/*****************************************************************************
 * sched/group_leave.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 <sched.h>
#include <assert.h>
#include <errno.h>
#include <debug.h>

#include <nuttx/fs/fs.h>
#include <nuttx/net/net.h>
#include <nuttx/lib.h>

#include "env_internal.h"
#include "sig_internal.h"
#include "pthread_internal.h"
#include "mq_internal.h"
#include "group_internal.h"

#ifdef HAVE_TASK_GROUP

/*****************************************************************************
 * Pre-processor Definitions
 *****************************************************************************/

/*****************************************************************************
 * Private Types
 *****************************************************************************/

/*****************************************************************************
 * Private Data
 *****************************************************************************/

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

/*****************************************************************************
 * Name: group_remove
 *
 * Description:
 *   Remove a group from the list of groups.
 *
 * Parameters:
 *   group - The group to be removed.
 *
 * Return Value:
 *   None.
 *
 * Assumptions:
 *   Called during task deletion in a safe context.  No special precautions
 *   are required here.
 *
 *****************************************************************************/

#ifdef HAVE_GROUP_MEMBERS
void group_remove(FAR struct task_group_s *group)
{
  FAR struct task_group_s *curr;
  FAR struct task_group_s *prev;
  irqstate_t flags;

  /* Let's be especially careful while access the global task group list.
   * This is probably un-necessary.
   */
 
  flags = irqsave();
 
  /* Find the task group structure */

  for (prev = NULL, curr = g_grouphead;
       curr && curr != group;
       prev = curr, curr = curr->flink);

  /* Did we find it?  If so, remove it from the list. */

  if (curr)
    {
      /* Do we remove it from mid-list?  Or from the head of the list? */

      if (prev)
        {
          prev->flink = curr->flink;
        }
      else
        {
          g_grouphead = curr->flink;
        }

      curr->flink = NULL;
    }

  irqrestore(flags);
}
#endif

/*****************************************************************************
 * Name: group_release
 *
 * Description:
 *   Release group resources after the last member has left the group.
 *
 * Parameters:
 *   group - The group to be removed.
 *
 * Return Value:
 *   None.
 *
 * Assumptions:
 *   Called during task deletion in a safe context.  No special precautions
 *   are required here.
 *
 *****************************************************************************/

static inline void group_release(FAR struct task_group_s *group)
{
  /* Free all un-reaped child exit status */

#if defined(CONFIG_SCHED_HAVE_PARENT) && defined(CONFIG_SCHED_CHILD_STATUS)
  group_removechildren(group);
#endif

#ifndef CONFIG_DISABLE_SIGNALS
  /* Release pending signals */

  sig_release(group);
#endif

#ifndef CONFIG_DISABLE_PTHREAD
  /* Release pthread resources */

  pthread_release(group);
#endif

  /* Free all file-related resources now.  We really need to close files as
   * soon as possible while we still have a functioning task.
   */

#if CONFIG_NFILE_DESCRIPTORS > 0
  /* Free resources held by the file descriptor list */

  files_releaselist(&group->tg_filelist);

#if CONFIG_NFILE_STREAMS > 0
  /* Free resource held by the stream list */

  lib_releaselist(&group->tg_streamlist);

#endif /* CONFIG_NFILE_STREAMS */
#endif /* CONFIG_NFILE_DESCRIPTORS */

#if CONFIG_NSOCKET_DESCRIPTORS > 0
  /* Free resource held by the socket list */

  net_releaselist(&group->tg_socketlist);
#endif /* CONFIG_NSOCKET_DESCRIPTORS */

  /* Release all shared environment variables */

#ifndef CONFIG_DISABLE_ENVIRON
  env_release(group);
#endif

  /* Close message queues opened by members of the group */

#ifndef CONFIG_DISABLE_MQUEUE
  mq_release(group);
#endif

#ifdef HAVE_GROUP_MEMBERS
  /* Remove the group from the list of groups */

  group_remove(group);

  /* Release the members array */

  if (group->tg_members)
    {
      sched_kfree(group->tg_members);
      group->tg_members = NULL;
    }
#endif

  /* Release the group container itself */

  sched_kfree(group);
}

/*****************************************************************************
 * Name: group_removemember
 *
 * Description:
 *   Remove a member from a group.
 *
 * Parameters:
 *   group - The group from which to remove the member.
 *   pid - The member to be removed.
 *
 * Return Value:
 *   On success, returns the number of members remaining in the group (>=0).
 *   Can fail only if the member is not found in the group.  On failure,
 *   returns -ENOENT
 *
 * Assumptions:
 *   Called during task deletion and also from the reparenting logic, both
 *   in a safe context.  No special precautions are required here.
 *
 *****************************************************************************/

#ifdef HAVE_GROUP_MEMBERS
static inline void group_removemember(FAR struct task_group_s *group, pid_t pid)
{
  irqstate_t flags;
  int i;

  DEBUGASSERT(group);

  /* Find the member in the array of members and remove it */

  for (i = 0; i < group->tg_nmembers; i++)
    {
      /* Does this member have the matching pid */

      if (group->tg_members[i] == pid)
       {
          /* Remove the member from the array of members.  This must be an
           * atomic operation because the member array may be accessed from
           * interrupt handlers (read-only).
           */

          flags = irqsave();
          group->tg_members[i] = group->tg_members[group->tg_nmembers - 1];
          group->tg_nmembers--;
          irqrestore(flags);
        }
    }
}
#endif /* HAVE_GROUP_MEMBERS */

/*****************************************************************************
 * Public Functions
 *****************************************************************************/

/*****************************************************************************
 * Name: group_leave
 *
 * Description:
 *   Release a reference on a group.  This function is called when a task or
 *   thread exits.  It decrements the reference count on the group.  If the
 *   reference count decrements to zero, then it frees the group and all of
 *   resources contained in the group.
 *
 * Parameters:
 *   tcb - The TCB of the task that is exiting.
 *
 * Return Value:
 *   None.
 *
 * Assumptions:
 *   Called during task deletion in a safe context.  No special precautions
 *   are required here.
 *
 *****************************************************************************/

#ifdef HAVE_GROUP_MEMBERS
void group_leave(FAR struct tcb_s *tcb)
{
  FAR struct task_group_s *group;

  DEBUGASSERT(tcb);

  /* Make sure that we have a group. */

  group = tcb->group;
  if (group)
    {
      /* Remove the member from group.  This function may be called
       * during certain error handling before the PID has been
       * added to the group.  In this case tcb->pid will be uninitialized
       * group_removemember() will fail.
       */

      group_removemember(group, tcb->pid);

      /* Have all of the members left the group? */

      if (group->tg_nmembers == 0)
        {
          /* Yes.. Release all of the resource held by the task group */

          group_release(group);
        }

      /* In any event, we can detach the group from the TCB so that we won't
       * do this again.
       */

      tcb->group = NULL;
    }
}

#else /* HAVE_GROUP_MEMBERS */

void group_leave(FAR struct tcb_s *tcb)
{
  FAR struct task_group_s *group;

  DEBUGASSERT(tcb);

  /* Make sure that we have a group */

  group = tcb->group;
  if (group)
    {
      /* Yes, we have a group.. Is this the last member of the group? */

      if (group->tg_nmembers > 1)
        {
          /* No.. just decrement the number of members in the group */

          group->tg_nmembers--;
        }

      /* Yes.. that was the last member remaining in the group */

      else
        {
          /* Release all of the resource held by the task group */

          group_release(group);
        }

      /* In any event, we can detach the group from the TCB so we won't do
       * this again.
       */

      tcb->group = NULL;
    }
}

#endif /* HAVE_GROUP_MEMBERS */
#endif /* HAVE_TASK_GROUP */