541 lines
14 KiB
C
541 lines
14 KiB
C
/*
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* Copyright (c) 1995 John Birrell <jb@cimlogic.com.au>.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by John Birrell.
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* 4. Neither the name of the author nor the names of any co-contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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*/
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#include <stdlib.h>
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#include <errno.h>
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#include <string.h>
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#ifdef _THREAD_SAFE
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#include <pthread.h>
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#include "pthread_private.h"
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/*
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* Prototypes
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*/
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static inline pthread_t cond_queue_deq(pthread_cond_t);
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static inline void cond_queue_remove(pthread_cond_t, pthread_t);
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static inline void cond_queue_enq(pthread_cond_t, pthread_t);
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int
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pthread_cond_init(pthread_cond_t * cond, const pthread_condattr_t * cond_attr)
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{
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enum pthread_cond_type type;
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pthread_cond_t pcond;
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int rval = 0;
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if (cond == NULL)
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rval = EINVAL;
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else {
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/*
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* Check if a pointer to a condition variable attribute
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* structure was passed by the caller:
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*/
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if (cond_attr != NULL && *cond_attr != NULL) {
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/* Default to a fast condition variable: */
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type = (*cond_attr)->c_type;
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} else {
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/* Default to a fast condition variable: */
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type = COND_TYPE_FAST;
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}
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/* Process according to condition variable type: */
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switch (type) {
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/* Fast condition variable: */
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case COND_TYPE_FAST:
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/* Nothing to do here. */
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break;
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/* Trap invalid condition variable types: */
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default:
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/* Return an invalid argument error: */
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rval = EINVAL;
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break;
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}
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/* Check for no errors: */
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if (rval == 0) {
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if ((pcond = (pthread_cond_t)
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malloc(sizeof(struct pthread_cond))) == NULL) {
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rval = ENOMEM;
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} else {
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/*
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* Initialise the condition variable
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* structure:
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*/
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TAILQ_INIT(&pcond->c_queue);
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pcond->c_flags |= COND_FLAGS_INITED;
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pcond->c_type = type;
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pcond->c_mutex = NULL;
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memset(&pcond->lock,0,sizeof(pcond->lock));
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*cond = pcond;
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}
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}
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}
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/* Return the completion status: */
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return (rval);
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}
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int
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pthread_cond_destroy(pthread_cond_t * cond)
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{
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int rval = 0;
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if (cond == NULL || *cond == NULL)
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rval = EINVAL;
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else {
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/* Lock the condition variable structure: */
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_SPINLOCK(&(*cond)->lock);
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/*
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* Free the memory allocated for the condition
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* variable structure:
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*/
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free(*cond);
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/*
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* NULL the caller's pointer now that the condition
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* variable has been destroyed:
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*/
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*cond = NULL;
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}
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/* Return the completion status: */
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return (rval);
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}
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int
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pthread_cond_wait(pthread_cond_t * cond, pthread_mutex_t * mutex)
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{
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int rval = 0;
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int status;
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if (cond == NULL)
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rval = EINVAL;
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/*
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* If the condition variable is statically initialized,
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* perform the dynamic initialization:
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*/
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else if (*cond != NULL ||
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(rval = pthread_cond_init(cond,NULL)) == 0) {
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/*
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* If the condvar was statically allocated, properly
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* initialize the tail queue.
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*/
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if (((*cond)->c_flags & COND_FLAGS_INITED) == 0) {
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TAILQ_INIT(&(*cond)->c_queue);
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(*cond)->c_flags |= COND_FLAGS_INITED;
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}
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/* Lock the condition variable structure: */
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_SPINLOCK(&(*cond)->lock);
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/* Process according to condition variable type: */
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switch ((*cond)->c_type) {
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/* Fast condition variable: */
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case COND_TYPE_FAST:
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if ((mutex == NULL) || (((*cond)->c_mutex != NULL) &&
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((*cond)->c_mutex != *mutex))) {
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/* Unlock the condition variable structure: */
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_SPINUNLOCK(&(*cond)->lock);
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/* Return invalid argument error: */
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rval = EINVAL;
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} else {
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/* Reset the timeout flag: */
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_thread_run->timeout = 0;
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/*
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* Queue the running thread for the condition
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* variable:
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*/
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cond_queue_enq(*cond, _thread_run);
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/* Remember the mutex that is being used: */
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(*cond)->c_mutex = *mutex;
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/* Wait forever: */
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_thread_run->wakeup_time.tv_sec = -1;
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/* Unlock the mutex: */
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if ((rval = _mutex_cv_unlock(mutex)) != 0) {
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/*
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* Cannot unlock the mutex, so remove
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* the running thread from the condition
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* variable queue:
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*/
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cond_queue_remove(*cond, _thread_run);
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/* Check for no more waiters: */
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if (TAILQ_FIRST(&(*cond)->c_queue) ==
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NULL)
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(*cond)->c_mutex = NULL;
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/* Unlock the condition variable structure: */
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_SPINUNLOCK(&(*cond)->lock);
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}
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else {
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/*
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* Schedule the next thread and unlock
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* the condition variable structure:
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*/
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_thread_kern_sched_state_unlock(PS_COND_WAIT,
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&(*cond)->lock, __FILE__, __LINE__);
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/* Lock the mutex: */
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rval = _mutex_cv_lock(mutex);
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}
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}
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break;
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/* Trap invalid condition variable types: */
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default:
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/* Unlock the condition variable structure: */
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_SPINUNLOCK(&(*cond)->lock);
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/* Return an invalid argument error: */
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rval = EINVAL;
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break;
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}
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}
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/* Return the completion status: */
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return (rval);
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}
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int
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pthread_cond_timedwait(pthread_cond_t * cond, pthread_mutex_t * mutex,
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const struct timespec * abstime)
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{
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int rval = 0;
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int status;
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if (cond == NULL)
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rval = EINVAL;
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/*
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* If the condition variable is statically initialized,
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* perform the dynamic initialization:
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*/
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else if (*cond != NULL ||
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(rval = pthread_cond_init(cond,NULL)) == 0) {
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/*
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* If the condvar was statically allocated, properly
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* initialize the tail queue.
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*/
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if (((*cond)->c_flags & COND_FLAGS_INITED) == 0) {
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TAILQ_INIT(&(*cond)->c_queue);
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(*cond)->c_flags |= COND_FLAGS_INITED;
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}
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/* Lock the condition variable structure: */
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_SPINLOCK(&(*cond)->lock);
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/* Process according to condition variable type: */
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switch ((*cond)->c_type) {
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/* Fast condition variable: */
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case COND_TYPE_FAST:
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if ((mutex == NULL) || (((*cond)->c_mutex != NULL) &&
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((*cond)->c_mutex != *mutex))) {
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/* Return invalid argument error: */
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rval = EINVAL;
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/* Unlock the condition variable structure: */
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_SPINUNLOCK(&(*cond)->lock);
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} else {
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/* Set the wakeup time: */
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_thread_run->wakeup_time.tv_sec =
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abstime->tv_sec;
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_thread_run->wakeup_time.tv_nsec =
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abstime->tv_nsec;
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/* Reset the timeout flag: */
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_thread_run->timeout = 0;
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/*
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* Queue the running thread for the condition
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* variable:
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*/
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cond_queue_enq(*cond, _thread_run);
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/* Remember the mutex that is being used: */
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(*cond)->c_mutex = *mutex;
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/* Unlock the mutex: */
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if ((rval = _mutex_cv_unlock(mutex)) != 0) {
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/*
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* Cannot unlock the mutex, so remove
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* the running thread from the condition
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* variable queue:
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*/
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cond_queue_remove(*cond, _thread_run);
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/* Check for no more waiters: */
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if (TAILQ_FIRST(&(*cond)->c_queue) == NULL)
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(*cond)->c_mutex = NULL;
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/* Unlock the condition variable structure: */
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_SPINUNLOCK(&(*cond)->lock);
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} else {
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/*
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* Schedule the next thread and unlock
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* the condition variable structure:
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*/
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_thread_kern_sched_state_unlock(PS_COND_WAIT,
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&(*cond)->lock, __FILE__, __LINE__);
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/* Check if the wait timedout: */
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if (_thread_run->timeout == 0) {
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/* Lock the mutex: */
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rval = _mutex_cv_lock(mutex);
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}
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else {
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/* Lock the condition variable structure: */
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_SPINLOCK(&(*cond)->lock);
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/*
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* The wait timed out; remove
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* the thread from the condition
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* variable queue:
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*/
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cond_queue_remove(*cond,
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_thread_run);
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/* Check for no more waiters: */
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if (TAILQ_FIRST(&(*cond)->c_queue) == NULL)
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(*cond)->c_mutex = NULL;
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/* Unock the condition variable structure: */
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_SPINUNLOCK(&(*cond)->lock);
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/* Return a timeout error: */
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rval = ETIMEDOUT;
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/*
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* Lock the mutex and ignore
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* any errors:
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*/
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(void)_mutex_cv_lock(mutex);
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}
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}
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}
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break;
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/* Trap invalid condition variable types: */
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default:
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/* Unlock the condition variable structure: */
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_SPINUNLOCK(&(*cond)->lock);
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/* Return an invalid argument error: */
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rval = EINVAL;
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break;
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}
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}
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/* Return the completion status: */
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return (rval);
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}
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int
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pthread_cond_signal(pthread_cond_t * cond)
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{
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int rval = 0;
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pthread_t pthread;
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if (cond == NULL || *cond == NULL)
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rval = EINVAL;
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else {
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/* Lock the condition variable structure: */
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_SPINLOCK(&(*cond)->lock);
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/* Process according to condition variable type: */
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switch ((*cond)->c_type) {
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/* Fast condition variable: */
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case COND_TYPE_FAST:
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/*
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* Enter a loop to dequeue threads from the condition
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* queue until we find one that hasn't previously
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* timed out.
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*/
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while (((pthread = cond_queue_deq(*cond)) != NULL) &&
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(pthread->timeout != 0)) {
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}
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if (pthread != NULL)
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/* Allow the thread to run: */
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PTHREAD_NEW_STATE(pthread,PS_RUNNING);
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/* Check for no more waiters: */
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if (TAILQ_FIRST(&(*cond)->c_queue) == NULL)
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(*cond)->c_mutex = NULL;
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break;
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/* Trap invalid condition variable types: */
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default:
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/* Return an invalid argument error: */
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rval = EINVAL;
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break;
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}
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/* Unlock the condition variable structure: */
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_SPINUNLOCK(&(*cond)->lock);
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}
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/* Return the completion status: */
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return (rval);
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}
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int
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pthread_cond_broadcast(pthread_cond_t * cond)
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{
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int rval = 0;
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pthread_t pthread;
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if (cond == NULL || *cond == NULL)
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rval = EINVAL;
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else {
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/*
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* Guard against preemption by a scheduling signal.
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* A change of thread state modifies the waiting
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* and priority queues. In addition, we must assure
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* that all threads currently waiting on the condition
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* variable are signaled and are not timedout by a
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* scheduling signal that causes a preemption.
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*/
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_thread_kern_sched_defer();
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/* Lock the condition variable structure: */
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_SPINLOCK(&(*cond)->lock);
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/* Process according to condition variable type: */
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switch ((*cond)->c_type) {
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/* Fast condition variable: */
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case COND_TYPE_FAST:
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/*
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* Enter a loop to bring all threads off the
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* condition queue:
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*/
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while ((pthread = cond_queue_deq(*cond)) != NULL) {
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/*
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* The thread is already running if the
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* timeout flag is set.
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*/
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if (pthread->timeout == 0)
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PTHREAD_NEW_STATE(pthread,PS_RUNNING);
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}
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/* There are no more waiting threads: */
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(*cond)->c_mutex = NULL;
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break;
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/* Trap invalid condition variable types: */
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default:
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/* Return an invalid argument error: */
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rval = EINVAL;
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break;
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}
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/* Unlock the condition variable structure: */
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_SPINUNLOCK(&(*cond)->lock);
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/* Reenable preemption and yield if necessary.
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*/
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_thread_kern_sched_undefer();
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}
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/* Return the completion status: */
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return (rval);
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}
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/*
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* Dequeue a waiting thread from the head of a condition queue in
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* descending priority order.
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*/
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static inline pthread_t
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cond_queue_deq(pthread_cond_t cond)
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{
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pthread_t pthread;
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if ((pthread = TAILQ_FIRST(&cond->c_queue)) != NULL) {
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TAILQ_REMOVE(&cond->c_queue, pthread, qe);
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pthread->flags &= ~PTHREAD_FLAGS_QUEUED;
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}
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return(pthread);
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}
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/*
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* Remove a waiting thread from a condition queue in descending priority
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* order.
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*/
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static inline void
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cond_queue_remove(pthread_cond_t cond, pthread_t pthread)
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{
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/*
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* Because pthread_cond_timedwait() can timeout as well
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* as be signaled by another thread, it is necessary to
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* guard against removing the thread from the queue if
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* it isn't in the queue.
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*/
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if (pthread->flags & PTHREAD_FLAGS_QUEUED) {
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TAILQ_REMOVE(&cond->c_queue, pthread, qe);
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pthread->flags &= ~PTHREAD_FLAGS_QUEUED;
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}
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}
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/*
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* Enqueue a waiting thread to a condition queue in descending priority
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* order.
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*/
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static inline void
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cond_queue_enq(pthread_cond_t cond, pthread_t pthread)
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{
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pthread_t tid = TAILQ_LAST(&cond->c_queue, cond_head);
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/*
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* For the common case of all threads having equal priority,
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* we perform a quick check against the priority of the thread
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* at the tail of the queue.
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*/
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if ((tid == NULL) || (pthread->active_priority <= tid->active_priority))
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TAILQ_INSERT_TAIL(&cond->c_queue, pthread, qe);
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else {
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tid = TAILQ_FIRST(&cond->c_queue);
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while (pthread->active_priority <= tid->active_priority)
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tid = TAILQ_NEXT(tid, qe);
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TAILQ_INSERT_BEFORE(tid, pthread, qe);
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}
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pthread->flags |= PTHREAD_FLAGS_QUEUED;
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}
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#endif
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