302 lines
8.5 KiB
C
302 lines
8.5 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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/* and Pavel Krauz (krauz@fsid.cvut.cz). */
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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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/* Condition variables */
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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 <sys/time.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_cond_init(pthread_cond_t *cond,
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const pthread_condattr_t *cond_attr)
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{
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__pthread_init_lock(&cond->__c_lock);
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cond->__c_waiting = NULL;
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return 0;
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}
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int pthread_cond_destroy(pthread_cond_t *cond)
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{
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if (cond->__c_waiting != NULL) return EBUSY;
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return 0;
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}
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/* Function called by pthread_cancel to remove the thread from
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waiting on a condition variable queue. */
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static int cond_extricate_func(void *obj, pthread_descr th)
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{
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volatile pthread_descr self = thread_self();
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pthread_cond_t *cond = obj;
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int did_remove = 0;
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__pthread_lock(&cond->__c_lock, self);
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did_remove = remove_from_queue(&cond->__c_waiting, th);
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__pthread_unlock(&cond->__c_lock);
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return did_remove;
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}
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int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
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{
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volatile pthread_descr self = thread_self();
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pthread_extricate_if extr;
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int already_canceled = 0;
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int spurious_wakeup_count;
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/* Check whether the mutex is locked and owned by this thread. */
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if (mutex->__m_kind != PTHREAD_MUTEX_TIMED_NP
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&& mutex->__m_kind != PTHREAD_MUTEX_ADAPTIVE_NP
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&& mutex->__m_owner != self)
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return EINVAL;
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/* Set up extrication interface */
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extr.pu_object = cond;
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extr.pu_extricate_func = cond_extricate_func;
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/* Register extrication interface */
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THREAD_SETMEM(self, p_condvar_avail, 0);
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__pthread_set_own_extricate_if(self, &extr);
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/* Atomically enqueue thread for waiting, but only if it is not
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canceled. If the thread is canceled, then it will fall through the
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suspend call below, and then call pthread_exit without
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having to worry about whether it is still on the condition variable queue.
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This depends on pthread_cancel setting p_canceled before calling the
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extricate function. */
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__pthread_lock(&cond->__c_lock, self);
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if (!(THREAD_GETMEM(self, p_canceled)
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&& THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE))
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enqueue(&cond->__c_waiting, self);
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else
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already_canceled = 1;
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__pthread_unlock(&cond->__c_lock);
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if (already_canceled) {
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__pthread_set_own_extricate_if(self, 0);
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__pthread_do_exit(PTHREAD_CANCELED, CURRENT_STACK_FRAME);
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}
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pthread_mutex_unlock(mutex);
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spurious_wakeup_count = 0;
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while (1)
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{
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suspend(self);
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if (THREAD_GETMEM(self, p_condvar_avail) == 0
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&& (THREAD_GETMEM(self, p_woken_by_cancel) == 0
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|| THREAD_GETMEM(self, p_cancelstate) != PTHREAD_CANCEL_ENABLE))
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{
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/* Count resumes that don't belong to us. */
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spurious_wakeup_count++;
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continue;
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}
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break;
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}
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__pthread_set_own_extricate_if(self, 0);
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/* Check for cancellation again, to provide correct cancellation
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point behavior */
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if (THREAD_GETMEM(self, p_woken_by_cancel)
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&& THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) {
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THREAD_SETMEM(self, p_woken_by_cancel, 0);
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pthread_mutex_lock(mutex);
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__pthread_do_exit(PTHREAD_CANCELED, CURRENT_STACK_FRAME);
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}
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/* Put back any resumes we caught that don't belong to us. */
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while (spurious_wakeup_count--)
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restart(self);
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pthread_mutex_lock(mutex);
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return 0;
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}
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static int
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pthread_cond_timedwait_relative(pthread_cond_t *cond,
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pthread_mutex_t *mutex,
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const struct timespec * abstime)
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{
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volatile pthread_descr self = thread_self();
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int already_canceled = 0;
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pthread_extricate_if extr;
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int spurious_wakeup_count;
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/* Check whether the mutex is locked and owned by this thread. */
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if (mutex->__m_kind != PTHREAD_MUTEX_TIMED_NP
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&& mutex->__m_kind != PTHREAD_MUTEX_ADAPTIVE_NP
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&& mutex->__m_owner != self)
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return EINVAL;
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/* Set up extrication interface */
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extr.pu_object = cond;
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extr.pu_extricate_func = cond_extricate_func;
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/* Register extrication interface */
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THREAD_SETMEM(self, p_condvar_avail, 0);
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__pthread_set_own_extricate_if(self, &extr);
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/* Enqueue to wait on the condition and check for cancellation. */
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__pthread_lock(&cond->__c_lock, self);
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if (!(THREAD_GETMEM(self, p_canceled)
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&& THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE))
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enqueue(&cond->__c_waiting, self);
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else
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already_canceled = 1;
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__pthread_unlock(&cond->__c_lock);
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if (already_canceled) {
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__pthread_set_own_extricate_if(self, 0);
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__pthread_do_exit(PTHREAD_CANCELED, CURRENT_STACK_FRAME);
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}
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pthread_mutex_unlock(mutex);
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spurious_wakeup_count = 0;
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while (1)
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{
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if (!timedsuspend(self, abstime)) {
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int was_on_queue;
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/* __pthread_lock will queue back any spurious restarts that
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may happen to it. */
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__pthread_lock(&cond->__c_lock, self);
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was_on_queue = remove_from_queue(&cond->__c_waiting, self);
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__pthread_unlock(&cond->__c_lock);
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if (was_on_queue) {
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__pthread_set_own_extricate_if(self, 0);
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pthread_mutex_lock(mutex);
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return ETIMEDOUT;
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}
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/* Eat the outstanding restart() from the signaller */
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suspend(self);
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}
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if (THREAD_GETMEM(self, p_condvar_avail) == 0
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&& (THREAD_GETMEM(self, p_woken_by_cancel) == 0
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|| THREAD_GETMEM(self, p_cancelstate) != PTHREAD_CANCEL_ENABLE))
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{
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/* Count resumes that don't belong to us. */
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spurious_wakeup_count++;
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continue;
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}
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break;
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}
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__pthread_set_own_extricate_if(self, 0);
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/* The remaining logic is the same as in other cancellable waits,
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such as pthread_join sem_wait or pthread_cond wait. */
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if (THREAD_GETMEM(self, p_woken_by_cancel)
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&& THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) {
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THREAD_SETMEM(self, p_woken_by_cancel, 0);
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pthread_mutex_lock(mutex);
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__pthread_do_exit(PTHREAD_CANCELED, CURRENT_STACK_FRAME);
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}
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/* Put back any resumes we caught that don't belong to us. */
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while (spurious_wakeup_count--)
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restart(self);
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pthread_mutex_lock(mutex);
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return 0;
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}
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int 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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/* Indirect call through pointer! */
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return pthread_cond_timedwait_relative(cond, mutex, abstime);
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}
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int pthread_cond_signal(pthread_cond_t *cond)
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{
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pthread_descr th;
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__pthread_lock(&cond->__c_lock, NULL);
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th = dequeue(&cond->__c_waiting);
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__pthread_unlock(&cond->__c_lock);
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if (th != NULL) {
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th->p_condvar_avail = 1;
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WRITE_MEMORY_BARRIER();
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restart(th);
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}
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return 0;
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}
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int pthread_cond_broadcast(pthread_cond_t *cond)
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{
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pthread_descr tosignal, th;
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__pthread_lock(&cond->__c_lock, NULL);
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/* Copy the current state of the waiting queue and empty it */
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tosignal = cond->__c_waiting;
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cond->__c_waiting = NULL;
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__pthread_unlock(&cond->__c_lock);
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/* Now signal each process in the queue */
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while ((th = dequeue(&tosignal)) != NULL) {
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th->p_condvar_avail = 1;
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WRITE_MEMORY_BARRIER();
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restart(th);
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}
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return 0;
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}
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int pthread_condattr_init(pthread_condattr_t *attr)
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{
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return 0;
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}
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int pthread_condattr_destroy(pthread_condattr_t *attr)
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{
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return 0;
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}
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#if !defined(_ELIX_LEVEL) || _ELIX_LEVEL >= 3
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int pthread_condattr_getpshared (const pthread_condattr_t *attr, 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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int pthread_condattr_setpshared (pthread_condattr_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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#endif /* !_ELIX_LEVEL || _ELIX_LEVEL >= 3 */
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