sched/task_reparent.c - nuttx - Git at Google

 /*****************************************************************************
  * sched/task_reparent.c
  *
  *   Copyright (C) 2013 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 "os_internal.h"
 #include "group_internal.h"

 #ifdef CONFIG_SCHED_HAVE_PARENT

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

 /*****************************************************************************
  * 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 relatinoship of
    * the three task:  Child, current parent, and new parent.
    */

   flags = irqsave();

   /* 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 */

   DEBUGASSERT(otcb->nchildren > 0);

   otcb->nchildren--;     /* The orignal parent now has one few children */
   ptcb->nchildren++;     /* The new parent has one additional child */
   ret = OK;

 #endif /* CONFIG_SCHED_CHILD_STATUS */

 errout_with_ints:
   irqrestore(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 relatinoship of
    * the three task:  Child, current parent, and new parent.
    */

   flags = irqsave();

   /* 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->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 (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->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 */

   chtcb->ppid = ppid;  /* The task specified by ppid is the new parent */

 #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 */

   DEBUGASSERT(otcb->nchildren > 0);

   otcb->nchildren--;     /* The orignal parent now has one few children */
   ptcb->nchildren++;     /* The new parent has one additional child */
   ret = OK;

 #endif /* CONFIG_SCHED_CHILD_STATUS */

 errout_with_ints:
   irqrestore(flags);
   return ret;
 }
 #endif
 #endif /* CONFIG_SCHED_HAVE_PARENT */
	/*****************************************************************************
	* sched/task_reparent.c
	*
	* Copyright (C) 2013 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 "os_internal.h"
	#include "group_internal.h"

	#ifdef CONFIG_SCHED_HAVE_PARENT

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

	/*****************************************************************************
	* 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 relatinoship of
	* the three task: Child, current parent, and new parent.
	*/

	flags = irqsave();

	/* 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 */

	DEBUGASSERT(otcb->nchildren > 0);

	otcb->nchildren--; /* The orignal parent now has one few children */
	ptcb->nchildren++; /* The new parent has one additional child */
	ret = OK;

	#endif /* CONFIG_SCHED_CHILD_STATUS */

	errout_with_ints:
	irqrestore(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 relatinoship of
	* the three task: Child, current parent, and new parent.
	*/

	flags = irqsave();

	/* 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->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 (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->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 */

	chtcb->ppid = ppid; /* The task specified by ppid is the new parent */

	#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 */

	DEBUGASSERT(otcb->nchildren > 0);

	otcb->nchildren--; /* The orignal parent now has one few children */
	ptcb->nchildren++; /* The new parent has one additional child */
	ret = OK;

	#endif /* CONFIG_SCHED_CHILD_STATUS */

	errout_with_ints:
	irqrestore(flags);
	return ret;
	}
	#endif
	#endif /* CONFIG_SCHED_HAVE_PARENT */