nuttx/libs/libc/pthread/pthread_once.c

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/****************************************************************************
* libs/libc/pthread/pthread_once.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <stdbool.h>
#include <pthread.h>
#include <sched.h>
#include <errno.h>
#include <debug.h>
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: pthread_once
*
* Description:
* The first call to pthread_once() by any thread with a given
* once_control, will call the init_routine with no arguments. Subsequent
* calls to pthread_once() with the same once_control will have no effect.
* On return from pthread_once(), init_routine will have completed.
*
* Input Parameters:
* once_control - Determines if init_routine should be called.
* once_control should be declared and initializeed as follows:
*
* pthread_once_t once_control = PTHREAD_ONCE_INIT;
*
* PTHREAD_ONCE_INIT is defined in pthread.h
* init_routine - The initialization routine that will be called once.
*
* Returned Value:
* 0 (OK) on success or EINVAL if either once_control or init_routine are
* invalid
*
* Assumptions:
*
****************************************************************************/
int pthread_once(FAR pthread_once_t *once_control,
CODE void (*init_routine)(void))
{
/* Sanity checks */
if (once_control && init_routine)
{
/* Prohibit pre-emption while we test and set the once_control */
sched_lock();
if (!*once_control)
{
*once_control = true;
/* Call the init_routine with pre-emption enabled. */
sched_unlock();
init_routine();
return OK;
}
/* The init_routine has already been called. Restore pre-emption and return */
sched_unlock();
return OK;
}
/* One of the two arguments is NULL */
return EINVAL;
}