px4-firmware/nuttx/sched/sched_getscheduler.c

/************************************************************************
 * sched/sched_getscheduler.c
 *
 *   Copyright (C) 2007, 2009 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 <sched.h>
#include <errno.h>
#include <nuttx/arch.h>
#include "os_internal.h"

/************************************************************************
 * Definitions
 ************************************************************************/

/************************************************************************
 * Private Type Declarations
 ************************************************************************/

/************************************************************************
 * Global Variables
 ************************************************************************/

/************************************************************************
 * Private Variables
 ************************************************************************/

/************************************************************************
 * Private Function Prototypes
 ************************************************************************/

/************************************************************************
 * Private Functions
 ************************************************************************/

/************************************************************************
 * Public Functions
 ************************************************************************/

/************************************************************************
 * Name: sched_getscheduler
 *
 * Description:
 *   sched_getscheduler() returns the scheduling policy
 *   currently applied to the process identified by pid. If
 *   pid equals zero, the policy of the calling process will
 *   be retrieved.
 *
 * Inputs:
 *   pid - the task ID of the task to query.  If pid is
 *     zero, the calling task is queried.
 *
 * Return Value:
 *    On success, sched_getscheduler() returns the policy for
 *    the task (either SCHED_FIFO or SCHED_RR).  On error,
 *    ERROR (-1) is returned, and errno is set appropriately:
 *
 *    ESRCH  The task whose ID is pid could not be found.
 *
 * Assumptions:
 *
 ************************************************************************/

int sched_getscheduler(pid_t pid)
{
  _TCB *tcb;

  /* Verify that the pid corresponds to a real task */

  if (!pid)
    {
      tcb = (_TCB*)g_readytorun.head;
    }
  else
    {
      tcb = sched_gettcb(pid);
    }

  if (!tcb)
    {
      *get_errno_ptr() = ESRCH;
      return ERROR;
    }
#if CONFIG_RR_INTERVAL > 0
  else if ((tcb->flags & TCB_FLAG_ROUND_ROBIN) != 0)
    {
      return SCHED_RR;
    }
#endif
  else
    {
      return SCHED_FIFO;
    }
}