142 lines
4.4 KiB
C
142 lines
4.4 KiB
C
/****************************************************************************
|
|
* libc/misc/lib_filesem.c
|
|
*
|
|
* Copyright (C) 2007, 2009, 2011, 2017 Gregory Nutt. All rights reserved.
|
|
* Author: Gregory Nutt <gnutt@nuttx.org>
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
*
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* 2. Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in
|
|
* the documentation and/or other materials provided with the
|
|
* distribution.
|
|
* 3. Neither the name NuttX nor the names of its contributors may be
|
|
* used to endorse or promote products derived from this software
|
|
* without specific prior written permission.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
|
|
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
|
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
|
|
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
|
|
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
|
|
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
|
|
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
|
|
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
|
|
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
|
|
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
* POSSIBILITY OF SUCH DAMAGE.
|
|
*
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Included Files
|
|
****************************************************************************/
|
|
|
|
#include <nuttx/config.h>
|
|
|
|
#include <sys/types.h>
|
|
#include <unistd.h>
|
|
#include <semaphore.h>
|
|
#include <errno.h>
|
|
#include <assert.h>
|
|
|
|
#include <nuttx/semaphore.h>
|
|
#include <nuttx/fs/fs.h>
|
|
|
|
#include "libc.h"
|
|
|
|
#ifndef CONFIG_STDIO_DISABLE_BUFFERING
|
|
|
|
/****************************************************************************
|
|
* Public Functions
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* lib_sem_initialize
|
|
****************************************************************************/
|
|
|
|
void lib_sem_initialize(FAR struct file_struct *stream)
|
|
{
|
|
/* Initialize the LIB semaphore to one (to support one-at-a-time access
|
|
* to private data sets.
|
|
*/
|
|
|
|
(void)nxsem_init(&stream->fs_sem, 0, 1);
|
|
|
|
stream->fs_holder = -1;
|
|
stream->fs_counts = 0;
|
|
}
|
|
|
|
/****************************************************************************
|
|
* lib_take_semaphore
|
|
****************************************************************************/
|
|
|
|
void lib_take_semaphore(FAR struct file_struct *stream)
|
|
{
|
|
pid_t my_pid = getpid();
|
|
int ret;
|
|
|
|
/* Do I already have the semaphore? */
|
|
|
|
if (stream->fs_holder == my_pid)
|
|
{
|
|
/* Yes, just increment the number of references that I have */
|
|
|
|
stream->fs_counts++;
|
|
}
|
|
else
|
|
{
|
|
/* Take the semaphore (perhaps waiting) */
|
|
|
|
while ((ret = _SEM_WAIT(&stream->fs_sem)) < 0)
|
|
{
|
|
/* The only case that an error should occr here is if the wait
|
|
* was awakened by a signal.
|
|
*/
|
|
|
|
DEBUGASSERT(_SEM_ERRNO(ret) == EINTR);
|
|
UNUSED(ret);
|
|
}
|
|
|
|
/* We have it. Claim the stak and return */
|
|
|
|
stream->fs_holder = my_pid;
|
|
stream->fs_counts = 1;
|
|
}
|
|
}
|
|
|
|
/****************************************************************************
|
|
* lib_give_semaphore
|
|
****************************************************************************/
|
|
|
|
void lib_give_semaphore(FAR struct file_struct *stream)
|
|
{
|
|
/* I better be holding at least one reference to the semaphore */
|
|
|
|
DEBUGASSERT(stream->fs_holder == getpid());
|
|
|
|
/* Do I hold multiple references to the semphore */
|
|
|
|
if (stream->fs_counts > 1)
|
|
{
|
|
/* Yes, just release one count and return */
|
|
|
|
stream->fs_counts--;
|
|
}
|
|
else
|
|
{
|
|
/* Nope, this is the last reference I have */
|
|
|
|
stream->fs_holder = -1;
|
|
stream->fs_counts = 0;
|
|
DEBUGVERIFY(_SEM_POST(&stream->fs_sem));
|
|
}
|
|
}
|
|
|
|
#endif /* CONFIG_STDIO_DISABLE_BUFFERING */
|