/************************************************************
* mq_notify.c
*
* Copyright (C) 2007 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
*
* 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 Gregory Nutt 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 <sys/types.h> /* uint32, etc. */
#include <signal.h>
#include <mqueue.h>
#include <sched.h>
#include "os_internal.h"
#include "mq_internal.h"
/************************************************************
* Definitions
************************************************************/
/************************************************************
* Private Type Declarations
************************************************************/
/************************************************************
* Global Variables
************************************************************/
/************************************************************
* Private Variables
************************************************************/
/************************************************************
* Private Functions
************************************************************/
/************************************************************
* Public Functions
************************************************************/
/************************************************************
* Function: 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. One 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.
*
* Parameters:
* mqdes - Message queue descriptor
* notification - Real-time signal structure containing:
* sigev_notify - Should be SIGEV_SIGNAL (but actually ignored)
* sigev_signo - The signo to use for the notification
* sigev_value - Value associated with the signal
*
* Return Value:
* None
*
* 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 mq_receive() waiting to receive
* a message when a message arrives at the queue, the arriving message
* message shall satisfy 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, const struct sigevent *notification)
{
_TCB *rtcb;
msgq_t *msgq;
int ret = ERROR;
if (mqdes)
{
sched_lock();
/* Get a pointer to the message queue */
msgq = mqdes->msgq;
/* Get the current process ID */
rtcb = (_TCB*)g_readytorun.head;
/* Is there already a notification attached */
if (!msgq->ntmqdes)
{
/* No... Have we been asked to establish one? Make
* sure a good signal number has been provided
*/
if (notification && GOOD_SIGNO(notification->sigev_signo))
{
/* Yes... Assign it to the current task. */
msgq->ntvalue.sival_ptr = notification->sigev_value.sival_ptr;
msgq->ntsigno = notification->sigev_signo;
msgq->ntpid = rtcb->pid;
msgq->ntmqdes = mqdes;
ret = OK;
}
}
/* Yes... a notification is attached. Does this task own it?
* Is it trying to remove it?
*/
else if ((msgq->ntpid == rtcb->pid) && (!notification))
{
/* Yes... Detach the notification */
msgq->ntpid = INVALID_PROCESS_ID;
msgq->ntsigno = 0;
msgq->ntvalue.sival_ptr = NULL;
msgq->ntmqdes = NULL;
ret = OK;
}
sched_unlock();
}
return ret;
}
