t mutex) +{ + int ret = 0; + + switch (mutex->m_type) { + /* case PTHREAD_MUTEX_DEFAULT: */ + case PTHREAD_MUTEX_ERRORCHECK: + /* + * POSIX specifies that mutexes should return EDEADLK if a + * recursive lock is detected. + */ + ret = EDEADLK; + break; + + case PTHREAD_MUTEX_NORMAL: + /* + * What SS2 define as a 'normal' mutex. Intentionally + * deadlock on attempts to get a lock you already own. + */ + _thread_kern_sched_state_unlock(PS_DEADLOCK, + &mutex->lock, __FILE__, __LINE__); + break; + + case PTHREAD_MUTEX_RECURSIVE: + /* Increment the lock count: */ + mutex->m_data.m_count++; + break; + + default: + /* Trap invalid mutex types; */ + ret = EINVAL; + } + + return(ret); +} + +static inline int +mutex_unlock_common(pthread_mutex_t * mutex, int add_reference) +{ + int ret = 0; if (mutex == NULL || *mutex == NULL) { ret = EINVAL; } else { + /* + * Guard against being preempted by a scheduling signal. + * To support priority inheritence mutexes, we need to + * maintain lists of mutex ownerships for each thread as + * well as lists of waiting threads for each mutex. In + * order to propagate priorities we need to atomically + * walk these lists and cannot rely on a single mutex + * lock to provide protection against modification. + */ + _thread_kern_sched_defer(); + /* Lock the mutex structure: */ _SPINLOCK(&(*mutex)->lock); /* Process according to mutex type: */ - switch ((*mutex)->m_type) { - /* Default & normal mutexes do not really need to check for - any error conditions: */ - case PTHREAD_MUTEX_NORMAL: - case PTHREAD_MUTEX_DEFAULT: - case PTHREAD_MUTEX_ERRORCHECK: - /* Check if the running thread is not the owner of the mutex: */ + switch ((*mutex)->m_protocol) { + /* Default POSIX mutex: */ + case PTHREAD_PRIO_NONE: + /* + * Check if the running thread is not the owner of the + * mutex: + */ if ((*mutex)->m_owner != _thread_run) { - /* Return an invalid argument error: */ - ret = (*mutex)->m_owner ? EPERM : EINVAL; + /* + * Return an invalid argument error for no + * owner and a permission error otherwise: + */ + ret = (*mutex)->m_owner == NULL ? EINVAL : EPERM; } + else if (((*mutex)->m_type == PTHREAD_MUTEX_RECURSIVE) && + ((*mutex)->m_data.m_count > 1)) { + /* Decrement the count: */ + (*mutex)->m_data.m_count--; + } else { + /* + * Clear the count in case this is recursive + * mutex. + */ + (*mutex)->m_data.m_count = 0; + + /* Remove the mutex from the threads queue. */ + TAILQ_REMOVE(&(*mutex)->m_owner->mutexq, + (*mutex), m_qe); + + /* + * Get the next thread from the queue of + * threads waiting on the mutex: + */ + if (((*mutex)->m_owner = + mutex_queue_deq(*mutex)) != NULL) { + /* + * Allow the new owner of the mutex to + * run: + */ + PTHREAD_NEW_STATE((*mutex)->m_owner, + PS_RUNNING); + } + } + break; + + /* POSIX priority inheritence mutex: */ + case PTHREAD_PRIO_INHERIT: /* - * Get the next thread from the queue of threads waiting on - * the mutex: + * Check if the running thread is not the owner of the + * mutex: */ - else if (((*mutex)->m_owner = _thread_queue_deq(&(*mutex)->m_queue)) != NULL) { - /* Allow the new owner of the mutex to run: */ - PTHREAD_NEW_STATE((*mutex)->m_owner,PS_RUNNING); + if ((*mutex)->m_owner != _thread_run) { + /* + * Return an invalid argument error for no + * owner and a permission error otherwise: + */ + ret = (*mutex)->m_owner == NULL ? EINVAL : EPERM; + } + else if (((*mutex)->m_type == PTHREAD_MUTEX_RECURSIVE) && + ((*mutex)->m_data.m_count > 1)) { + /* Decrement the count: */ + (*mutex)->m_data.m_count--; + } else { + /* + * Clear the count in case this is recursive + * mutex. + */ + (*mutex)->m_data.m_count = 0; + + /* + * Restore the threads inherited priority and + * recompute the active priority (being careful + * not to override changes in the threads base + * priority subsequent to locking the mutex). + */ + _thread_run->inherited_priority = + (*mutex)->m_saved_prio; + _thread_run->active_priority = + MAX(_thread_run->inherited_priority, + _thread_run->base_priority); + + /* + * This thread now owns one less priority mutex. + */ + _thread_run->priority_mutex_count--; + + /* Remove the mutex from the threads queue. */ + TAILQ_REMOVE(&(*mutex)->m_owner->mutexq, + (*mutex), m_qe); + + /* + * Get the next thread from the queue of threads + * waiting on the mutex: + */ + if (((*mutex)->m_owner = + mutex_queue_deq(*mutex)) == NULL) + /* This mutex has no priority. */ + (*mutex)->m_prio = 0; + else { + /* + * Track number of priority mutexes owned: + */ + (*mutex)->m_owner->priority_mutex_count++; + + /* + * Add the mutex to the threads list + * of owned mutexes: + */ + TAILQ_INSERT_TAIL(&(*mutex)->m_owner->mutexq, + (*mutex), m_qe); + + /* + * The owner is no longer waiting for + * this mutex: + */ + (*mutex)->m_owner->data.mutex = NULL; + + /* + * Set the priority of the mutex. Since + * our waiting threads are in descending + * priority order, the priority of the + * mutex becomes the active priority of + * the thread we just dequeued. + */ + (*mutex)->m_prio = + (*mutex)->m_owner->active_priority; + + /* + * Save the owning threads inherited + * priority: + */ + (*mutex)->m_saved_prio = + (*mutex)->m_owner->inherited_priority; + + /* + * The owning threads inherited priority + * now becomes his active priority (the + * priority of the mutex). + */ + (*mutex)->m_owner->inherited_priority = + (*mutex)->m_prio; + + /* + * Allow the new owner of the mutex to + * run: + */ + PTHREAD_NEW_STATE((*mutex)->m_owner, + PS_RUNNING); + } } break; - /* Counting mutex: */ - case PTHREAD_MUTEX_RECURSIVE: - /* Check if the running thread is not the owner of the mutex: */ + /* POSIX priority ceiling mutex: */ + case PTHREAD_PRIO_PROTECT: + /* + * Check if the running thread is not the owner of the + * mutex: + */ if ((*mutex)->m_owner != _thread_run) { - /* Return an invalid argument error: */ - ret = EINVAL; + /* + * Return an invalid argument error for no + * owner and a permission error otherwise: + */ + ret = (*mutex)->m_owner == NULL ? EINVAL : EPERM; } - /* Check if there are still counts: */ - else if ((*mutex)->m_data.m_count > 1) { + else if (((*mutex)->m_type == PTHREAD_MUTEX_RECURSIVE) && + ((*mutex)->m_data.m_count > 1)) { /* Decrement the count: */ (*mutex)->m_data.m_count--; } else { + /* + * Clear the count in case this is recursive + * mutex. + */ (*mutex)->m_data.m_count = 0; + /* - * Get the next thread from the queue of threads waiting on - * the mutex: + * Restore the threads inherited priority and + * recompute the active priority (being careful + * not to override changes in the threads base + * priority subsequent to locking the mutex). + */ + _thread_run->inherited_priority = + (*mutex)->m_saved_prio; + _thread_run->active_priority = + MAX(_thread_run->inherited_priority, + _thread_run->base_priority); + + /* + * This thread now owns one less priority mutex. */ - if (((*mutex)->m_owner = _thread_queue_deq(&(*mutex)->m_queue)) != NULL) { - /* Allow the new owner of the mutex to run: */ - PTHREAD_NEW_STATE((*mutex)->m_owner,PS_RUNNING); + _thread_run->priority_mutex_count--; + + /* Remove the mutex from the threads queue. */ + TAILQ_REMOVE(&(*mutex)->m_owner->mutexq, + (*mutex), m_qe); + + /* + * Enter a loop to find a waiting thread whose + * active priority will not cause a ceiling + * violation: + */ + while ((((*mutex)->m_owner = + mutex_queue_deq(*mutex)) != NULL) && + ((*mutex)->m_owner->active_priority > + (*mutex)->m_prio)) { + /* + * Either the mutex ceiling priority + * been lowered and/or this threads + * priority has been raised subsequent + * to this thread being queued on the + * waiting list. + */ + (*mutex)->m_owner->error = EINVAL; + PTHREAD_NEW_STATE((*mutex)->m_owner, + PS_RUNNING); + } + + /* Check for a new owner: */ + if ((*mutex)->m_owner != NULL) { + /* + * Track number of priority mutexes owned: + */ + (*mutex)->m_owner->priority_mutex_count++; + + /* + * Add the mutex to the threads list + * of owned mutexes: + */ + TAILQ_INSERT_TAIL(&(*mutex)->m_owner->mutexq, + (*mutex), m_qe); + + /* + * The owner is no longer waiting for + * this mutex: + */ + (*mutex)->m_owner->data.mutex = NULL; + + /* + * Save the owning threads inherited + * priority: + */ + (*mutex)->m_saved_prio = + (*mutex)->m_owner->inherited_priority; + + /* + * The owning thread inherits the + * ceiling priority of the mutex and + * executes at that priority: + */ + (*mutex)->m_owner->inherited_priority = + (*mutex)->m_prio; + (*mutex)->m_owner->active_priority = + (*mutex)->m_prio; + + /* + * Allow the new owner of the mutex to + * run: + */ + PTHREAD_NEW_STATE((*mutex)->m_owner, + PS_RUNNING); } } break; @@ -404,11 +951,348 @@ pthread_mutex_unlock(pthread_mutex_t * mutex) break; } + if ((ret == 0) && (add_reference != 0)) { + /* Increment the reference count: */ + (*mutex)->m_refcount++; + } + /* Unlock the mutex structure: */ _SPINUNLOCK(&(*mutex)->lock); + + /* + * Renable preemption and yield if a scheduling signal + * arrived while in the critical region: + */ + _thread_kern_sched_undefer(); } /* Return the completion status: */ return (ret); } + + +/* + * This function is called when a change in base priority occurs + * for a thread that is thread holding, or waiting for, a priority + * protection or inheritence mutex. A change in a threads base + * priority can effect changes to active priorities of other threads + * and to the ordering of mutex locking by waiting threads. + * + * This must be called while thread scheduling is deferred. + */ +void +_mutex_notify_priochange(pthread_t pthread) +{ + /* Adjust the priorites of any owned priority mutexes: */ + if (pthread->priority_mutex_count > 0) { + /* + * Rescan the mutexes owned by this thread and correct + * their priorities to account for this threads change + * in priority. This has the side effect of changing + * the threads active priority. + */ + mutex_rescan_owned(pthread, /* rescan all owned */ NULL); + } + + /* + * If this thread is waiting on a priority inheritence mutex, + * check for priority adjustments. A change in priority can + * also effect a ceiling violation(*) for a thread waiting on + * a priority protection mutex; we don't perform the check here + * as it is done in pthread_mutex_unlock. + * + * (*) It should be noted that a priority change to a thread + * _after_ taking and owning a priority ceiling mutex + * does not affect ownership of that mutex; the ceiling + * priority is only checked before mutex ownership occurs. + */ + if (pthread->state == PS_MUTEX_WAIT) { + /* Lock the mutex structure: */ + _SPINLOCK(&pthread->data.mutex->lock); + + /* + * Check to make sure this thread is still in the same state + * (the spinlock above can yield the CPU to another thread): + */ + if (pthread->state == PS_MUTEX_WAIT) { + /* + * Remove and reinsert this thread into the list of + * waiting threads to preserve decreasing priority + * order. + */ + mutex_queue_remove(pthread->data.mutex, pthread); + mutex_queue_enq(pthread->data.mutex, pthread); + + if (pthread->data.mutex->m_protocol == + PTHREAD_PRIO_INHERIT) { + /* Adjust priorities: */ + mutex_priority_adjust(pthread->data.mutex); + } + } + + /* Unlock the mutex structure: */ + _SPINUNLOCK(&pthread->data.mutex->lock); + } +} + +/* + * Called when a new thread is added to the mutex waiting queue or + * when a threads priority changes that is already in the mutex + * waiting queue. + */ +static void +mutex_priority_adjust(pthread_mutex_t mutex) +{ + pthread_t pthread_next, pthread = mutex->m_owner; + int temp_prio; + pthread_mutex_t m = mutex; + + /* + * Calculate the mutex priority as the maximum of the highest + * active priority of any waiting threads and the owning threads + * active priority(*). + * + * (*) Because the owning threads current active priority may + * reflect priority inherited from this mutex (and the mutex + * priority may have changed) we must recalculate the active + * priority based on the threads saved inherited priority + * and its base priority. + */ + pthread_next = TAILQ_FIRST(&m->m_queue); /* should never be NULL */ + temp_prio = MAX(pthread_next->active_priority, + MAX(m->m_saved_prio, pthread->base_priority)); + + /* See if this mutex really needs adjusting: */ + if (temp_prio == m->m_prio) + /* No need to propagate the priority: */ + return; + + /* Set new priority of the mutex: */ + m->m_prio = temp_prio; + + while (m != NULL) { + /* + * Save the threads priority before rescanning the + * owned mutexes: + */ + temp_prio = pthread->active_priority; + + /* + * Fix the priorities for all the mutexes this thread has + * locked since taking this mutex. This also has a + * potential side-effect of changing the threads priority. + */ + mutex_rescan_owned(pthread, m); + + /* + * If the thread is currently waiting on a mutex, check + * to see if the threads new priority has affected the + * priority of the mutex. + */ + if ((temp_prio != pthread->active_priority) && + (pthread->state == PS_MUTEX_WAIT) && + (pthread->data.mutex->m_protocol == PTHREAD_PRIO_INHERIT)) { + /* Grab the mutex this thread is waiting on: */ + m = pthread->data.mutex; + + /* + * The priority for this thread has changed. Remove + * and reinsert this thread into the list of waiting + * threads to preserve decreasing priority order. + */ + mutex_queue_remove(m, pthread); + mutex_queue_enq(m, pthread); + + /* Grab the waiting thread with highest priority: */ + pthread_next = TAILQ_FIRST(&m->m_queue); + + /* + * Calculate the mutex priority as the maximum of the + * highest active priority of any waiting threads and + * the owning threads active priority. + */ + temp_prio = MAX(pthread_next->active_priority, + MAX(m->m_saved_prio, m->m_owner->base_priority)); + + if (temp_prio != m->m_prio) { + /* + * The priority needs to be propagated to the + * mutex this thread is waiting on and up to + * the owner of that mutex. + */ + m->m_prio = temp_prio; + pthread = m->m_owner; + } + else + /* We're done: */ + m = NULL; + + } + else + /* We're done: */ + m = NULL; + } +} + +static void +mutex_rescan_owned (pthread_t pthread, pthread_mutex_t mutex) +{ + int active_prio, inherited_prio; + pthread_mutex_t m; + pthread_t pthread_next; + + /* + * Start walking the mutexes the thread has taken since + * taking this mutex. + */ + if (mutex == NULL) { + /* + * A null mutex means start at the beginning of the owned + * mutex list. + */ + m = TAILQ_FIRST(&pthread->mutexq); + + /* There is no inherited priority yet. */ + inherited_prio = 0; + } + else { + /* + * The caller wants to start after a specific mutex. It + * is assumed that this mutex is a priority inheritence + * mutex and that its priority has been correctly + * calculated. + */ + m = TAILQ_NEXT(mutex, m_qe); + + /* Start inheriting priority from the specified mutex. */ + inherited_prio = mutex->m_prio; + } + active_prio = MAX(inherited_prio, pthread->base_priority); + + while (m != NULL) { + /* + * We only want to deal with priority inheritence + * mutexes. This might be optimized by only placing + * priority inheritence mutexes into the owned mutex + * list, but it may prove to be useful having all + * owned mutexes in this list. Consider a thread + * exiting while holding mutexes... + */ + if (m->m_protocol == PTHREAD_PRIO_INHERIT) { + /* + * Fix the owners saved (inherited) priority to + * reflect the priority of the previous mutex. + */ + m->m_saved_prio = inherited_prio; + + if ((pthread_next = TAILQ_FIRST(&m->m_queue)) != NULL) + /* Recalculate the priority of the mutex: */ + m->m_prio = MAX(active_prio, + pthread_next->active_priority); + else + m->m_prio = active_prio; + + /* Recalculate new inherited and active priorities: */ + inherited_prio = m->m_prio; + active_prio = MAX(m->m_prio, pthread->base_priority); + } + + /* Advance to the next mutex owned by this thread: */ + m = TAILQ_NEXT(m, m_qe); + } + + /* + * Fix the threads inherited priority and recalculate its + * active priority. + */ + pthread->inherited_priority = inherited_prio; + active_prio = MAX(inherited_prio, pthread->base_priority); + + if (active_prio != pthread->active_priority) { + /* + * If this thread is in the priority queue, it must be + * removed and reinserted for its new priority. + */ + if ((pthread != _thread_run) && + (pthread->state == PS_RUNNING)) { + /* + * Remove the thread from the priority queue + * before changing its priority: + */ + PTHREAD_PRIOQ_REMOVE(pthread); + + /* + * POSIX states that if the priority is being + * lowered, the thread must be inserted at the + * head of the queue for its priority if it owns + * any priority protection or inheritence mutexes. + */ + if ((active_prio < pthread->active_priority) && + (pthread->priority_mutex_count > 0)) { + /* Set the new active priority. */ + pthread->active_priority = active_prio; + + PTHREAD_PRIOQ_INSERT_HEAD(pthread); + } + else { + /* Set the new active priority. */ + pthread->active_priority = active_prio; + + PTHREAD_PRIOQ_INSERT_TAIL(pthread); + } + } + else { + /* Set the new active priority. */ + pthread->active_priority = active_prio; + } + } +} + +/* + * Dequeue a waiting thread from the head of a mutex queue in descending + * priority order. + */ +static inline pthread_t +mutex_queue_deq(pthread_mutex_t mutex) +{ + pthread_t pthread; + + if ((pthread = TAILQ_FIRST(&mutex->m_queue)) != NULL) + TAILQ_REMOVE(&mutex->m_queue, pthread, qe); + + return(pthread); +} + +/* + * Remove a waiting thread from a mutex queue in descending priority order. + */ +static inline void +mutex_queue_remove(pthread_mutex_t mutex, pthread_t pthread) +{ + TAILQ_REMOVE(&mutex->m_queue, pthread, qe); +} + +/* + * Enqueue a waiting thread to a queue in descending priority order. + */ +static inline void +mutex_queue_enq(pthread_mutex_t mutex, pthread_t pthread) +{ + pthread_t tid = TAILQ_LAST(&mutex->m_queue, mutex_head); + + /* + * For the common case of all threads having equal priority, + * we perform a quick check against the priority of the thread + * at the tail of the queue. + */ + if ((tid == NULL) || (pthread->active_priority <= tid->active_priority)) + TAILQ_INSERT_TAIL(&mutex->m_queue, pthread, qe); + else { + tid = TAILQ_FIRST(&mutex->m_queue); + while (pthread->active_priority <= tid->active_priority) + tid = TAILQ_NEXT(tid, qe); + TAILQ_INSERT_BEFORE(tid, pthread, qe); + } +} + #endif |
