sched/getpid.c

/************************************************************************
 * sched/getpid.c
 *
 *   Copyright (C) 2007, 2009, 2014 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
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 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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 ************************************************************************/

/************************************************************************
 * Included Files
 ************************************************************************/

#include <sys/types.h>
#include <unistd.h>
#include <sched.h>

#include "os_internal.h"

/************************************************************************
 * Pre-processor Definitions
 ************************************************************************/

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

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

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

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

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

/************************************************************************
 * Name: getpid
 *
 * Description:
 *   Get the task ID of the currently executing task.
 *
 ************************************************************************/

pid_t getpid(void)
{
  FAR struct tcb_s *rtcb;

  /* Get the the TCB at the head of the ready-to-run task list.  That
   * will be the currently executing task.  There is an exception to
   * this:  Verify early in the start-up sequence, the g_readytorun
   * list may be empty!  This case, of course, the start-up/IDLE thread
   * with pid == 0 must be running.
   */

  rtcb = (FAR struct tcb_s *)g_readytorun.head;
  if (rtcb)
    {
      /* Return the task ID from the TCB at the head of the ready-to-run
       * task list
       */

      return rtcb->pid;
    }

  /* We must have been called earlier in the start up sequence from the
   * start-up/IDLE thread before the g_readytorun list has been initialized.
   */

  return 0;
}