/****************************************************************************
 *  sched/group/group_addrenv.c
 *
 *   Copyright (C) 2014 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 <debug.h>

#include <nuttx/sched.h>

#include "sched/sched.h"
#include "group/group.h"

#ifdef CONFIG_ARCH_ADDRENV

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

/****************************************************************************
 * Public Data
 ****************************************************************************/
/* This variable holds the group ID of the current task group.  This ID is
 * zero if the current task is a kernel thread that has no address
 * environment (other than the kernel context).
 *
 * This must only be accessed with interrupts disabled.
 */

gid_t g_gid_current;

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

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

/****************************************************************************
 * Name: group_addrenv
 *
 * Description:
 *   Instantiate the group address environment for the current thread at the
 *   the head of the ready to run list.
 *
 *   This function is called from platform-specific code after any context
 *   switch (i.e., after any change in the thread at the head of the ready-to-
 *   run list).  This function will change the address environment if the
 *   new thread is part of a different task group.
 *
 * Parameters:
 *   tcb - The TCB of thread that needs an address environment.  This should
 *         be the TCB at the head of the ready-to-run list, but that is not
 *         enough.
 *
 * Return Value:
 *   Zero (OK) is returned on success.  A negated errno value is returned on
 *   any failure.
 *
 * Assumptions:
 *   This function should only be called within critical OS sections with
 *   interrupts disabled.  Interrupts are disabled internally just to be
 *   certain, however.
 *
 ****************************************************************************/

int group_addrenv(FAR struct tcb_s *tcb)
{
  FAR struct task_group_s *group;
  FAR struct task_group_s *oldgroup;
  irqstate_t flags;
  gid_t gid;
  int ret;

  /* NULL for the tcb means to use the TCB of the task at the head of the
   * ready to run list.
   */

  if (!tcb)
    {
      tcb = (FAR struct tcb_s *)g_readytorun.head;
    }

  DEBUGASSERT(tcb && tcb->group);
  group = tcb->group;

  /* Does the group have an address environment? */

  if ((group->tg_flags & GROUP_FLAG_ADDRENV) == 0)
    {
      /* No... just return perhaps leaving a different address environment
       * intact.
       */

      return OK;
    }

  /* Get the ID of the group that needs the address environment */

  gid = group->tg_gid;
  DEBUGASSERT(gid != 0);

  /* Are we going to change address environments? */

  flags = irqsave();
  if (gid != g_gid_current)
    {
      /* Yes.. Is there a current address environment in place? */

      if (g_gid_current != 0)
        {
          /* Find the old group with this ID. */

          oldgroup = group_findbygid(g_gid_current);
          DEBUGASSERT(oldgroup &&
                     (oldgroup->tg_flags & GROUP_FLAG_ADDRENV) != 0);

          if (oldgroup)
            {
              /* We need to flush the D-Cache and Invalidate the I-Cache for
               * the group whose environment is disappearing.
               */

              up_addrenv_coherent(&oldgroup->tg_addrenv);
            }
        }

      /* Instantiate the new address environment (removing the old
       * environment in the process).  For the case of kernel threads,
       * the old mappings will be removed and no new mappings will be
       * instantiated.
       */

      ret = up_addrenv_select(&group->tg_addrenv, NULL);
      if (ret < 0)
        {
          bdbg("ERROR: up_addrenv_select failed: %d\n", ret);
        }

      /* Save the new, current group */
  
      g_gid_current = gid;
    }

  irqrestore(flags);
  return OK;
}

#endif /* CONFIG_ARCH_ADDRENV */
