99 lines
2.9 KiB
C
99 lines
2.9 KiB
C
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/****************************************************************************
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* libs/libc/semaphore/sem_wait.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/cancelpt.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_wait
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*
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* Description:
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* This function attempts to lock the semaphore referenced by 'sem'. If
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* the semaphore value is (<=) zero, then the calling task will not return
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* until it successfully acquires the lock.
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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 returns
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* zero (OK) if successful. Otherwise, -1 (ERROR) is returned and
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* the errno value is set appropriately. Possible errno values include:
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*
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* - EINVAL: Invalid attempt to get the semaphore
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* - EINTR: The wait was interrupted by the receipt of a signal.
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*
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****************************************************************************/
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int sem_wait(FAR sem_t *sem)
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{
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int errcode;
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int ret;
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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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/* sem_wait() is a cancellation point */
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if (enter_cancellation_point())
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{
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#ifdef CONFIG_CANCELLATION_POINTS
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/* If there is a pending cancellation, then do not perform
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* the wait. Exit now with ECANCELED.
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*/
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errcode = ECANCELED;
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goto errout_with_cancelpt;
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#endif
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}
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/* Let nxsem_wait() do the real work */
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ret = nxsem_wait(sem);
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if (ret < 0)
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{
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errcode = -ret;
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goto errout_with_cancelpt;
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}
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leave_cancellation_point();
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return OK;
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errout_with_cancelpt:
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set_errno(errcode);
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leave_cancellation_point();
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return ERROR;
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}
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