/* $OpenBSD: uthread_mutex.c,v 1.22 2009/10/28 13:49:10 kurt Exp $ */ /* * Copyright (c) 1995 John Birrell . * 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: uthread_mutex.c,v 1.16 1999/08/28 00:03:40 peter Exp $ */ #include #include #include #include #include #ifdef _THREAD_SAFE #include #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_REMOVE_IF_OWNED(m) do { \ if ((m)->m_qe.tqe_prev != NULL) \ TAILQ_REMOVE(&(m)->m_owner->mutexq, \ (m), m_qe); \ } 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_REMOVE_IF_OWNED(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_REMOVE_IF_OWNED(*mutex); _MUTEX_INIT_LINK(*mutex); (*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; _SPINLOCK_INIT(&(*mutex)->lock); } return (ret); } int pthread_mutex_init(pthread_mutex_t * mutex, const pthread_mutexattr_t * mutex_attr) { pthread_mutex_t pmutex; enum pthread_mutextype type = 0; int protocol = 0; int ceiling = 0; long flags = 0; 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; flags = 0; } /* Check mutex type: */ else if (((*mutex_attr)->m_type < PTHREAD_MUTEX_ERRORCHECK) || ((*mutex_attr)->m_type >= PTHREAD_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_PRIO_PROTECT)) /* 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; flags = (*mutex_attr)->m_flags; } /* Check no errors so far: */ if (ret == 0) { if ((pmutex = (pthread_mutex_t) malloc(sizeof(struct pthread_mutex))) == NULL) ret = ENOMEM; else { /* Set the mutex flags: */ pmutex->m_flags = flags; /* 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); _SPINLOCK_INIT(&pmutex->lock); *mutex = pmutex; } else { free((void *)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((void *)*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); } static int mutex_trylock_common(pthread_mutex_t *mutex) { struct pthread *curthread = _get_curthread(); int ret = 0; PTHREAD_ASSERT((mutex != NULL) && (*mutex != NULL), "Uninitialized mutex in mutex_trylock_common"); /* * 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 = curthread; /* Add to the list of owned mutexes: */ _MUTEX_ASSERT_NOT_OWNED(*mutex); TAILQ_INSERT_TAIL(&curthread->mutexq, (*mutex), m_qe); } else if ((*mutex)->m_owner == curthread) 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 = curthread; /* Track number of priority mutexes owned: */ curthread->priority_mutex_count++; /* * The mutex takes on the attributes of the * running thread when there are no waiters. */ (*mutex)->m_prio = curthread->active_priority; (*mutex)->m_saved_prio = curthread->inherited_priority; /* Add to the list of owned mutexes: */ _MUTEX_ASSERT_NOT_OWNED(*mutex); TAILQ_INSERT_TAIL(&curthread->mutexq, (*mutex), m_qe); } else if ((*mutex)->m_owner == curthread) 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 (curthread->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 = curthread; /* Track number of priority mutexes owned: */ curthread->priority_mutex_count++; /* * The running thread inherits the ceiling * priority of the mutex and executes at that * priority. */ curthread->active_priority = (*mutex)->m_prio; (*mutex)->m_saved_prio = curthread->inherited_priority; curthread->inherited_priority = (*mutex)->m_prio; /* Add to the list of owned mutexes: */ _MUTEX_ASSERT_NOT_OWNED(*mutex); TAILQ_INSERT_TAIL(&curthread->mutexq, (*mutex), m_qe); } else if ((*mutex)->m_owner == curthread) 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_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) ret = mutex_trylock_common(mutex); return (ret); } static int mutex_lock_common(pthread_mutex_t * mutex) { struct pthread *curthread = _get_curthread(); int ret = 0; PTHREAD_ASSERT((mutex != NULL) && (*mutex != NULL), "Uninitialized mutex in mutex_lock_common"); /* Reset the interrupted flag: */ curthread->interrupted = 0; /* * Enter a loop waiting to become the mutex owner. We need a * loop in case the waiting thread is interrupted by a signal * to execute a signal handler. It is not (currently) possible * to remain in the waiting queue while running a handler. * Instead, the thread is interrupted and backed out of the * waiting queue prior to executing the signal handler. */ do { /* * 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); } /* 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 = curthread; /* Add to the list of owned mutexes: */ _MUTEX_ASSERT_NOT_OWNED(*mutex); TAILQ_INSERT_TAIL(&curthread->mutexq, (*mutex), m_qe); } else if ((*mutex)->m_owner == curthread) ret = mutex_self_lock(*mutex); else { /* * Join the queue of threads waiting to lock * the mutex: */ mutex_queue_enq(*mutex, curthread); /* * Keep a pointer to the mutex this thread * is waiting on: */ curthread->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 = curthread; /* Track number of priority mutexes owned: */ curthread->priority_mutex_count++; /* * The mutex takes on attributes of the * running thread when there are no waiters. */ (*mutex)->m_prio = curthread->active_priority; (*mutex)->m_saved_prio = curthread->inherited_priority; curthread->inherited_priority = (*mutex)->m_prio; /* Add to the list of owned mutexes: */ _MUTEX_ASSERT_NOT_OWNED(*mutex); TAILQ_INSERT_TAIL(&curthread->mutexq, (*mutex), m_qe); } else if ((*mutex)->m_owner == curthread) ret = mutex_self_lock(*mutex); else { /* * Join the queue of threads waiting to lock * the mutex: */ mutex_queue_enq(*mutex, curthread); /* * Keep a pointer to the mutex this thread * is waiting on: */ curthread->data.mutex = *mutex; if (curthread->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 (curthread->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 = curthread; /* Track number of priority mutexes owned: */ curthread->priority_mutex_count++; /* * The running thread inherits the ceiling * priority of the mutex and executes at that * priority: */ curthread->active_priority = (*mutex)->m_prio; (*mutex)->m_saved_prio = curthread->inherited_priority; curthread->inherited_priority = (*mutex)->m_prio; /* Add to the list of owned mutexes: */ _MUTEX_ASSERT_NOT_OWNED(*mutex); TAILQ_INSERT_TAIL(&curthread->mutexq, (*mutex), m_qe); } else if ((*mutex)->m_owner == curthread) ret = mutex_self_lock(*mutex); else { /* * Join the queue of threads waiting to lock * the mutex: */ mutex_queue_enq(*mutex, curthread); /* * Keep a pointer to the mutex this thread * is waiting on: */ curthread->data.mutex = *mutex; /* Clear any previous error: */ curthread->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 = curthread->error; curthread->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 (curthread->interrupted != 0) mutex_queue_remove(*mutex, curthread); /* Unlock the mutex structure: */ _SPINUNLOCK(&(*mutex)->lock); /* * Undefer and handle pending signals, yielding if * necessary: */ _thread_kern_sig_undefer(); } while (((*mutex)->m_owner != curthread) && (ret == 0) && (curthread->interrupted == 0)); if (curthread->interrupted != 0 && curthread->continuation != NULL) curthread->continuation(curthread); /* Return the completion status: */ return (ret); } int pthread_mutex_lock(pthread_mutex_t *mutex) { int ret = 0; if (_thread_initial == NULL) _thread_init(); if (mutex == NULL) ret = EINVAL; /* * If the mutex is statically initialized, perform the dynamic * initialization. Note: _thread_mutex_lock() in libc requires * pthread_mutex_lock() to perform the mutex init when *mutex * is NULL. */ else if ((*mutex != NULL) || ((ret = init_static(mutex)) == 0)) ret = mutex_lock_common(mutex); 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) { struct pthread *curthread = _get_curthread(); 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 != curthread) { /* * 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 > 0)) { /* 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) { /* * Unless the new owner of the mutex is * currently suspended, allow the owner * to run. If the thread is suspended, * make a note that the thread isn't in * a wait queue any more. */ if (((*mutex)->m_owner->state != PS_SUSPENDED)) { PTHREAD_NEW_STATE((*mutex)->m_owner, PS_RUNNING); } else { (*mutex)->m_owner->suspended = SUSP_NOWAIT; } /* * 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 != curthread) { /* * 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 > 0)) { /* 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). */ curthread->inherited_priority = (*mutex)->m_saved_prio; curthread->active_priority = MAX(curthread->inherited_priority, curthread->base_priority); /* * This thread now owns one less priority mutex. */ curthread->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; /* * Unless the new owner of the mutex is * currently suspended, allow the owner * to run. If the thread is suspended, * make a note that the thread isn't in * a wait queue any more. */ if (((*mutex)->m_owner->state != PS_SUSPENDED)) { PTHREAD_NEW_STATE((*mutex)->m_owner, PS_RUNNING); } else { (*mutex)->m_owner->suspended = SUSP_NOWAIT; } } } 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 != curthread) { /* * 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 > 0)) { /* 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). */ curthread->inherited_priority = (*mutex)->m_saved_prio; curthread->active_priority = MAX(curthread->inherited_priority, curthread->base_priority); /* * This thread now owns one less priority mutex. */ curthread->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; /* * Unless the new owner of the mutex is * currently suspended, allow the owner * to run. If the thread is suspended, * make a note that the thread isn't in * a wait queue any more. */ if (((*mutex)->m_owner->state != PS_SUSPENDED)) { PTHREAD_NEW_STATE((*mutex)->m_owner, PS_RUNNING); } else { (*mutex)->m_owner->suspended = SUSP_NOWAIT; } } } 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; } } } /* * 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, sqe); 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, sqe); 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); PTHREAD_ASSERT_NOT_IN_SYNCQ(pthread); /* * 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, sqe); else { tid = TAILQ_FIRST(&mutex->m_queue); while (pthread->active_priority <= tid->active_priority) tid = TAILQ_NEXT(tid, sqe); TAILQ_INSERT_BEFORE(tid, pthread, sqe); } pthread->flags |= PTHREAD_FLAGS_IN_MUTEXQ; } #endif