207 lines
7.6 KiB
C
207 lines
7.6 KiB
C
/****************************************************************************
|
|
* sched/sem_open.c
|
|
*
|
|
* Copyright (C) 2007, 2008 Gregory Nutt. All rights reserved.
|
|
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
|
|
*
|
|
* 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 <stdbool.h>
|
|
#include <stdarg.h>
|
|
#include <limits.h>
|
|
#include <fcntl.h>
|
|
#include <string.h>
|
|
#include <semaphore.h>
|
|
#include <errno.h>
|
|
#include <nuttx/kmalloc.h>
|
|
#include "sem_internal.h"
|
|
|
|
/****************************************************************************
|
|
* Pre-processor Definitions
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Private Type Declarations
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Global Variables
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Private Variables
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Private Functions
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Public Functions
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Function: sem_open
|
|
*
|
|
* Description:
|
|
* This function establishes a connection between named semaphores and a
|
|
* task. Following a call to sem_open() with the semaphore name, the task
|
|
* may reference the semaphore associated with name using the address
|
|
* returned by this call. The semaphore may be used in subsequent calls
|
|
* to sem_wait(), sem_trywait(), and sem_post(). The semaphore remains
|
|
* usable until the semaphore is closed by a successful call to sem_close().
|
|
*
|
|
* If a task makes multiple calls to sem_open() with the same name, then
|
|
* the same semaphore address is returned (provided there have been no
|
|
* calls to sem_unlink()).
|
|
*
|
|
* Parameters:
|
|
* name - Semaphore name
|
|
* oflag - Semaphore creation options. This may either or both of the
|
|
* following bit settings.
|
|
* oflag = 0: Connect to the semaphore only if it already exists.
|
|
* oflag = O_CREAT: Connect to the semaphore if it exists, otherwise
|
|
* create the semaphore.
|
|
* oflag = O_CREAT|O_EXCL: Create a new semaphore
|
|
* unless one of this name already exists.
|
|
* Optional parameters. When the O_CREAT flag is specified, two optional
|
|
* parameters are expected:
|
|
* 1. mode_t mode (ignored), and
|
|
* 2. unsigned int value. This initial value of the semaphore. Valid
|
|
* initial values of the semaphore must be less than or equal to
|
|
* SEM_VALUE_MAX.
|
|
*
|
|
* Return Value:
|
|
* A pointer to sem_t or -1 (ERROR) if unsuccessful.
|
|
*
|
|
* Assumptions:
|
|
*
|
|
****************************************************************************/
|
|
|
|
FAR sem_t *sem_open (FAR const char *name, int oflag, ...)
|
|
{
|
|
int namelen;
|
|
FAR nsem_t *psem;
|
|
FAR sem_t *sem = (FAR sem_t*)ERROR;
|
|
va_list arg; /* Points to each un-named argument */
|
|
mode_t mode; /* Creation mode parameter (ignored) */
|
|
unsigned int value; /* Semaphore value parameter */
|
|
|
|
/* Make sure that a non-NULL name is supplied */
|
|
|
|
if (name)
|
|
{
|
|
/* The POSIX specification requires that the "check for the
|
|
* existence of a semaphore and the creation of the semaphore
|
|
* if it does not exist shall be atomic with respect to other
|
|
* processes executing sem_open()..." A simple sched_lock()
|
|
* should be sufficient to meet this requirement.
|
|
*/
|
|
|
|
sched_lock();
|
|
namelen = strlen(name);
|
|
if (namelen > 0)
|
|
{
|
|
/* See if the semaphore already exists */
|
|
|
|
psem = sem_findnamed(name);
|
|
if (psem)
|
|
{
|
|
/* It does. Check if the caller wanted to created
|
|
* a new semahore with this name.
|
|
*/
|
|
|
|
if (!(oflag & O_CREAT) || !(oflag & O_EXCL))
|
|
{
|
|
/* Allow a new connection to the semaphore */
|
|
|
|
psem->nconnect++;
|
|
sem = &psem->sem;
|
|
}
|
|
}
|
|
|
|
/* It doesn't exist. Should we create one? */
|
|
|
|
else if ((oflag & O_CREAT) != 0)
|
|
{
|
|
/* Set up to get the optional arguments needed to create
|
|
* a message queue.
|
|
*/
|
|
|
|
va_start(arg, oflag);
|
|
mode = va_arg(arg, mode_t);
|
|
value = va_arg(arg, unsigned int);
|
|
|
|
/* Verify that a legal initial value was selected. */
|
|
|
|
if (value <= SEM_VALUE_MAX)
|
|
{
|
|
/* Allocate memory for the new semaphore */
|
|
|
|
psem = (FAR nsem_t*)kmalloc((sizeof(nsem_t) + namelen + 1));
|
|
if (psem)
|
|
{
|
|
/* Initialize the named semaphore */
|
|
|
|
sem = &psem->sem;
|
|
sem_init(sem, 0, value);
|
|
|
|
psem->nconnect = 1;
|
|
psem->unlinked = false;
|
|
psem->name = (FAR char*)psem + sizeof(nsem_t);
|
|
strcpy(psem->name, name);
|
|
|
|
/* Add the new semaphore to the list of named
|
|
* semaphores
|
|
*/
|
|
|
|
dq_addfirst((FAR dq_entry_t*)psem, &g_nsems);
|
|
}
|
|
|
|
/* Clean-up variable argument stuff */
|
|
|
|
va_end(arg);
|
|
}
|
|
}
|
|
}
|
|
sched_unlock();
|
|
}
|
|
|
|
return sem;
|
|
}
|
|
|