b7c451c5a4
Gregory Nutt has submitted the SGA and we can migrate the licenses to Apache. Signed-off-by: Alin Jerpelea <alin.jerpelea@sony.com>
127 lines
3.6 KiB
C
127 lines
3.6 KiB
C
/****************************************************************************
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* libs/libc/misc/lib_filesem.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 <sys/types.h>
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#include <unistd.h>
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#include <errno.h>
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#include <assert.h>
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#include <nuttx/semaphore.h>
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#include <nuttx/fs/fs.h>
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#include "libc.h"
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#ifndef CONFIG_STDIO_DISABLE_BUFFERING
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* lib_sem_initialize
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****************************************************************************/
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void lib_sem_initialize(FAR struct file_struct *stream)
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{
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/* Initialize the LIB semaphore to one (to support one-at-a-time access
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* to private data sets.
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*/
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_SEM_INIT(&stream->fs_sem, 0, 1);
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stream->fs_holder = -1;
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stream->fs_counts = 0;
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}
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/****************************************************************************
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* lib_take_semaphore
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****************************************************************************/
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void lib_take_semaphore(FAR struct file_struct *stream)
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{
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pid_t my_pid = getpid();
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int ret;
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/* Do I already have the semaphore? */
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if (stream->fs_holder == my_pid)
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{
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/* Yes, just increment the number of references that I have */
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stream->fs_counts++;
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}
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else
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{
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/* Take the semaphore (perhaps waiting) */
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while ((ret = _SEM_WAIT(&stream->fs_sem)) < 0)
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{
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/* The only case that an error should occr here is if the wait
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* was awakened by a signal.
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*/
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DEBUGASSERT(_SEM_ERRNO(ret) == EINTR ||
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_SEM_ERRNO(ret) == ECANCELED);
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UNUSED(ret);
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}
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/* We have it. Claim the stak and return */
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stream->fs_holder = my_pid;
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stream->fs_counts = 1;
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}
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}
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/****************************************************************************
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* lib_give_semaphore
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****************************************************************************/
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void lib_give_semaphore(FAR struct file_struct *stream)
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{
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/* I better be holding at least one reference to the semaphore */
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DEBUGASSERT(stream->fs_holder == getpid());
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/* Do I hold multiple references to the semphore */
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if (stream->fs_counts > 1)
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{
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/* Yes, just release one count and return */
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stream->fs_counts--;
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}
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else
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{
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/* Nope, this is the last reference I have */
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stream->fs_holder = -1;
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stream->fs_counts = 0;
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DEBUGVERIFY(_SEM_POST(&stream->fs_sem));
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}
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}
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#endif /* CONFIG_STDIO_DISABLE_BUFFERING */
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