367 lines
11 KiB
C
367 lines
11 KiB
C
/* Linuxthreads - a simple clone()-based implementation of Posix */
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/* threads for Linux. */
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/* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr) */
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/* */
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/* This program is free software; you can redistribute it and/or */
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/* modify it under the terms of the GNU Library General Public License */
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/* as published by the Free Software Foundation; either version 2 */
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/* of the License, or (at your option) any later version. */
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/* */
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/* This program is distributed in the hope that it will be useful, */
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/* but WITHOUT ANY WARRANTY; without even the implied warranty of */
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/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the */
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/* GNU Library General Public License for more details. */
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/* Mutexes */
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#include <bits/libc-lock.h>
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#include <errno.h>
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#include <sched.h>
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#include <stddef.h>
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#include <limits.h>
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#include "pthread.h"
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#include "internals.h"
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#include "spinlock.h"
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#include "queue.h"
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#include "restart.h"
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int __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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__pthread_init_lock(&mutex->__m_lock);
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mutex->__m_kind =
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mutex_attr == NULL ? PTHREAD_MUTEX_TIMED_NP : mutex_attr->__mutexkind;
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mutex->__m_count = 0;
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mutex->__m_owner = NULL;
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return 0;
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}
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strong_alias (__pthread_mutex_init, pthread_mutex_init)
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int __pthread_mutex_destroy(pthread_mutex_t * mutex)
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{
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switch (mutex->__m_kind) {
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case PTHREAD_MUTEX_ADAPTIVE_NP:
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case PTHREAD_MUTEX_RECURSIVE_NP:
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if ((mutex->__m_lock.__status & 1) != 0)
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return EBUSY;
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return 0;
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case PTHREAD_MUTEX_ERRORCHECK_NP:
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case PTHREAD_MUTEX_TIMED_NP:
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if (mutex->__m_lock.__status != 0)
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return EBUSY;
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return 0;
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default:
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return EINVAL;
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}
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}
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strong_alias (__pthread_mutex_destroy, pthread_mutex_destroy)
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int __pthread_mutex_trylock(pthread_mutex_t * mutex)
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{
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pthread_descr self;
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int retcode;
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switch(mutex->__m_kind) {
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case PTHREAD_MUTEX_ADAPTIVE_NP:
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retcode = __pthread_trylock(&mutex->__m_lock);
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return retcode;
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case PTHREAD_MUTEX_RECURSIVE_NP:
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self = thread_self();
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if (mutex->__m_owner == self) {
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mutex->__m_count++;
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return 0;
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}
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retcode = __pthread_trylock(&mutex->__m_lock);
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if (retcode == 0) {
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mutex->__m_owner = self;
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mutex->__m_count = 0;
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}
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return retcode;
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case PTHREAD_MUTEX_ERRORCHECK_NP:
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retcode = __pthread_alt_trylock(&mutex->__m_lock);
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if (retcode == 0) {
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mutex->__m_owner = thread_self();
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}
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return retcode;
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case PTHREAD_MUTEX_TIMED_NP:
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retcode = __pthread_alt_trylock(&mutex->__m_lock);
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return retcode;
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default:
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return EINVAL;
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}
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}
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strong_alias (__pthread_mutex_trylock, pthread_mutex_trylock)
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int __pthread_mutex_lock(pthread_mutex_t * mutex)
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{
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pthread_descr self;
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switch(mutex->__m_kind) {
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case PTHREAD_MUTEX_ADAPTIVE_NP:
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__pthread_lock(&mutex->__m_lock, NULL);
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return 0;
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case PTHREAD_MUTEX_RECURSIVE_NP:
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self = thread_self();
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if (mutex->__m_owner == self) {
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mutex->__m_count++;
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return 0;
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}
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__pthread_lock(&mutex->__m_lock, self);
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mutex->__m_owner = self;
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mutex->__m_count = 0;
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return 0;
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case PTHREAD_MUTEX_ERRORCHECK_NP:
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self = thread_self();
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if (mutex->__m_owner == self) return EDEADLK;
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__pthread_alt_lock(&mutex->__m_lock, self);
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mutex->__m_owner = self;
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return 0;
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case PTHREAD_MUTEX_TIMED_NP:
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__pthread_alt_lock(&mutex->__m_lock, NULL);
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return 0;
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default:
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return EINVAL;
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}
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}
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strong_alias (__pthread_mutex_lock, pthread_mutex_lock)
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int __pthread_mutex_timedlock (pthread_mutex_t *mutex,
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const struct timespec *abstime)
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{
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pthread_descr self;
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int res;
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if (__builtin_expect (abstime->tv_nsec, 0) < 0
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|| __builtin_expect (abstime->tv_nsec, 0) >= 1000000000)
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return EINVAL;
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switch(mutex->__m_kind) {
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case PTHREAD_MUTEX_ADAPTIVE_NP:
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__pthread_lock(&mutex->__m_lock, NULL);
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return 0;
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case PTHREAD_MUTEX_RECURSIVE_NP:
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self = thread_self();
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if (mutex->__m_owner == self) {
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mutex->__m_count++;
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return 0;
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}
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__pthread_lock(&mutex->__m_lock, self);
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mutex->__m_owner = self;
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mutex->__m_count = 0;
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return 0;
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case PTHREAD_MUTEX_ERRORCHECK_NP:
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self = thread_self();
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if (mutex->__m_owner == self) return EDEADLK;
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res = __pthread_alt_timedlock(&mutex->__m_lock, self, abstime);
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if (res != 0)
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{
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mutex->__m_owner = self;
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return 0;
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}
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return ETIMEDOUT;
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case PTHREAD_MUTEX_TIMED_NP:
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/* Only this type supports timed out lock. */
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return (__pthread_alt_timedlock(&mutex->__m_lock, NULL, abstime)
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? 0 : ETIMEDOUT);
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default:
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return EINVAL;
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}
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}
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strong_alias (__pthread_mutex_timedlock, pthread_mutex_timedlock)
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int __pthread_mutex_unlock(pthread_mutex_t * mutex)
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{
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switch (mutex->__m_kind) {
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case PTHREAD_MUTEX_ADAPTIVE_NP:
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__pthread_unlock(&mutex->__m_lock);
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return 0;
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case PTHREAD_MUTEX_RECURSIVE_NP:
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if (mutex->__m_owner != thread_self())
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return EPERM;
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if (mutex->__m_count > 0) {
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mutex->__m_count--;
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return 0;
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}
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mutex->__m_owner = NULL;
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__pthread_unlock(&mutex->__m_lock);
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return 0;
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case PTHREAD_MUTEX_ERRORCHECK_NP:
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if (mutex->__m_owner != thread_self() || mutex->__m_lock.__status == 0)
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return EPERM;
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mutex->__m_owner = NULL;
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__pthread_alt_unlock(&mutex->__m_lock);
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return 0;
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case PTHREAD_MUTEX_TIMED_NP:
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__pthread_alt_unlock(&mutex->__m_lock);
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return 0;
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default:
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return EINVAL;
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}
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}
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strong_alias (__pthread_mutex_unlock, pthread_mutex_unlock)
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int __pthread_mutexattr_init(pthread_mutexattr_t *attr)
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{
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attr->__mutexkind = PTHREAD_MUTEX_TIMED_NP;
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return 0;
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}
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strong_alias (__pthread_mutexattr_init, pthread_mutexattr_init)
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int __pthread_mutexattr_destroy(pthread_mutexattr_t *attr)
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{
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return 0;
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}
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strong_alias (__pthread_mutexattr_destroy, pthread_mutexattr_destroy)
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int __pthread_mutexattr_settype(pthread_mutexattr_t *attr, int kind)
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{
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if (kind != PTHREAD_MUTEX_ADAPTIVE_NP
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&& kind != PTHREAD_MUTEX_RECURSIVE_NP
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&& kind != PTHREAD_MUTEX_ERRORCHECK_NP
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&& kind != PTHREAD_MUTEX_TIMED_NP)
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return EINVAL;
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attr->__mutexkind = kind;
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return 0;
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}
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weak_alias (__pthread_mutexattr_settype, pthread_mutexattr_settype)
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#if !defined(_ELIX_LEVEL) || _ELIX_LEVEL >= 2
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strong_alias ( __pthread_mutexattr_settype, __pthread_mutexattr_setkind_np)
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weak_alias (__pthread_mutexattr_setkind_np, pthread_mutexattr_setkind_np)
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#endif /* !_ELIX_LEVEL || _ELIX_LEVEL >= 2 */
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int __pthread_mutexattr_gettype(const pthread_mutexattr_t *attr, int *kind)
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{
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*kind = attr->__mutexkind;
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return 0;
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}
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weak_alias (__pthread_mutexattr_gettype, pthread_mutexattr_gettype)
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#if !defined(_ELIX_LEVEL) || _ELIX_LEVEL >= 2
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strong_alias (__pthread_mutexattr_gettype, __pthread_mutexattr_getkind_np)
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weak_alias (__pthread_mutexattr_getkind_np, pthread_mutexattr_getkind_np)
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#endif /* !_ELIX_LEVEL || _ELIX_LEVEL >= 2 */
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#if !defined(_ELIX_LEVEL) || _ELIX_LEVEL >= 3
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int __pthread_mutexattr_getpshared (const pthread_mutexattr_t *attr,
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int *pshared)
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{
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*pshared = PTHREAD_PROCESS_PRIVATE;
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return 0;
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}
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weak_alias (__pthread_mutexattr_getpshared, pthread_mutexattr_getpshared)
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int __pthread_mutexattr_setpshared (pthread_mutexattr_t *attr, int pshared)
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{
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if (pshared != PTHREAD_PROCESS_PRIVATE && pshared != PTHREAD_PROCESS_SHARED)
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return EINVAL;
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/* For now it is not possible to shared a conditional variable. */
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if (pshared != PTHREAD_PROCESS_PRIVATE)
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return ENOSYS;
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return 0;
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}
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weak_alias (__pthread_mutexattr_setpshared, pthread_mutexattr_setpshared)
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#endif /* !_ELIX_LEVEL || _ELIX_LEVEL >= 3 */
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/* Once-only execution */
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static pthread_mutex_t once_masterlock = PTHREAD_MUTEX_INITIALIZER;
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static pthread_cond_t once_finished = PTHREAD_COND_INITIALIZER;
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static int fork_generation = 0; /* Child process increments this after fork. */
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enum { NEVER = 0, IN_PROGRESS = 1, DONE = 2 };
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/* If a thread is canceled while calling the init_routine out of
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pthread once, this handler will reset the once_control variable
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to the NEVER state. */
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static void pthread_once_cancelhandler(void *arg)
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{
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pthread_once_t *once_control = arg;
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pthread_mutex_lock(&once_masterlock);
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*once_control = NEVER;
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pthread_mutex_unlock(&once_masterlock);
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pthread_cond_broadcast(&once_finished);
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}
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int __pthread_once(pthread_once_t * once_control, void (*init_routine)(void))
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{
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/* flag for doing the condition broadcast outside of mutex */
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int state_changed;
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/* Test without locking first for speed */
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if (*once_control == DONE) {
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READ_MEMORY_BARRIER();
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return 0;
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}
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/* Lock and test again */
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state_changed = 0;
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pthread_mutex_lock(&once_masterlock);
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/* If this object was left in an IN_PROGRESS state in a parent
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process (indicated by stale generation field), reset it to NEVER. */
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if ((*once_control & 3) == IN_PROGRESS && (*once_control & ~3) != fork_generation)
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*once_control = NEVER;
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/* If init_routine is being called from another routine, wait until
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it completes. */
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while ((*once_control & 3) == IN_PROGRESS) {
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pthread_cond_wait(&once_finished, &once_masterlock);
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}
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/* Here *once_control is stable and either NEVER or DONE. */
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if (*once_control == NEVER) {
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*once_control = IN_PROGRESS | fork_generation;
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pthread_mutex_unlock(&once_masterlock);
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pthread_cleanup_push(pthread_once_cancelhandler, once_control);
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init_routine();
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pthread_cleanup_pop(0);
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pthread_mutex_lock(&once_masterlock);
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WRITE_MEMORY_BARRIER();
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*once_control = DONE;
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state_changed = 1;
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}
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pthread_mutex_unlock(&once_masterlock);
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if (state_changed)
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pthread_cond_broadcast(&once_finished);
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return 0;
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}
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strong_alias (__pthread_once, pthread_once)
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/*
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* Handle the state of the pthread_once mechanism across forks. The
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* once_masterlock is acquired in the parent process prior to a fork to ensure
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* that no thread is in the critical region protected by the lock. After the
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* fork, the lock is released. In the child, the lock and the condition
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* variable are simply reset. The child also increments its generation
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* counter which lets pthread_once calls detect stale IN_PROGRESS states
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* and reset them back to NEVER.
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*/
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void __pthread_once_fork_prepare(void)
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{
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pthread_mutex_lock(&once_masterlock);
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}
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void __pthread_once_fork_parent(void)
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{
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pthread_mutex_unlock(&once_masterlock);
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}
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void __pthread_once_fork_child(void)
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{
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pthread_mutex_init(&once_masterlock, NULL);
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pthread_cond_init(&once_finished, NULL);
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if (fork_generation <= INT_MAX - 4)
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fork_generation += 4; /* leave least significant two bits zero */
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else
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fork_generation = 0;
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}
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