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nuttx/sched/task/task_reparent.c

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/****************************************************************************
* sched/task/task_reparent.c
*
* Copyright (C) 2013, 2016, 2019 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 <nuttx/sched.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.
*
* Input 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.
*
* Returned 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;
FAR struct tcb_s *tcb;
grpid_t ogrpid;
grpid_t pgrpid;
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 (ogrpid) */
ogrpid = chgrp->tg_pgrpid;
/* Get the old parent task's task group (ogrp) */
ogrp = group_findby_grpid(ogrpid);
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) */
pgrpid = ogrp->tg_pgrpid;
pgrp = group_findby_grpid(pgrpid);
}
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;
pgrpid = pgrp->tg_grpid;
}
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_pgrpid = pgrpid;
#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
FAR struct tcb_s *ptcb;
FAR struct tcb_s *chtcb;
FAR 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 */
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