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/**
* @file
*
* @ingroup POSIXAPI
*
* @brief Function Creates New POSIX semaphore or Opens an existing Semaphore
*/
/*
* COPYRIGHT (c) 1989-2007.
* On-Line Applications Research Corporation (OAR).
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.org/license/LICENSE.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <rtems/posix/semaphoreimpl.h>
#include <rtems/score/wkspace.h>
#include <rtems/sysinit.h>
#include <stdarg.h>
#include <fcntl.h>
#include <limits.h>
static sem_t *_POSIX_Semaphore_Create_support(
const char *name_arg,
size_t name_len,
unsigned int value
)
{
POSIX_Semaphore_Control *the_semaphore;
char *name;
if ( value > SEM_VALUE_MAX ) {
rtems_set_errno_and_return_value( EINVAL, SEM_FAILED );
}
/*
* Make a copy of the user's string for name just in case it was
* dynamically constructed.
*/
name = _Workspace_String_duplicate( name_arg, name_len );
if ( name == NULL ) {
rtems_set_errno_and_return_value( ENOMEM, SEM_FAILED );
}
the_semaphore = _POSIX_Semaphore_Allocate_unprotected();
if ( the_semaphore == NULL ) {
_Workspace_Free( name );
rtems_set_errno_and_return_value( ENOSPC, SEM_FAILED );
}
the_semaphore->open_count = 1;
the_semaphore->linked = true;
/*
* POSIX does not appear to specify what the discipline for
* blocking tasks on this semaphore should be. It could somehow
* be derived from the current scheduling policy. One
* thing is certain, no matter what we decide, it won't be
* the same as all other POSIX implementations. :)
*/
_POSIX_Semaphore_Initialize( &the_semaphore->Semaphore, name, value );
/*
* Make the semaphore available for use.
*/
_Objects_Open_string(
&_POSIX_Semaphore_Information,
&the_semaphore->Object,
name
);
return &the_semaphore->Semaphore;
}
/*
* sem_open
*
* Opens a named semaphore. Used in conjunction with the sem_close
* and sem_unlink commands.
*
* 11.2.3 Initialize/Open a Named Semaphore, P1003.1b-1993, p.221
*
* NOTE: When oflag is O_CREAT, then optional third and fourth
* parameters must be present.
*/
sem_t *sem_open(
const char *name,
int oflag,
...
/* mode_t mode, */
/* unsigned int value */
)
{
/*
* mode is set but never used. GCC gives a warning for this
* and we need to tell GCC not to complain. But we have to
* have it because we have to work through the variable
* arguments to get to attr.
*/
mode_t mode RTEMS_UNUSED;
va_list arg;
unsigned int value = 0;
POSIX_Semaphore_Control *the_semaphore;
size_t name_len;
Objects_Get_by_name_error error;
sem_t *sem;
if ( oflag & O_CREAT ) {
va_start(arg, oflag);
mode = va_arg( arg, mode_t );
value = va_arg( arg, unsigned int );
va_end(arg);
}
_Objects_Allocator_lock();
the_semaphore = _POSIX_Semaphore_Get_by_name( name, &name_len, &error );
/*
* If the name to id translation worked, then the semaphore exists
* and we can just return a pointer to the id. Otherwise we may
* need to check to see if this is a "semaphore does not exist"
* or some other miscellaneous error on the name.
*/
if ( the_semaphore == NULL ) {
/*
* Unless provided a valid name that did not already exist
* and we are willing to create then it is an error.
*/
if ( !( error == OBJECTS_GET_BY_NAME_NO_OBJECT && (oflag & O_CREAT) ) ) {
_Objects_Allocator_unlock();
rtems_set_errno_and_return_value(
_POSIX_Get_by_name_error( error ),
SEM_FAILED
);
}
} else {
/*
* Check for existence with creation.
*/
if ( (oflag & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL) ) {
_Objects_Allocator_unlock();
rtems_set_errno_and_return_value( EEXIST, SEM_FAILED );
}
the_semaphore->open_count += 1;
_Objects_Allocator_unlock();
return &the_semaphore->Semaphore;
}
/*
* At this point, the semaphore does not exist and everything has been
* checked. We should go ahead and create a semaphore.
*/
sem = _POSIX_Semaphore_Create_support(
name,
name_len,
value
);
_Objects_Allocator_unlock();
return sem;
}
static void _POSIX_Semaphore_Manager_initialization( void )
{
_Objects_Initialize_information( &_POSIX_Semaphore_Information );
}
RTEMS_SYSINIT_ITEM(
_POSIX_Semaphore_Manager_initialization,
RTEMS_SYSINIT_POSIX_SEMAPHORE,
RTEMS_SYSINIT_ORDER_MIDDLE
);
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