85 lines
2.8 KiB
C
85 lines
2.8 KiB
C
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/****************************************************************************
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* libs/libc/semaphore/sem_post.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 <errno.h>
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#include <nuttx/semaphore.h>
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: sem_post
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*
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* Description:
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* When a task has finished with a semaphore, it will call sem_post().
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* This function unlocks the semaphore referenced by sem by performing the
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* semaphore unlock operation on that semaphore.
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*
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* If the semaphore value resulting from this operation is positive, then
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* no tasks were blocked waiting for the semaphore to become unlocked; the
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* semaphore is simply incremented.
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*
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* If the value of the semaphore resulting from this operation is zero,
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* then one of the tasks blocked waiting for the semaphore shall be
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* allowed to return successfully from its call to nxsem_wait().
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*
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* Input Parameters:
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* sem - Semaphore descriptor
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*
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* Returned Value:
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* This function is a standard, POSIX application interface. It will
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* return zero (OK) if successful. Otherwise, -1 (ERROR) is returned and
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* the errno value is set appropriately.
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*
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* Assumptions:
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* This function may be called from an interrupt handler.
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*
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****************************************************************************/
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int sem_post(FAR sem_t *sem)
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{
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int ret;
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/* Make sure we were supplied with a valid semaphore. */
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if (sem == NULL)
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{
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set_errno(EINVAL);
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return ERROR;
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}
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ret = nxsem_post(sem);
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if (ret < 0)
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{
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set_errno(-ret);
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ret = ERROR;
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}
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return ret;
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}
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