diff options
Diffstat (limited to 'lib/libpthread/thread/thr_mutex.c')
| -rw-r--r-- | lib/libpthread/thread/thr_mutex.c | 1406 |
1 files changed, 1406 insertions, 0 deletions
diff --git a/lib/libpthread/thread/thr_mutex.c b/lib/libpthread/thread/thr_mutex.c new file mode 100644 index 0000000..c625ef2 --- /dev/null +++ b/lib/libpthread/thread/thr_mutex.c @@ -0,0 +1,1406 @@ +/* + * Copyright (c) 1995 John Birrell <jb@cimlogic.com.au>. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by John Birrell. + * 4. Neither the name of the author nor the names of any co-contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * 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 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) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * + * $FreeBSD$ + */ +#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" + +#if defined(_PTHREADS_INVARIANTS) +#define _MUTEX_INIT_LINK(m) do { \ + (m)->m_qe.tqe_prev = NULL; \ + (m)->m_qe.tqe_next = NULL; \ +} while (0) +#define _MUTEX_ASSERT_IS_OWNED(m) do { \ + if ((m)->m_qe.tqe_prev == NULL) \ + PANIC("mutex is not on list"); \ +} while (0) +#define _MUTEX_ASSERT_NOT_OWNED(m) do { \ + if (((m)->m_qe.tqe_prev != NULL) || \ + ((m)->m_qe.tqe_next != NULL)) \ + PANIC("mutex is on list"); \ +} while (0) +#else +#define _MUTEX_INIT_LINK(m) +#define _MUTEX_ASSERT_IS_OWNED(m) +#define _MUTEX_ASSERT_NOT_OWNED(m) +#endif + +/* + * 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; + +/* Reinitialize a mutex to defaults. */ +int +_mutex_reinit(pthread_mutex_t * mutex) +{ + int ret = 0; + + if (mutex == NULL) + ret = EINVAL; + else if (*mutex == NULL) + ret = pthread_mutex_init(mutex, NULL); + else { + /* + * Initialize the mutex structure: + */ + (*mutex)->m_type = PTHREAD_MUTEX_DEFAULT; + (*mutex)->m_protocol = PTHREAD_PRIO_NONE; + TAILQ_INIT(&(*mutex)->m_queue); + (*mutex)->m_owner = NULL; + (*mutex)->m_data.m_count = 0; + (*mutex)->m_flags &= MUTEX_FLAGS_PRIVATE; + (*mutex)->m_flags |= MUTEX_FLAGS_INITED; + (*mutex)->m_refcount = 0; + (*mutex)->m_prio = 0; + (*mutex)->m_saved_prio = 0; + _MUTEX_INIT_LINK(*mutex); + memset(&(*mutex)->lock, 0, sizeof((*mutex)->lock)); + } + return (ret); +} + +int +pthread_mutex_init(pthread_mutex_t * mutex, + const pthread_mutexattr_t * mutex_attr) +{ + enum pthread_mutextype type; + int protocol; + int ceiling; + pthread_mutex_t pmutex; + int ret = 0; + + if (mutex == NULL) + ret = EINVAL; + + /* 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; + _MUTEX_INIT_LINK(pmutex); + memset(&pmutex->lock, 0, sizeof(pmutex->lock)); + *mutex = pmutex; + } else { + free(pmutex); + *mutex = NULL; + } + } + } + /* Return the completion status: */ + return(ret); +} + +int +pthread_mutex_destroy(pthread_mutex_t * mutex) +{ + int ret = 0; + + if (mutex == NULL || *mutex == NULL) + ret = EINVAL; + else { + /* Lock the mutex structure: */ + _SPINLOCK(&(*mutex)->lock); + + /* + * Check to see if this mutex is in use: + */ + if (((*mutex)->m_owner != NULL) || + (TAILQ_FIRST(&(*mutex)->m_queue) != NULL) || + ((*mutex)->m_refcount != 0)) { + ret = EBUSY; + + /* Unlock the mutex structure: */ + _SPINUNLOCK(&(*mutex)->lock); + } + else { + /* + * Free the memory allocated for the mutex + * structure: + */ + _MUTEX_ASSERT_NOT_OWNED(*mutex); + free(*mutex); + + /* + * Leave the caller's pointer NULL now that + * the mutex has been destroyed: + */ + *mutex = NULL; + } + } + + /* Return the completion status: */ + return (ret); +} + +static int +init_static (pthread_mutex_t *mutex) +{ + int ret; + + _SPINLOCK(&static_init_lock); + + if (*mutex == NULL) + ret = pthread_mutex_init(mutex, NULL); + else + ret = 0; + + _SPINUNLOCK(&static_init_lock); + + return(ret); +} + +int +pthread_mutex_trylock(pthread_mutex_t * mutex) +{ + int ret = 0; + + if (mutex == NULL) + ret = EINVAL; + + /* + * If the mutex is statically initialized, perform the dynamic + * initialization: + */ + else if (*mutex != NULL || (ret = init_static(mutex)) == 0) { + /* + * Defer signals to protect the scheduling queues from + * access by the signal handler: + */ + _thread_kern_sig_defer(); + + /* Lock the mutex structure: */ + _SPINLOCK(&(*mutex)->lock); + + /* + * If the mutex was statically allocated, properly + * initialize the tail queue. + */ + if (((*mutex)->m_flags & MUTEX_FLAGS_INITED) == 0) { + TAILQ_INIT(&(*mutex)->m_queue); + _MUTEX_INIT_LINK(*mutex); + (*mutex)->m_flags |= MUTEX_FLAGS_INITED; + } + + /* Process according to mutex type: */ + 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; + + /* Add to the list of owned mutexes: */ + _MUTEX_ASSERT_NOT_OWNED(*mutex); + 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 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++; + + /* + * The mutex takes on the 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; + + /* Add to the list of owned mutexes: */ + _MUTEX_ASSERT_NOT_OWNED(*mutex); + 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: */ + _MUTEX_ASSERT_NOT_OWNED(*mutex); + 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: */ + default: + /* Return an invalid argument error: */ + ret = EINVAL; + break; + } + + /* Unlock the mutex structure: */ + _SPINUNLOCK(&(*mutex)->lock); + + /* + * Undefer and handle pending signals, yielding if + * necessary: + */ + _thread_kern_sig_undefer(); + } + + /* Return the completion status: */ + return (ret); +} + +int +pthread_mutex_lock(pthread_mutex_t * mutex) +{ + int ret = 0; + + if (mutex == NULL) + ret = EINVAL; + + /* + * If the mutex is statically initialized, perform the dynamic + * initialization: + */ + else if (*mutex != NULL || (ret = init_static(mutex)) == 0) { + /* + * Defer signals to protect the scheduling queues from + * access by the signal handler: + */ + _thread_kern_sig_defer(); + + /* Lock the mutex structure: */ + _SPINLOCK(&(*mutex)->lock); + + /* + * If the mutex was statically allocated, properly + * initialize the tail queue. + */ + if (((*mutex)->m_flags & MUTEX_FLAGS_INITED) == 0) { + TAILQ_INIT(&(*mutex)->m_queue); + (*mutex)->m_flags |= MUTEX_FLAGS_INITED; + _MUTEX_INIT_LINK(*mutex); + } + + /* Reset the interrupted flag: */ + _thread_run->interrupted = 0; + + /* Process according to mutex type: */ + 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; + + /* Add to the list of owned mutexes: */ + _MUTEX_ASSERT_NOT_OWNED(*mutex); + 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; + + /* + * 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); + } + break; + + /* 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; + + /* Track number of priority mutexes owned: */ + _thread_run->priority_mutex_count++; + + /* + * 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: */ + _MUTEX_ASSERT_NOT_OWNED(*mutex); + 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); + } + 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: */ + _MUTEX_ASSERT_NOT_OWNED(*mutex); + 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; + } + break; + + /* Trap invalid mutex types: */ + default: + /* Return an invalid argument error: */ + ret = EINVAL; + break; + } + + /* + * Check to see if this thread was interrupted and + * is still in the mutex queue of waiting threads: + */ + if (_thread_run->interrupted != 0) + mutex_queue_remove(*mutex, _thread_run); + + /* Unlock the mutex structure: */ + _SPINUNLOCK(&(*mutex)->lock); + + /* + * Undefer and handle pending signals, yielding if + * necessary: + */ + _thread_kern_sig_undefer(); + + if ((_thread_run->cancelflags & PTHREAD_CANCEL_NEEDED) != 0) { + _thread_run->cancelflags &= ~PTHREAD_CANCEL_NEEDED; + _thread_exit_cleanup(); + pthread_exit(PTHREAD_CANCELED); + } + } + + /* Return the completion status: */ + return (ret); +} + +int +pthread_mutex_unlock(pthread_mutex_t * mutex) +{ + 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 { + /* + * Defer signals to protect the scheduling queues from + * access by the signal handler: + */ + _thread_kern_sig_defer(); + + /* Lock the mutex structure: */ + _SPINLOCK(&(*mutex)->lock); + + /* Process according to mutex type: */ + 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 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. */ + _MUTEX_ASSERT_IS_OWNED(*mutex); + TAILQ_REMOVE(&(*mutex)->m_owner->mutexq, + (*mutex), m_qe); + _MUTEX_INIT_LINK(*mutex); + + /* + * 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); + + /* + * 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; + } + } + break; + + /* POSIX priority inheritence mutex: */ + case PTHREAD_PRIO_INHERIT: + /* + * Check if the running thread is not the owner of the + * mutex: + */ + 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. */ + _MUTEX_ASSERT_IS_OWNED(*mutex); + TAILQ_REMOVE(&(*mutex)->m_owner->mutexq, + (*mutex), m_qe); + _MUTEX_INIT_LINK(*mutex); + + /* + * 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; + + /* 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 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. */ + _MUTEX_ASSERT_IS_OWNED(*mutex); + TAILQ_REMOVE(&(*mutex)->m_owner->mutexq, + (*mutex), m_qe); + _MUTEX_INIT_LINK(*mutex); + + /* + * 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); + /* + * The thread is no longer waiting for + * this mutex: + */ + (*mutex)->m_owner->data.mutex = NULL; + } + + /* 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; + + /* Trap invalid mutex types: */ + default: + /* Return an invalid argument error: */ + ret = EINVAL; + break; + } + + if ((ret == 0) && (add_reference != 0)) { + /* Increment the reference count: */ + (*mutex)->m_refcount++; + } + + /* Unlock the mutex structure: */ + _SPINUNLOCK(&(*mutex)->lock); + + /* + * Undefer and handle pending signals, yielding if + * necessary: + */ + _thread_kern_sig_undefer(); + } + + /* Return the completion status: */ + return (ret); +} + + +/* + * This function is called when a change in base priority occurs for + * a thread that is 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->flags & PTHREAD_FLAGS_IN_PRIOQ) { + /* + * 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; + } + } +} + +void +_mutex_unlock_private(pthread_t pthread) +{ + struct pthread_mutex *m, *m_next; + + for (m = TAILQ_FIRST(&pthread->mutexq); m != NULL; m = m_next) { + m_next = TAILQ_NEXT(m, m_qe); + if ((m->m_flags & MUTEX_FLAGS_PRIVATE) != 0) + pthread_mutex_unlock(&m); + } +} + +/* + * 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; + + while ((pthread = TAILQ_FIRST(&mutex->m_queue)) != NULL) { + TAILQ_REMOVE(&mutex->m_queue, pthread, qe); + pthread->flags &= ~PTHREAD_FLAGS_IN_MUTEXQ; + + /* + * Only exit the loop if the thread hasn't been + * cancelled. + */ + if (pthread->interrupted == 0) + break; + } + + 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) +{ + if ((pthread->flags & PTHREAD_FLAGS_IN_MUTEXQ) != 0) { + TAILQ_REMOVE(&mutex->m_queue, pthread, qe); + pthread->flags &= ~PTHREAD_FLAGS_IN_MUTEXQ; + } +} + +/* + * 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); + } + pthread->flags |= PTHREAD_FLAGS_IN_MUTEXQ; +} + +#endif |
