4a027d50c7
for the process, not a separate set for each thread). By default, the process now only has signal handlers installed for SIGVTALRM, SIGINFO and SIGCHLD. The thread kernel signal handler is installed for other signals on demand. This means that SIG_IGN and SIG_DFL processing is now left to the kernel, not the thread kernel. Change the signal dispatch to no longer use a signal thread, and call the signal handler using the stack of the thread that has the signal pending. Change the atomic lock method to use test-and-set asm code with a yield if blocked. This introduces separate locks for each type of object instead of blocking signals to prevent a context switch. It was this blocking of signals that caused the performance degradation the people have noted. This is a *big* change!
372 lines
9.5 KiB
C
372 lines
9.5 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 REGENTS 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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#ifdef _THREAD_SAFE
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#include <pthread.h>
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#include "pthread_private.h"
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int
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pthread_mutex_init(pthread_mutex_t * mutex,
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const pthread_mutexattr_t * mutex_attr)
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{
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enum pthread_mutextype type;
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pthread_mutex_t pmutex;
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int ret = 0;
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int status;
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if (mutex == NULL) {
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ret = EINVAL;
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} else {
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/* Check if default mutex attributes: */
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if (mutex_attr == NULL || *mutex_attr == NULL)
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/* Default to a fast mutex: */
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type = MUTEX_TYPE_FAST;
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else if ((*mutex_attr)->m_type >= MUTEX_TYPE_MAX)
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/* Return an invalid argument error: */
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ret = EINVAL;
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else
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/* Use the requested mutex type: */
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type = (*mutex_attr)->m_type;
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/* Check no errors so far: */
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if (ret == 0) {
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if ((pmutex = (pthread_mutex_t)
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malloc(sizeof(struct pthread_mutex))) == NULL)
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ret = ENOMEM;
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else {
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/* Reset the mutex flags: */
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pmutex->m_flags = 0;
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/* Process according to mutex type: */
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switch (type) {
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/* Fast mutex: */
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case MUTEX_TYPE_FAST:
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/* Nothing to do here. */
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break;
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/* Counting mutex: */
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case MUTEX_TYPE_COUNTING_FAST:
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/* Reset the mutex count: */
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pmutex->m_data.m_count = 0;
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break;
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/* Trap invalid mutex types: */
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default:
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/* Return an invalid argument error: */
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ret = EINVAL;
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break;
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}
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if (ret == 0) {
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/* Initialise the rest of the mutex: */
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_thread_queue_init(&pmutex->m_queue);
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pmutex->m_flags |= MUTEX_FLAGS_INITED;
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pmutex->m_owner = NULL;
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pmutex->m_type = type;
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pmutex->access_lock = 0;
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*mutex = pmutex;
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} else {
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free(pmutex);
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*mutex = NULL;
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}
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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 (ret);
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}
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int
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pthread_mutex_destroy(pthread_mutex_t * mutex)
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{
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int ret = 0;
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if (mutex == NULL || *mutex == NULL)
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ret = EINVAL;
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else {
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/* Lock the mutex structure: */
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_spinlock(&(*mutex)->access_lock);
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/*
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* Free the memory allocated for the mutex
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* structure:
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*/
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free(*mutex);
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/*
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* Leave the caller's pointer NULL now that
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* the mutex has been destroyed:
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*/
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*mutex = NULL;
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}
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/* Return the completion status: */
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return (ret);
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}
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int
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pthread_mutex_trylock(pthread_mutex_t * mutex)
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{
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int ret = 0;
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if (mutex == NULL)
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ret = EINVAL;
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/*
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* If the mutex is statically initialized, perform the dynamic
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* initialization:
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*/
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else if (*mutex != NULL ||
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(ret = pthread_mutex_init(mutex,NULL)) == 0) {
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/* Lock the mutex structure: */
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_spinlock(&(*mutex)->access_lock);
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/* Process according to mutex type: */
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switch ((*mutex)->m_type) {
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/* Fast mutex: */
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case MUTEX_TYPE_FAST:
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/* Check if this mutex is not locked: */
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if ((*mutex)->m_owner == NULL) {
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/* Lock the mutex for the running thread: */
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(*mutex)->m_owner = _thread_run;
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} else {
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/* Return a busy error: */
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ret = EBUSY;
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}
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break;
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/* Counting mutex: */
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case MUTEX_TYPE_COUNTING_FAST:
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/* Check if this mutex is locked: */
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if ((*mutex)->m_owner != NULL) {
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/*
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* Check if the mutex is locked by the running
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* thread:
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*/
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if ((*mutex)->m_owner == _thread_run) {
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/* Increment the lock count: */
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(*mutex)->m_data.m_count++;
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} else {
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/* Return a busy error: */
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ret = EBUSY;
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}
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} else {
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/* Lock the mutex for the running thread: */
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(*mutex)->m_owner = _thread_run;
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}
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break;
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/* Trap invalid mutex types: */
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default:
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/* Return an invalid argument error: */
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ret = EINVAL;
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break;
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}
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/* Unlock the mutex structure: */
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_atomic_unlock(&(*mutex)->access_lock);
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}
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/* Return the completion status: */
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return (ret);
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}
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int
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pthread_mutex_lock(pthread_mutex_t * mutex)
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{
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int ret = 0;
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if (mutex == NULL)
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ret = EINVAL;
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/*
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* If the mutex is statically initialized, perform the dynamic
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* initialization:
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*/
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else if (*mutex != NULL ||
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(ret = pthread_mutex_init(mutex,NULL)) == 0) {
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/* Lock the mutex structure: */
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_spinlock(&(*mutex)->access_lock);
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/* Process according to mutex type: */
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switch ((*mutex)->m_type) {
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/* Fast mutexes do not check for any error conditions: */
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case MUTEX_TYPE_FAST:
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/*
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* Enter a loop to wait for the mutex to be locked by the
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* current thread:
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*/
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while ((*mutex)->m_owner != _thread_run) {
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/* Check if the mutex is not locked: */
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if ((*mutex)->m_owner == NULL) {
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/* Lock the mutex for this thread: */
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(*mutex)->m_owner = _thread_run;
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} else {
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/*
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* Join the queue of threads waiting to lock
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* the mutex:
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*/
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_thread_queue_enq(&(*mutex)->m_queue, _thread_run);
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/* Unlock the mutex structure: */
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_atomic_unlock(&(*mutex)->access_lock);
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/* Block signals: */
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_thread_kern_sched_state(PS_MUTEX_WAIT, __FILE__, __LINE__);
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/* Lock the mutex again: */
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_spinlock(&(*mutex)->access_lock);
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}
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}
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break;
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/* Counting mutex: */
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case MUTEX_TYPE_COUNTING_FAST:
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/*
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* Enter a loop to wait for the mutex to be locked by the
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* current thread:
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*/
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while ((*mutex)->m_owner != _thread_run) {
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/* Check if the mutex is not locked: */
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if ((*mutex)->m_owner == NULL) {
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/* Lock the mutex for this thread: */
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(*mutex)->m_owner = _thread_run;
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/* Reset the lock count for this mutex: */
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(*mutex)->m_data.m_count = 0;
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} else {
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/*
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* Join the queue of threads waiting to lock
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* the mutex:
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*/
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_thread_queue_enq(&(*mutex)->m_queue, _thread_run);
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/* Unlock the mutex structure: */
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_atomic_unlock(&(*mutex)->access_lock);
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/* Block signals: */
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_thread_kern_sched_state(PS_MUTEX_WAIT, __FILE__, __LINE__);
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/* Lock the mutex again: */
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_spinlock(&(*mutex)->access_lock);
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}
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}
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/* Increment the lock count for this mutex: */
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(*mutex)->m_data.m_count++;
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break;
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/* Trap invalid mutex types: */
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default:
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/* Return an invalid argument error: */
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ret = EINVAL;
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break;
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}
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/* Unlock the mutex structure: */
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_atomic_unlock(&(*mutex)->access_lock);
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}
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/* Return the completion status: */
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return (ret);
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}
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int
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pthread_mutex_unlock(pthread_mutex_t * mutex)
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{
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int ret = 0;
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if (mutex == NULL || *mutex == NULL) {
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ret = EINVAL;
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} else {
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/* Lock the mutex structure: */
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_spinlock(&(*mutex)->access_lock);
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/* Process according to mutex type: */
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switch ((*mutex)->m_type) {
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/* Fast mutexes do not check for any error conditions: */
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case MUTEX_TYPE_FAST:
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/* Check if the running thread is not the owner of the mutex: */
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if ((*mutex)->m_owner != _thread_run) {
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/* Return an invalid argument error: */
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ret = EINVAL;
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}
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/*
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* Get the next thread from the queue of threads waiting on
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* the mutex:
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*/
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else if (((*mutex)->m_owner = _thread_queue_deq(&(*mutex)->m_queue)) != NULL) {
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/* Allow the new owner of the mutex to run: */
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PTHREAD_NEW_STATE((*mutex)->m_owner,PS_RUNNING);
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}
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break;
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/* Counting mutex: */
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case MUTEX_TYPE_COUNTING_FAST:
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/* Check if the running thread is not the owner of the mutex: */
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if ((*mutex)->m_owner != _thread_run) {
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/* Return an invalid argument error: */
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ret = EINVAL;
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}
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/* Check if there are still counts: */
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else if ((*mutex)->m_data.m_count) {
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/* Decrement the count: */
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(*mutex)->m_data.m_count--;
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}
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/*
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* Get the next thread from the queue of threads waiting on
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* the mutex:
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*/
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else if (((*mutex)->m_owner = _thread_queue_deq(&(*mutex)->m_queue)) != NULL) {
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/* Allow the new owner of the mutex to run: */
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PTHREAD_NEW_STATE((*mutex)->m_owner,PS_RUNNING);
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}
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break;
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/* Trap invalid mutex types: */
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default:
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/* Return an invalid argument error: */
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ret = EINVAL;
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break;
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}
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/* Unlock the mutex structure: */
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_atomic_unlock(&(*mutex)->access_lock);
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}
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/* Return the completion status: */
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return (ret);
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}
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#endif
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