116 lines
4.3 KiB
C
116 lines
4.3 KiB
C
/****************************************************************************
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* sched/task/task_getpid.c
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*
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* Copyright (C) 2007, 2009, 2014, 2018 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <sys/types.h>
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#include <unistd.h>
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#include <sched.h>
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#include <errno.h>
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#include "sched/sched.h"
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#include "task/task.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: getpid
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*
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* Description:
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* Get the task ID of the currently executing task.
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*
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* Input parameters:
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* None
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*
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* Returned Value:
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* Normally when called from user applications, getpid() will return the
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* task ID of the currently executing task, that is, the task at the head
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* of the ready-to-run list. There is no specification for any errors
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* returned from getpid().
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*
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* getpid(), however, may be called from within the OS in some cases.
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* There are certain situations during context switching when the OS data
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* structures are in flux and where the current task at the head of the
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* ready-to-run task list is not actually running. In that case,
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* getpid() will return the error: -ESRCH
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*
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****************************************************************************/
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pid_t getpid(void)
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{
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FAR struct tcb_s *rtcb;
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/* Get the TCB at the head of the ready-to-run task list. That
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* will usually be the currently executing task. There is are two
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* exceptions to this:
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*
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* 1. Early in the start-up sequence, the ready-to-run list may be
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* empty! In this case, of course, the CPU0 start-up/IDLE thread with
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* pid == 0 must be running, and
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* 2. As described above, during certain context-switching conditions the
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* task at the head of the ready-to-run list may not actually be
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* running.
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*/
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rtcb = this_task();
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if (rtcb != NULL)
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{
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/* Check if the task is actually running */
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if (rtcb->task_state == TSTATE_TASK_RUNNING)
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{
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/* Yes.. Return the task ID from the TCB at the head of the
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* ready-to-run task list
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*/
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return rtcb->pid;
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}
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/* No.. return -ESRCH to indicate this condition */
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return (pid_t)-ESRCH;
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}
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/* We must have been called earlier in the start up sequence from the
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* start-up/IDLE thread before the ready-to-run list has been initialized.
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*/
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return (pid_t)0;
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}
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