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/* Linuxthreads - a simple clone()-based implementation of Posix */
/* threads for Linux. */
/* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr) */
/* and Pavel Krauz (krauz@fsid.cvut.cz). */
/* */
/* This program is free software; you can redistribute it and/or */
/* modify it under the terms of the GNU Library General Public License */
/* as published by the Free Software Foundation; either version 2 */
/* of the License, or (at your option) any later version. */
/* */
/* This program is distributed in the hope that it will be useful, */
/* but WITHOUT ANY WARRANTY; without even the implied warranty of */
/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the */
/* GNU Library General Public License for more details. */
/* Condition variables */
#include <errno.h>
#include <sched.h>
#include <stddef.h>
#include <sys/time.h>
#include "pthread.h"
#include "internals.h"
#include "spinlock.h"
#include "queue.h"
#include "restart.h"
int pthread_cond_init(pthread_cond_t *cond,
const pthread_condattr_t *cond_attr)
{
__pthread_init_lock(&cond->__c_lock);
cond->__c_waiting = NULL;
return 0;
}
int pthread_cond_destroy(pthread_cond_t *cond)
{
if (cond->__c_waiting != NULL) return EBUSY;
return 0;
}
/* Function called by pthread_cancel to remove the thread from
waiting on a condition variable queue. */
static int cond_extricate_func(void *obj, pthread_descr th)
{
volatile pthread_descr self = thread_self();
pthread_cond_t *cond = obj;
int did_remove = 0;
__pthread_lock(&cond->__c_lock, self);
did_remove = remove_from_queue(&cond->__c_waiting, th);
__pthread_spin_unlock(&cond->__c_lock);
return did_remove;
}
int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
{
volatile pthread_descr self = thread_self();
pthread_extricate_if extr;
int already_canceled = 0;
/* Check whether the mutex is locked and owned by this thread. */
if (mutex->__m_kind != PTHREAD_MUTEX_FAST_NP && mutex->__m_owner != self)
return EINVAL;
/* Set up extrication interface */
extr.pu_object = cond;
extr.pu_extricate_func = cond_extricate_func;
/* Register extrication interface */
__pthread_set_own_extricate_if(self, &extr);
/* Atomically enqueue thread for waiting, but only if it is not
canceled. If the thread is canceled, then it will fall through the
suspend call below, and then call pthread_exit without
having to worry about whether it is still on the condition variable queue.
This depends on pthread_cancel setting p_canceled before calling the
extricate function. */
__pthread_lock(&cond->__c_lock, self);
if (!(THREAD_GETMEM(self, p_canceled)
&& THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE))
enqueue(&cond->__c_waiting, self);
else
already_canceled = 1;
__pthread_spin_unlock(&cond->__c_lock);
if (already_canceled) {
__pthread_set_own_extricate_if(self, 0);
pthread_exit(PTHREAD_CANCELED);
}
pthread_mutex_unlock(mutex);
suspend(self);
__pthread_set_own_extricate_if(self, 0);
/* Check for cancellation again, to provide correct cancellation
point behavior */
if (THREAD_GETMEM(self, p_woken_by_cancel)
&& THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) {
THREAD_SETMEM(self, p_woken_by_cancel, 0);
pthread_mutex_lock(mutex);
pthread_exit(PTHREAD_CANCELED);
}
pthread_mutex_lock(mutex);
return 0;
}
static int
pthread_cond_timedwait_relative(pthread_cond_t *cond,
pthread_mutex_t *mutex,
const struct timespec * abstime)
{
volatile pthread_descr self = thread_self();
int already_canceled = 0;
pthread_extricate_if extr;
/* Check whether the mutex is locked and owned by this thread. */
if (mutex->__m_owner != self)
return EINVAL;
already_canceled = 0;
/* Set up extrication interface */
extr.pu_object = cond;
extr.pu_extricate_func = cond_extricate_func;
/* Register extrication interface */
__pthread_set_own_extricate_if(self, &extr);
/* Enqueue to wait on the condition and check for cancellation. */
__pthread_lock(&cond->__c_lock, self);
if (!(THREAD_GETMEM(self, p_canceled)
&& THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE))
enqueue(&cond->__c_waiting, self);
else
already_canceled = 1;
__pthread_spin_unlock(&cond->__c_lock);
if (already_canceled) {
__pthread_set_own_extricate_if(self, 0);
pthread_exit(PTHREAD_CANCELED);
}
pthread_mutex_unlock(mutex);
if (!timedsuspend(self, abstime) == 0) {
int was_on_queue;
/* __pthread_lock will queue back any spurious restarts that
may happen to it. */
__pthread_lock(&cond->__c_lock, self);
was_on_queue = remove_from_queue(&cond->__c_waiting, self);
__pthread_spin_unlock(&cond->__c_lock);
if (was_on_queue) {
__pthread_set_own_extricate_if(self, 0);
pthread_mutex_lock(mutex);
return ETIMEDOUT;
}
/* Eat the outstanding restart() from the signaller */
suspend(self);
}
__pthread_set_own_extricate_if(self, 0);
/* The remaining logic is the same as in other cancellable waits,
such as pthread_join sem_wait or pthread_cond wait. */
if (THREAD_GETMEM(self, p_woken_by_cancel)
&& THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) {
THREAD_SETMEM(self, p_woken_by_cancel, 0);
pthread_mutex_lock(mutex);
pthread_exit(PTHREAD_CANCELED);
}
pthread_mutex_lock(mutex);
return 0;
}
int pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
const struct timespec * abstime)
{
/* Indirect call through pointer! */
return pthread_cond_timedwait_relative(cond, mutex, abstime);
}
int pthread_cond_signal(pthread_cond_t *cond)
{
pthread_descr th;
__pthread_lock(&cond->__c_lock, NULL);
th = dequeue(&cond->__c_waiting);
__pthread_spin_unlock(&cond->__c_lock);
if (th != NULL) restart(th);
return 0;
}
int pthread_cond_broadcast(pthread_cond_t *cond)
{
pthread_descr tosignal, th;
__pthread_lock(&cond->__c_lock, NULL);
/* Copy the current state of the waiting queue and empty it */
tosignal = cond->__c_waiting;
cond->__c_waiting = NULL;
__pthread_spin_unlock(&cond->__c_lock);
/* Now signal each process in the queue */
while ((th = dequeue(&tosignal)) != NULL) restart(th);
return 0;
}
int pthread_condattr_init(pthread_condattr_t *attr)
{
return 0;
}
int pthread_condattr_destroy(pthread_condattr_t *attr)
{
return 0;
}
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