root / prex-0.9.0 / sys / sync / cond.c @ 03e9c04a
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/*-
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* Copyright (c) 2005-2007, Kohsuke Ohtani
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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. 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 THE AUTHOR 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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* cond.c - condition variable object
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*/
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#include <kernel.h> |
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#include <sched.h> |
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#include <event.h> |
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#include <kmem.h> |
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#include <task.h> |
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#include <sync.h> |
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/* forward declarations */
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static int cond_valid(cond_t); |
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static int cond_copyin(cond_t *, cond_t *); |
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/*
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* Create and initialize a condition variable (CV).
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*
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* If an initialized condition variable is reinitialized,
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* undefined behavior results.
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*/
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int
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cond_init(cond_t *cp) |
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{ |
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task_t self = curtask; |
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cond_t c; |
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if (self->nsyncs >= MAXSYNCS)
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return EAGAIN;
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if ((c = kmem_alloc(sizeof(struct cond))) == NULL) |
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return ENOMEM;
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event_init(&c->event, "condvar");
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c->owner = self; |
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if (copyout(&c, cp, sizeof(c))) { |
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kmem_free(c); |
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return EFAULT;
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} |
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sched_lock(); |
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list_insert(&self->conds, &c->task_link); |
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self->nsyncs++; |
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sched_unlock(); |
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return 0; |
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} |
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static void |
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cond_deallocate(cond_t c) |
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{ |
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c->owner->nsyncs--; |
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list_remove(&c->task_link); |
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kmem_free(c); |
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} |
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/*
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* Tear down a condition variable.
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*
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* If there are any blocked thread waiting for the specified
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* CV, it returns EBUSY.
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*/
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int
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cond_destroy(cond_t *cp) |
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{ |
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cond_t c; |
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sched_lock(); |
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if (cond_copyin(cp, &c)) {
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sched_unlock(); |
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return EINVAL;
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} |
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if (event_waiting(&c->event)) {
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sched_unlock(); |
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return EBUSY;
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} |
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cond_deallocate(c); |
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sched_unlock(); |
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return 0; |
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} |
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/*
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* Clean up for task termination.
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*/
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void
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cond_cleanup(task_t task) |
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{ |
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cond_t c; |
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while (!list_empty(&task->conds)) {
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c = list_entry(list_first(&task->conds), |
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struct cond, task_link);
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cond_deallocate(c); |
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} |
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} |
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/*
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* Wait on a condition.
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*
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* If the thread receives any exception while waiting CV, this
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* routine returns immediately with EINTR in order to invoke
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* exception handler. However, an application assumes this call
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* does NOT return with an error. So, the stub routine in a
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* system call library must call cond_wait() again if it gets
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* EINTR as error.
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*/
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int
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cond_wait(cond_t *cp, mutex_t *mp) |
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{ |
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cond_t c; |
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int error, rc;
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if (copyin(cp, &c, sizeof(cp))) |
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return EINVAL;
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sched_lock(); |
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if (c == COND_INITIALIZER) {
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if ((error = cond_init(cp)) != 0) { |
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sched_unlock(); |
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return error;
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} |
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copyin(cp, &c, sizeof(cp));
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} else {
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if (!cond_valid(c)) {
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sched_unlock(); |
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return EINVAL;
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} |
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} |
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/* unlock mutex */
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if ((error = mutex_unlock(mp)) != 0) { |
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sched_unlock(); |
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return error;
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} |
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/* and block */
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rc = sched_sleep(&c->event); |
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if (rc == SLP_INTR)
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error = EINTR; |
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sched_unlock(); |
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/* grab mutex before returning */
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if (error == 0) |
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error = mutex_lock(mp); |
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return error;
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} |
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/*
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* Unblock one thread that is blocked on the specified CV.
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* The thread which has highest priority will be unblocked.
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*/
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int
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cond_signal(cond_t *cp) |
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{ |
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cond_t c; |
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sched_lock(); |
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if (cond_copyin(cp, &c)) {
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sched_unlock(); |
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return EINVAL;
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} |
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sched_wakeone(&c->event); |
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sched_unlock(); |
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return 0; |
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} |
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/*
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* Unblock all threads that are blocked on the specified CV.
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*/
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int
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cond_broadcast(cond_t *cp) |
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{ |
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cond_t c; |
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sched_lock(); |
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if (cond_copyin(cp, &c)) {
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sched_unlock(); |
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return EINVAL;
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} |
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sched_wakeup(&c->event); |
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sched_unlock(); |
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return 0; |
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} |
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/*
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* Check if the specified cv is valid.
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*/
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static int |
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cond_valid(cond_t c) |
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{ |
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cond_t tmp; |
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list_t head, n; |
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head = &curtask->conds; |
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for (n = list_first(head); n != head; n = list_next(n)) {
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tmp = list_entry(n, struct cond, task_link);
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if (tmp == c)
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return 1; |
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} |
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return 0; |
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} |
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/*
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* cond_copyin - copy a condition variable from user space.
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* It also checks if the passed CV is valid.
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*/
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static int |
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cond_copyin(cond_t *ucp, cond_t *kcp) |
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{ |
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cond_t c; |
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if (copyin(ucp, &c, sizeof(ucp)) || !cond_valid(c)) |
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return EINVAL;
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*kcp = c; |
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return 0; |
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} |