nuttx/sched/mqueue/mq_notify.c

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/****************************************************************************
* sched/mqueue/mq_notify.c
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <mqueue.h>
#include <sched.h>
#include <string.h>
#include <errno.h>
#include <nuttx/irq.h>
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#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.
*
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* EBADF The descriptor specified in mqdes is invalid.
* EBUSY Another process has already registered to receive notification
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* 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
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* 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)
{
#ifndef CONFIG_DISABLE_MQUEUE_NOTIFICATION
FAR struct mqueue_inode_s *msgq;
FAR struct inode *inode;
FAR struct file *filep;
FAR struct tcb_s *rtcb;
irqstate_t flags;
int errval;
errval = fs_getfilep(mqdes, &filep);
if (errval < 0)
{
errval = -errval;
goto errout_without_lock;
}
inode = filep->f_inode;
/* Was a valid message queue descriptor provided? */
if (!inode->i_private)
{
/* No.. return EBADF */
errval = EBADF;
goto errout_with_filep;
}
/* Get a pointer to the message queue */
flags = enter_critical_section();
/* Get the current process ID */
rtcb = this_task();
/* Is there already a notification attached */
msgq = inode->i_private;
if (msgq->ntpid == INVALID_PROCESS_ID)
{
/* 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;
}
}
/* Yes... a notification is attached. Does this task own it?
* Is it trying to remove it?
*/
else if ((msgq->ntpid != rtcb->pid) || (notification != NULL))
{
/* 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;
nxsig_cancel_notification(&msgq->ntwork);
}
leave_critical_section(flags);
fs_putfilep(filep);
return OK;
errout:
leave_critical_section(flags);
errout_with_filep:
fs_putfilep(filep);
errout_without_lock:
set_errno(errval);
return ERROR;
#else
set_errno(ENOSYS);
return ERROR;
#endif
}