/* Copyright (c) 2014, 2015, Oracle and/or its affiliates. All rights reserved.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */

#include "my_thread.h"          /* my_thread_id */
#include "my_timer.h"           /* my_timer_t */
#include "sql_class.h"          /* THD */
#include "sql_timer.h"          /* thd_timer_set, etc. */
#include "sql_parse.h"          /* Global_THD_manager, Find_thd_with_id */
#include "mysqld.h"

struct st_thd_timer_info
{
  my_thread_id thread_id;
  my_timer_t timer;
  mysql_mutex_t mutex;
  bool destroy;
};

C_MODE_START
static void timer_callback(my_timer_t *);
C_MODE_END

/**
  Allocate and initialize a thread timer object.

  @return NULL on failure.
*/

static THD_timer_info *
thd_timer_create(void)
{
  THD_timer_info *thd_timer;
  DBUG_ENTER("thd_timer_create");

  thd_timer= (THD_timer_info *) my_malloc(key_memory_thd_timer,
                                       sizeof(THD_timer_info),
                                       MYF(MY_WME));

  if (thd_timer == NULL)
    DBUG_RETURN(NULL);

  thd_timer->thread_id= 0;
  mysql_mutex_init(key_thd_timer_mutex, &thd_timer->mutex, MY_MUTEX_INIT_FAST);
  thd_timer->destroy= 0;
  thd_timer->timer.notify_function= timer_callback;

  if (DBUG_EVALUATE_IF("thd_timer_create_failure", 0, 1) &&
      ! my_timer_create(&thd_timer->timer))
    DBUG_RETURN(thd_timer);

  mysql_mutex_destroy(&thd_timer->mutex);
  my_free(thd_timer);

  DBUG_RETURN(NULL);
}


/**
  Notify a thread (session) that its timer has expired.

  @param  thd_timer   Thread timer object.

  @return true if the object should be destroyed.
*/

static bool
timer_notify(THD_timer_info *thd_timer)
{
  Find_thd_with_id find_thd_with_id(thd_timer->thread_id);
  THD *thd= Global_THD_manager::get_instance()->find_thd(&find_thd_with_id);

  DBUG_ASSERT(!thd_timer->destroy || !thd_timer->thread_id);
  /*
    Statement might have finished while the timer notification
    was being delivered. If this is the case, the timer object
    was detached (orphaned) and has no associated session (thd).
  */
  if (thd)
  {
    /* process only if thread is not already undergoing any kill connection. */
    if (thd->killed != THD::KILL_CONNECTION)
    {
      thd->awake(THD::KILL_TIMEOUT);
    }
    mysql_mutex_unlock(&thd->LOCK_thd_data);
  }

  /* Mark the object as unreachable. */
  thd_timer->thread_id= 0;

  return thd_timer->destroy;
}


/**
  Timer expiration notification callback.

  @param  timer   Timer (mysys) object.

  @note Invoked in a separate thread of control.
*/

static void
timer_callback(my_timer_t *timer)
{
  bool destroy;
  THD_timer_info *thd_timer;

  thd_timer= my_container_of(timer, THD_timer_info, timer);

  mysql_mutex_lock(&thd_timer->mutex);
  destroy= timer_notify(thd_timer);
  mysql_mutex_unlock(&thd_timer->mutex);

  if (destroy)
    thd_timer_destroy(thd_timer);
}


/**
  Set the time until the currently running statement is aborted.

  @param  thd         Thread (session) context.
  @param  thd_timer   Thread timer object.
  @param  time        Length of time, in milliseconds, until the currently
                      running statement is aborted.

  @return NULL on failure.
*/

THD_timer_info *
thd_timer_set(THD *thd, THD_timer_info *thd_timer, unsigned long time)
{
  DBUG_ENTER("thd_timer_set");

  /* Create a new thread timer object if one was not provided. */
  if (thd_timer == NULL && (thd_timer= thd_timer_create()) == NULL)
    DBUG_RETURN(NULL);

  DBUG_ASSERT(!thd_timer->destroy && !thd_timer->thread_id);

  /* Mark the notification as pending. */
  thd_timer->thread_id= thd->thread_id();

  /* Arm the timer. */
  if (DBUG_EVALUATE_IF("thd_timer_set_failure", 0, 1) &&
      !my_timer_set(&thd_timer->timer, time))
    DBUG_RETURN(thd_timer);

  /* Dispose of the (cached) timer object. */
  thd_timer_destroy(thd_timer);

  DBUG_RETURN(NULL);
}


/**
  Reap a (possibly) pending timer object.

  @param  thd_timer   Thread timer object.

  @return true if the timer object is unreachable.
*/

static bool
reap_timer(THD_timer_info *thd_timer, bool pending)
{
  /* Cannot be tagged for destruction. */
  DBUG_ASSERT(!thd_timer->destroy);

  /* If not pending, timer hasn't fired. */
  DBUG_ASSERT(pending || thd_timer->thread_id);

  /*
    The timer object can be reused if the timer was stopped before
    expiring. Otherwise, the timer notification function might be
    executing asynchronously in the context of a separate thread.
  */
  bool unreachable= pending ? thd_timer->thread_id == 0 : true;

  thd_timer->thread_id= 0;

  return unreachable;
}

/**
  Deactivate the given timer.

  @param  thd_timer   Thread timer object.

  @return NULL if the timer object was orphaned.
          Otherwise, the given timer object is returned.
*/

THD_timer_info *
thd_timer_reset(THD_timer_info *thd_timer)
{
  bool unreachable;
  int status, state;
  DBUG_ENTER("thd_timer_cancel");

  status= my_timer_cancel(&thd_timer->timer, &state);

  /*
    If the notification function cannot possibly run anymore, cache
    the timer object as there are no outstanding references to it.
  */
  mysql_mutex_lock(&thd_timer->mutex);
  unreachable= reap_timer(thd_timer, status ? true : !state);
  thd_timer->destroy= !unreachable;
  mysql_mutex_unlock(&thd_timer->mutex);

  DBUG_RETURN(unreachable ? thd_timer : NULL);
}


/**
  Release resources allocated for a thread timer.

  @param  thd_timer   Thread timer object.
*/

void
thd_timer_destroy(THD_timer_info *thd_timer)
{
  DBUG_ENTER("thd_timer_destroy");

  my_timer_delete(&thd_timer->timer);
  mysql_mutex_destroy(&thd_timer->mutex);
  my_free(thd_timer);

  DBUG_VOID_RETURN;
}