190 lines
5.8 KiB
C
190 lines
5.8 KiB
C
/****************************************************************************
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* sched/mqueue/mq_notify.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <mqueue.h>
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#include <sched.h>
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#include <string.h>
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#include <errno.h>
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#include <nuttx/sched.h>
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#include "sched/sched.h"
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#include "mqueue/mqueue.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: mq_notify
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*
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* Description:
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* If "notification" is not NULL, this function connects the task with
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* the message queue such that the specified signal will be sent to the
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* task whenever the message changes from empty to non-empty. Only one
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* notification can be attached to a message queue.
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*
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* If "notification" is NULL, the attached notification is detached (if
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* it was held by the calling task) and the queue is available to attach
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* another notification.
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*
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* When the notification is sent to the registered process, its
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* registration will be removed. The message queue will then be
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* available for registration.
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*
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* Input Parameters:
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* mqdes - Message queue descriptor
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* notification - Real-time signal structure containing:
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* sigev_notify - Should be SIGEV_SIGNAL or SIGEV_THREAD
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* sigev_signo - The signo to use for the notification
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* sigev_value - Value associated with the signal
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*
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* Returned Value:
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* On success mq_notify() returns 0; on error, -1 is returned, with
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* errno set to indicate the error.
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*
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* EBADF The descriptor specified in mqdes is invalid.
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* EBUSY Another process has already registered to receive notification
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* for this message queue.
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* EINVAL sevp->sigev_notify is not one of the permitted values; or
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* sevp->sigev_notify is SIGEV_SIGNAL and sevp->sigev_signo is not a
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* valid signal number.
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* ENOMEM
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* Insufficient memory.
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*
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* Assumptions:
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*
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* POSIX Compatibility:
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* int mq_notify(mqd_t mqdes, const struct sigevent *notification);
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*
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* The notification will be sent to the registered task even if another
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* task is waiting for the message queue to become non-empty. This is
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* inconsistent with the POSIX specification which says, "If a process
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* has registered for notification of message a arrival at a message
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* queue and some process is blocked in [nx]mq_receive() waiting to receive
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* a message when a message arrives at the queue, the arriving message
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* message shall satisfy [nx]mq_receive()... The resulting behavior is as
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* if the message queue remains empty, and no notification shall be sent."
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*
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****************************************************************************/
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int mq_notify(mqd_t mqdes, FAR const struct sigevent *notification)
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{
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FAR struct mqueue_inode_s *msgq;
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FAR struct inode *inode;
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FAR struct file *filep;
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FAR struct tcb_s *rtcb;
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int errval;
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errval = fs_getfilep(mqdes, &filep);
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if (errval < 0)
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{
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goto errout_without_lock;
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}
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inode = filep->f_inode;
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/* Was a valid message queue descriptor provided? */
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if (!inode || !inode->i_private)
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{
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/* No.. return EBADF */
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errval = EBADF;
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goto errout_without_lock;
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}
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/* Get a pointer to the message queue */
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sched_lock();
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/* Get the current process ID */
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rtcb = this_task();
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/* Is there already a notification attached */
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msgq = inode->i_private;
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if (msgq->ntpid == INVALID_PROCESS_ID)
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{
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/* No... Have we been asked to establish one? */
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if (notification)
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{
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/* Yes... Was a valid signal number supplied? */
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if (!GOOD_SIGNO(notification->sigev_signo))
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{
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/* No... Return EINVAL */
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errval = EINVAL;
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goto errout;
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}
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/* Yes... Assign it to the current task. */
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memcpy(&msgq->ntevent, notification,
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sizeof(struct sigevent));
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msgq->ntpid = rtcb->pid;
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}
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}
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/* Yes... a notification is attached. Does this task own it?
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* Is it trying to remove it?
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*/
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else if ((msgq->ntpid != rtcb->pid) || (notification))
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{
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/* This thread does not own the notification OR it is
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* not trying to remove it. Return EBUSY.
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*/
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errval = EBUSY;
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goto errout;
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}
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else
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{
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/* Yes, the notification belongs to this thread. Allow the
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* thread to detach the notification.
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*/
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memset(&msgq->ntevent, 0, sizeof(struct sigevent));
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msgq->ntpid = INVALID_PROCESS_ID;
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nxsig_cancel_notification(&msgq->ntwork);
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}
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sched_unlock();
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return OK;
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errout:
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sched_unlock();
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errout_without_lock:
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set_errno(errval);
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return ERROR;
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}
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