/************************************************************************
* sched/mq_notify.c
*
* Copyright (C) 2007, 2009, 2011 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 <signal.h>
#include <mqueue.h>
#include <sched.h>
#include <errno.h>
#include "os_internal.h"
#include "mq_internal.h"
/************************************************************************
* Definitions
************************************************************************/
/************************************************************************
* Private Type Declarations
************************************************************************/
/************************************************************************
* Global Variables
************************************************************************/
/************************************************************************
* Private Variables
************************************************************************/
/************************************************************************
* Private Functions
************************************************************************/
/************************************************************************
* 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.
*
* 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:
* 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 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 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 = (_TCB*)g_readytorun.head;
/* 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. */
msgq->ntvalue.sival_ptr = notification->sigev_value.sival_ptr;
msgq->ntsigno = notification->sigev_signo;
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.
*/
msgq->ntpid = INVALID_PROCESS_ID;
msgq->ntsigno = 0;
msgq->ntvalue.sival_ptr = NULL;
msgq->ntmqdes = NULL;
}
sched_unlock();
return OK;
errout:
set_errno(errval);
sched_unlock();
return ERROR;
}
