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- /****************************************************************************
- * sched/mqueue/mq_notify.c
- *
- * Copyright (C) 2007, 2009, 2011, 2013, 2015 Gregory Nutt. All rights reserved.
- * Author: Gregory Nutt <gnutt@nuttx.org>
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in
- * the documentation and/or other materials provided with the
- * distribution.
- * 3. Neither the name NuttX nor the names of its contributors may be
- * used to endorse or promote products derived from this software
- * without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
- * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
- * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
- * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
- * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
- * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
- * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- * POSSIBILITY OF SUCH DAMAGE.
- *
- ****************************************************************************/
- /****************************************************************************
- * Included Files
- ****************************************************************************/
- #include <nuttx/config.h>
- #include <mqueue.h>
- #include <sched.h>
- #include <string.h>
- #include <errno.h>
- #include <nuttx/sched.h>
- #include "sched/sched.h"
- #include "mqueue/mqueue.h"
- /****************************************************************************
- * Public Functions
- ****************************************************************************/
- /****************************************************************************
- * Name: mq_notify
- *
- * Description:
- * If "notification" is not NULL, this function connects the task with
- * the message queue such that the specified signal will be sent to the
- * task whenever the message changes from empty to non-empty. Only one
- * notification can be attached to a message queue.
- *
- * If "notification" is NULL, the attached notification is detached (if
- * it was held by the calling task) and the queue is available to attach
- * another notification.
- *
- * When the notification is sent to the registered process, its
- * registration will be removed. The message queue will then be
- * available for registration.
- *
- * Input Parameters:
- * mqdes - Message queue descriptor
- * notification - Real-time signal structure containing:
- * sigev_notify - Should be SIGEV_SIGNAL or SIGEV_THREAD
- * sigev_signo - The signo to use for the notification
- * sigev_value - Value associated with the signal
- *
- * Returned Value:
- * On success mq_notify() returns 0; on error, -1 is returned, with
- * errno set to indicate the error.
- *
- * EBADF The descriptor specified in mqdes is invalid.
- * EBUSY Another process has already registered to receive notification
- * for this message queue.
- * EINVAL sevp->sigev_notify is not one of the permitted values; or
- * sevp->sigev_notify is SIGEV_SIGNAL and sevp->sigev_signo is not a
- * valid signal number.
- * ENOMEM
- * Insufficient memory.
- *
- * Assumptions:
- *
- * POSIX Compatibility:
- * int mq_notify(mqd_t mqdes, const struct sigevent *notification);
- *
- * The notification will be sent to the registered task even if another
- * task is waiting for the message queue to become non-empty. This is
- * inconsistent with the POSIX specification which says, "If a process
- * has registered for notification of message a arrival at a message
- * queue and some process is blocked in [nx]mq_receive() waiting to receive
- * a message when a message arrives at the queue, the arriving message
- * message shall satisfy [nx]mq_receive()... The resulting behavior is as
- * if the message queue remains empty, and no notification shall be sent."
- *
- ****************************************************************************/
- int mq_notify(mqd_t mqdes, FAR const struct sigevent *notification)
- {
- FAR struct tcb_s *rtcb;
- FAR struct mqueue_inode_s *msgq;
- int errval;
- /* Was a valid message queue descriptor provided? */
- if (!mqdes)
- {
- /* No.. return EBADF */
- errval = EBADF;
- goto errout;
- }
- /* Get a pointer to the message queue */
- sched_lock();
- msgq = mqdes->msgq;
- /* Get the current process ID */
- rtcb = this_task();
- /* Is there already a notification attached */
- if (!msgq->ntmqdes)
- {
- /* No... Have we been asked to establish one? */
- if (notification)
- {
- /* Yes... Was a valid signal number supplied? */
- if (!GOOD_SIGNO(notification->sigev_signo))
- {
- /* No... Return EINVAL */
- errval = EINVAL;
- goto errout;
- }
- /* Yes... Assign it to the current task. */
- memcpy(&msgq->ntevent, notification,
- sizeof(struct sigevent));
- msgq->ntpid = rtcb->pid;
- msgq->ntmqdes = mqdes;
- }
- }
- /* Yes... a notification is attached. Does this task own it?
- * Is it trying to remove it?
- */
- else if ((msgq->ntpid != rtcb->pid) || (notification))
- {
- /* This thread does not own the notification OR it is
- * not trying to remove it. Return EBUSY.
- */
- errval = EBUSY;
- goto errout;
- }
- else
- {
- /* Yes, the notification belongs to this thread. Allow the
- * thread to detach the notification.
- */
- memset(&msgq->ntevent, 0, sizeof(struct sigevent));
- msgq->ntpid = INVALID_PROCESS_ID;
- msgq->ntmqdes = NULL;
- nxsig_cancel_notification(&msgq->ntwork);
- }
- sched_unlock();
- return OK;
- errout:
- set_errno(errval);
- sched_unlock();
- return ERROR;
- }
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