forked from Archive/PX4-Autopilot
143 lines
4.3 KiB
C
143 lines
4.3 KiB
C
/*****************************************************************************
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* sched/task_reparent.c
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*
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* Copyright (C) 2013 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 <nuttx/config.h>
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#include <errno.h>
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#include "os_internal.h"
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#ifdef CONFIG_SCHED_HAVE_PARENT
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/*****************************************************************************
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* Private Functions
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*****************************************************************************/
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/*****************************************************************************
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* Public Functions
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*****************************************************************************/
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/*****************************************************************************
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* Name: task_reparent
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*
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* Description:
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* Change the parent of a task.
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*
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* Parameters:
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* ppid - PID of the new parent task (0 for grandparent, i.e. the parent
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* of the current parent task)
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* chpid - PID of the child to be reparented.
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*
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* Return Value:
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* 0 (OK) on success; A negated errno value on failure.
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*
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*****************************************************************************/
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int task_reparent(pid_t ppid, pid_t chpid)
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{
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_TCB *ptcb;
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_TCB *chtcb;
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_TCB *otcb;
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pid_t opid;
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irqstate_t flags;
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int ret;
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/* Disable interrupts so that nothing can change in the relatinoship of
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* the three task: Child, current parent, and new parent.
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*/
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flags = irqsave();
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/* Get the child tasks TCB (chtcb) */
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chtcb = sched_gettcb(chpid);
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if (!chtcb)
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{
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ret = -ECHILD;
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goto errout_with_ints;
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}
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/* Get the PID of the child task's parent (opid) */
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opid = chtcb->parent;
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/* Get the TCB of the child task's parent (otcb) */
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otcb = sched_gettcb(opid);
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if (!otcb)
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{
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ret = -ESRCH;
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goto errout_with_ints;
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}
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/* If new parent task's PID (ppid) is zero, then new parent is the
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* grandparent will be the new parent, i.e., the parent of the current
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* parent task.
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*/
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if (ppid == 0)
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{
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ppid = otcb->parent;
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}
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/* Get the new parent task's TCB (ptcb) */
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ptcb = sched_gettcb(ppid);
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if (!ptcb)
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{
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ret = -ESRCH;
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goto errout_with_ints;
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}
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/* Then reparent the child */
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DEBUGASSERT(otcb->nchildren > 0);
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chtcb->parent = ppid; /* The task specified by ppid is the new parent */
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otcb->nchildren--; /* The orignal parent now has one few children */
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ptcb->nchildren++; /* The new parent has one additional child */
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ret = OK;
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errout_with_ints:
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irqrestore(flags);
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return ret;
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}
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#endif /* CONFIG_SCHED_HAVE_PARENT */
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