/****************************************************************************
 * sched/group/group_signal.c
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <sched.h>
#include <assert.h>
#include <signal.h>
#include <errno.h>
#include <debug.h>

#include <nuttx/signal.h>

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

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

#ifdef HAVE_GROUP_MEMBERS
struct group_signal_s
{
  FAR siginfo_t *siginfo; /* Signal to be dispatched */
  FAR struct tcb_s *dtcb; /* Default, valid TCB */
  FAR struct tcb_s *utcb; /* TCB with this signal unblocked */
  FAR struct tcb_s *atcb; /* This TCB was awakened */
  FAR struct tcb_s *ptcb; /* This TCB received the signal */
};
#endif

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

/****************************************************************************
 * Name: group_signal_handler
 *
 * Description:
 *   Callback from group_foreachchild that handles one member of the group.
 *
 * Input Parameters:
 *   pid - The ID of the group member that may be signalled.
 *   arg - A pointer to a struct group_signal_s instance.
 *
 * Returned Value:
 *   0 (OK) on success; a negated errno value on failure.
 *
 ****************************************************************************/

#ifdef HAVE_GROUP_MEMBERS
static int group_signal_handler(pid_t pid, FAR void *arg)
{
  FAR struct group_signal_s *info = (FAR struct group_signal_s *)arg;
  FAR struct tcb_s *tcb;
  FAR sigactq_t *sigact;
  int ret;

  /* Get the TCB associated with the group member */

  tcb = nxsched_get_tcb(pid);
  DEBUGASSERT(tcb != NULL && tcb->group != NULL && info != NULL);

  if (tcb)
    {
      /* Set this one as the default if we have not already set the
       * default.
       */

      if (!info->dtcb)
        {
          info->dtcb = tcb;
        }

      /* Is the thread waiting for this signal (in this case, the signal is
       * probably blocked).
       */

      ret = nxsig_ismember(&tcb->sigwaitmask, info->siginfo->si_signo);
      if (ret == 1 && (!info->atcb || info->siginfo->si_signo == SIGCHLD))
        {
          /* Yes.. This means that the task is suspended, waiting for this
           * signal to occur. Stop looking and use this TCB.  The
           * requirement is this:  If a task group receives a signal and
           * more than one thread is waiting on that signal, then one and
           * only one indeterminate thread out of that waiting group will
           * receive the signal.
           */

          ret = nxsig_tcbdispatch(tcb, info->siginfo);
          if (ret < 0)
            {
              return ret;
            }

          /* Limit to one thread */

          info->atcb = tcb;

          if (info->ptcb != NULL && info->siginfo->si_signo != SIGCHLD)
            {
              return 1; /* Terminate the search */
            }
        }

      /* Is this signal unblocked on this thread? */

      if (!nxsig_ismember(&tcb->sigprocmask, info->siginfo->si_signo) &&
          !info->ptcb && tcb != info->atcb)
        {
          /* Yes.. remember this TCB if we have not encountered any
           * other threads that have the signal unblocked.
           */

          if (!info->utcb)
            {
              info->utcb = tcb;
            }

          /* Is there also a action associated with the task group? */

          sigact = nxsig_find_action(tcb->group, info->siginfo->si_signo);
          if (sigact)
            {
              /* Yes.. then use this thread.  The requirement is this:
               * If a task group receives a signal then one and only one
               * indeterminate thread in the task group which is not
               * blocking the signal will receive the signal.
               */

              ret = nxsig_tcbdispatch(tcb, info->siginfo);
              if (ret < 0)
                {
                  return ret;
                }

              /* Limit to one thread */

              info->ptcb = tcb;
              if (info->atcb != NULL)
                {
                  return 1; /* Terminate the search */
                }
            }
        }
    }

  return 0; /* Keep searching */
}
#endif

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

/****************************************************************************
 * Name: group_signal
 *
 * Description:
 *   Send a signal to every member of the group.
 *
 * Input Parameters:
 *   group - The task group that needs to be signalled.
 *
 * Returned Value:
 *   0 (OK) on success; a negated errno value on failure.
 *
 * Assumptions:
 *   Called during task termination in a safe context. No special precautions
 *   are required here.  Because signals can be sent from interrupt handlers,
 *   this function may be called indirectly in the context of an interrupt
 *   handler.
 *
 ****************************************************************************/

int group_signal(FAR struct task_group_s *group, FAR siginfo_t *siginfo)
{
#ifdef HAVE_GROUP_MEMBERS
  struct group_signal_s info;
  FAR struct tcb_s *tcb;
  int ret;

  DEBUGASSERT(group && siginfo);

  info.siginfo = siginfo;
  info.dtcb    = NULL;     /* Default, valid TCB */
  info.utcb    = NULL;     /* TCB with this signal unblocked */
  info.atcb    = NULL;     /* This TCB was awakened */
  info.ptcb    = NULL;     /* This TCB received the signal */

  /* Make sure that pre-emption is disabled to that we signal all of the
   * members of the group before any of them actually run. (This does
   * nothing if were were called from an interrupt handler).
   */

#ifdef CONFIG_SMP
  irqstate_t flags = enter_critical_section();
#else
  sched_lock();
#endif

  /* Now visit each member of the group and perform signal handling checks. */

  ret = group_foreachchild(group, group_signal_handler, &info);
  if (ret < 0)
    {
      goto errout;
    }

  /* We need to dispatch the signal in any event (if nothing else so that it
   * can be added to the pending signal list). If we found a thread with the
   * signal unblocked, then use that thread.
   */

  if (info.atcb == NULL && info.ptcb == NULL)
    {
      if (info.utcb)
        {
          tcb = info.utcb;
        }

      /* Otherwise use the default TCB.  There should always be a default
       * TCB. It will have the signal blocked, but can be used to get the
       * signal to a pending state.
       */

      else if (info.dtcb)
        {
          tcb = info.dtcb;
        }
      else
        {
          ret = -ECHILD;
          goto errout;
        }

      /* Now deliver the signal to the selected group member */

      ret = nxsig_tcbdispatch(tcb, siginfo);
    }

errout:
#ifdef CONFIG_SMP
  leave_critical_section(flags);
#else
  sched_unlock();
#endif
  return ret;

#else

  UNUSED(group);
  UNUSED(siginfo);
  return -ENOSYS;

#endif
}