text: /****************************************************************************
   * sched/task/task_reparent.c
   *
   *   Copyright (C) 2013, 2016 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
   * 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 <errno.h>
  
  #include <nuttx/irq.h>
  
  #include "sched/sched.h"
  #include "group/group.h"
  #include "task/task.h"
  
  #ifdef CONFIG_SCHED_HAVE_PARENT
  
  /****************************************************************************
   * Public Functions
   ****************************************************************************/
  
  /****************************************************************************
   * Name: task_reparent
   *
   * Description:
   *   Change the parent of a task.
   *
   * Parameters:
   *   ppid - PID of the new parent task (0 for grandparent, i.e. the parent
   *     of the current parent task)
   *   chpid  - PID of the child to be reparented.
   *
   * Return Value:
   *   0 (OK) on success; A negated errno value on failure.
   *
   ****************************************************************************/
  
  #ifdef HAVE_GROUP_MEMBERS
  int task_reparent(pid_t ppid, pid_t chpid)
  {
  #ifdef CONFIG_SCHED_CHILD_STATUS
    FAR struct child_status_s *child;
  #endif
    FAR struct task_group_s *chgrp;
    FAR struct task_group_s *ogrp;
    FAR struct task_group_s *pgrp;
    struct tcb_s *tcb;
    gid_t ogid;
    gid_t pgid;
    irqstate_t flags;
    int ret;
  
    /* Disable interrupts so that nothing can change in the relationship of
     * the three task:  Child, current parent, and new parent.
     */
  
    flags = enter_critical_section();
  
    /* Get the child tasks task group */
  
    tcb = sched_gettcb(chpid);
    if (!tcb)
      {
        ret = -ECHILD;
        goto errout_with_ints;
      }
  
    DEBUGASSERT(tcb->group);
    chgrp = tcb->group;
  
    /* Get the GID of the old parent task's task group (ogid) */
  
    ogid = chgrp->tg_pgid;
  
    /* Get the old parent task's task group (ogrp) */
  
    ogrp = group_findbygid(ogid);
    if (!ogrp)
      {
        ret = -ESRCH;
        goto errout_with_ints;
      }
  
    /* If new parent task's PID (ppid) is zero, then new parent is the
     * grandparent will be the new parent, i.e., the parent of the current
     * parent task.
     */
  
    if (ppid == 0)
      {
        /* Get the grandparent task's task group (pgrp) */
  
        pgid = ogrp->tg_pgid;
        pgrp = group_findbygid(pgid);
      }
    else
      {
        /* Get the new parent task's task group (pgrp) */
  
        tcb = sched_gettcb(ppid);
        if (!tcb)
          {
            ret = -ESRCH;
            goto errout_with_ints;
          }
  
        pgrp = tcb->group;
        pgid = pgrp->tg_gid;
      }
  
    if (!pgrp)
      {
        ret = -ESRCH;
        goto errout_with_ints;
      }
  
    /* Then reparent the child.  Notice that we don't actually change the
     * parent of the task. Rather, we change the parent task group for
     * all members of the child's task group.
     */
  
    chgrp->tg_pgid = pgid;
  
  #ifdef CONFIG_SCHED_CHILD_STATUS
    /* Remove the child status entry from old parent task group */
  
    child = group_removechild(ogrp, chpid);
    if (child)
      {
        /* Has the new parent's task group supressed child exit status? */
  
        if ((pgrp->tg_flags && GROUP_FLAG_NOCLDWAIT) == 0)
          {
            /* No.. Add the child status entry to the new parent's task group */
  
            group_addchild(pgrp, child);
          }
        else
          {
            /* Yes.. Discard the child status entry */
  
            group_freechild(child);
          }
  
        /* Either case is a success */
  
        ret = OK;
      }
    else
      {
        /* This would not be an error if the original parent's task group has
         * suppressed child exit status.
         */
  
        ret = ((ogrp->tg_flags && GROUP_FLAG_NOCLDWAIT) == 0) ? -ENOENT : OK;
      }
  
  #else /* CONFIG_SCHED_CHILD_STATUS */
    /* Child task exit status is not retained */
  
    DEBUGASSERT(ogrp->tg_nchildren > 0);
  
    ogrp->tg_nchildren--;  /* The orignal parent now has one few children */
    pgrp->tg_nchildren++;  /* The new parent has one additional child */
    ret = OK;
  
  #endif /* CONFIG_SCHED_CHILD_STATUS */
  
  errout_with_ints:
    leave_critical_section(flags);
    return ret;
  }
  #else
  int task_reparent(pid_t ppid, pid_t chpid)
  {
  #ifdef CONFIG_SCHED_CHILD_STATUS
    FAR struct child_status_s *child;
  #endif
    struct tcb_s *ptcb;
    struct tcb_s *chtcb;
    struct tcb_s *otcb;
    pid_t opid;
    irqstate_t flags;
    int ret;
  
    /* Disable interrupts so that nothing can change in the relationship of
     * the three task:  Child, current parent, and new parent.
     */
  
    flags = enter_critical_section();
  
    /* Get the child tasks TCB (chtcb) */
  
    chtcb = sched_gettcb(chpid);
    if (!chtcb)
      {
        ret = -ECHILD;
        goto errout_with_ints;
      }
  
    /* Get the PID of the child task's parent (opid) */
  
    opid = chtcb->group->tg_ppid;
  
    /* Get the TCB of the child task's parent (otcb) */
  
    otcb = sched_gettcb(opid);
    if (!otcb)
      {
        ret = -ESRCH;
        goto errout_with_ints;
      }
  
    /* If new parent task's PID (tg_ppid) is zero, then new parent is the
     * grandparent will be the new parent, i.e., the parent of the current
     * parent task.
     */
  
    if (ppid == 0)
      {
        ppid = otcb->group->tg_ppid;
      }
  
    /* Get the new parent task's TCB (ptcb) */
  
    ptcb = sched_gettcb(ppid);
    if (!ptcb)
      {
        ret = -ESRCH;
        goto errout_with_ints;
      }
  
    /* Then reparent the child.  The task specified by ppid is the new parent. */
  
    chtcb->group->tg_ppid = ppid;
  
  #ifdef CONFIG_SCHED_CHILD_STATUS
    /* Remove the child status entry from old parent TCB */
  
    child = group_removechild(otcb->group, chpid);
    if (child)
      {
        /* Has the new parent's task group supressed child exit status? */
  
        if ((ptcb->group->tg_flags && GROUP_FLAG_NOCLDWAIT) == 0)
          {
            /* No.. Add the child status entry to the new parent's task group */
  
            group_addchild(ptcb->group, child);
          }
        else
          {
            /* Yes.. Discard the child status entry */
  
            group_freechild(child);
          }
  
        /* Either case is a success */
  
        ret = OK;
      }
    else
      {
        /* This would not be an error if the original parent's task group has
         * suppressed child exit status.
         */
  
        ret = ((otcb->group->tg_flags && GROUP_FLAG_NOCLDWAIT) == 0) ? -ENOENT : OK;
      }
  
  #else /* CONFIG_SCHED_CHILD_STATUS */
    /* Child task exit status is not retained */
  
    DEBUGASSERT(otcb->group != NULL && otcb->group->tg_nchildren > 0);
  
    otcb->group->tg_nchildren--;  /* The orignal parent now has one few children */
    ptcb->group->tg_nchildren++;  /* The new parent has one additional child */
    ret = OK;
  
  #endif /* CONFIG_SCHED_CHILD_STATUS */
  
  errout_with_ints:
    leave_critical_section(flags);
    return ret;
  }
  #endif
  #endif /* CONFIG_SCHED_HAVE_PARENT */
  