WL#3337 (Event scheduler new architecture)

This patch makes the relationship between Event_scheduler and Event_queue
unidirectional from the former to the latter.




The change is that the conditional on which the scheduler sleeped has been
moved to the Event_queue and the latter does not call anymore
Event_scheduler::queue_changed(), which in turn has be removed.

sql/event_queue.cc

@@ -18,7 +18,6 @@
 #include "event_queue.h"
 #include "event_data_objects.h"
 #include "event_db_repository.h"
-#include "event_scheduler.h"
 
 
 #define EVENT_QUEUE_INITIAL_SIZE 30
@@ -87,6 +86,7 @@ Event_queue::Event_queue()
 {
   mutex_last_unlocked_in_func= mutex_last_locked_in_func=
     mutex_last_attempted_lock_in_func= "";
+  set_zero_time(&next_activation_at, MYSQL_TIMESTAMP_DATETIME);
 }
 
 
@@ -135,8 +135,7 @@ Event_queue::deinit_mutexes()
 */
 
 bool
-Event_queue::init_queue(THD *thd, Event_db_repository *db_repo,
-                        Event_scheduler *sched)
+Event_queue::init_queue(THD *thd, Event_db_repository *db_repo)
 {
   pthread_t th;
   bool res;
@@ -147,7 +146,6 @@ Event_queue::init_queue(THD *thd, Event_db_repository *db_repo,
 
   LOCK_QUEUE_DATA();
   db_repository= db_repo;
-  scheduler= sched;
 
   if (init_queue_ex(&queue, EVENT_QUEUE_INITIAL_SIZE , 0 /*offset*/,
                     0 /*max_on_top*/, event_queue_element_compare_q,
@@ -233,9 +231,8 @@ Event_queue::create_event(THD *thd, LEX_STRING dbname, LEX_STRING name)
     DBUG_PRINT("info", ("new event in the queue 0x%lx", new_element));
     queue_insert_safe(&queue, (byte *) new_element);
     dbug_dump_queue(thd->query_start());
+    pthread_cond_broadcast(&COND_queue_state);  
     UNLOCK_QUEUE_DATA();
-
-    notify_observers();
   }
 
   DBUG_RETURN(res);
@@ -298,13 +295,12 @@ Event_queue::update_event(THD *thd, LEX_STRING dbname, LEX_STRING name,
   {
     DBUG_PRINT("info", ("new event in the Q 0x%lx", new_element));
     queue_insert_safe(&queue, (byte *) new_element);
+    pthread_cond_broadcast(&COND_queue_state);  
   }
+
   dbug_dump_queue(thd->query_start());
   UNLOCK_QUEUE_DATA();
 
-  if (new_element)
-    notify_observers();
-
 end:
   DBUG_PRINT("info", ("res=%d", res));
   DBUG_RETURN(res);
@@ -386,7 +382,8 @@ Event_queue::drop_matching_events(THD *thd, LEX_STRING pattern,
       i++;
   }
   /*
-    We don't call notify_observers() . If we remove the top event:
+    We don't call pthread_cond_broadcast(&COND_queue_state);  
+    If we remove the top event:
     1. The queue is empty. The scheduler will wake up at some time and
        realize that the queue is empty. If create_event() comes inbetween
        it will signal the scheduler
@@ -421,24 +418,6 @@ Event_queue::drop_schema_events(THD *thd, LEX_STRING schema)
 }
 
 
-/*
-  Signals the observers (the main scheduler thread) that the
-  state of the queue has been changed.
-
-  SYNOPSIS
-    Event_queue::notify_observers()
-*/
-
-void
-Event_queue::notify_observers()
-{
-  DBUG_ENTER("Event_queue::notify_observers");
-  DBUG_PRINT("info", ("Signalling change of the queue"));
-  scheduler->queue_changed();
-  DBUG_VOID_RETURN;
-}
-
-
 /*
   Searches for an event in the queue
 
@@ -701,6 +680,8 @@ Event_queue::dbug_dump_queue(time_t now)
 #endif
 }
 
+static const char *queue_empty_msg= "Waiting on empty queue";
+static const char *queue_wait_msg= "Waiting for next activation";
 
 /*
   Checks whether the top of the queue is elligible for execution and
@@ -725,39 +706,62 @@ Event_queue::dbug_dump_queue(time_t now)
 */
 
 bool
-Event_queue::get_top_for_execution_if_time(THD *thd, time_t now,
-                                           Event_job_data **job_data,
-                                           struct timespec *abstime)
+Event_queue::get_top_for_execution_if_time(THD *thd, Event_job_data **job_data)
 {
   bool ret= FALSE;
   struct timespec top_time;
+  struct timespec *abstime;
   *job_data= NULL;
   DBUG_ENTER("Event_queue::get_top_for_execution_if_time");
-  DBUG_PRINT("enter", ("thd=0x%lx now=%d", thd, now));
-  abstime->tv_nsec= 0;
+
+  top_time.tv_nsec= 0;
   LOCK_QUEUE_DATA();
-  do {
+  for (;;)
+  {
     int res;
-    if (!queue.elements)
-    {
-      abstime->tv_sec= 0;
-      break;
-    }
+    Event_queue_element *top= NULL;
 
-    Event_queue_element *top= ((Event_queue_element*) queue_element(&queue, 0));
+    thd->end_time();
+    time_t now= thd->query_start();
+    abstime= NULL;
 
-    top_time.tv_sec= sec_since_epoch_TIME(&top->execute_at);
+    if (queue.elements)
+    {
+      top= ((Event_queue_element*) queue_element(&queue, 0));
+      top_time.tv_sec= sec_since_epoch_TIME(&top->execute_at);
 
-    if (top_time.tv_sec > now)
+      abstime= &top_time;
+    }
+
+    if (!abstime || abstime->tv_sec > now)
     {
-      abstime->tv_sec= top_time.tv_sec;
-      DBUG_PRINT("info", ("Have to wait %d till %d", abstime->tv_sec - now,
-                 abstime->tv_sec));
-      break;
+      const char *msg;
+      if (abstime)
+      {
+        next_activation_at= top->execute_at;
+        msg= queue_wait_msg;
+      }
+      else
+      {
+        set_zero_time(&next_activation_at, MYSQL_TIMESTAMP_DATETIME);
+        msg= queue_wait_msg;
+      }
+
+      cond_wait(thd, abstime, msg, SCHED_FUNC, __LINE__);
+      if (thd->killed)
+      {
+        DBUG_PRINT("info", ("thd->killed=%d", thd->killed));
+        goto end;
+      }
+      /*
+        The queue could have been emptied. Therefore it's safe to start from
+        the beginning. Moreover, this way we will get also the new top, if
+        the element at the top has been changed.
+      */
+      continue;
     }
 
     DBUG_PRINT("info", ("Ready for execution"));
-    abstime->tv_sec= 0;
     if (!(*job_data= new Event_job_data()))
     {
       ret= TRUE;
@@ -766,6 +770,7 @@ Event_queue::get_top_for_execution_if_time(THD *thd, time_t now,
     if ((res= db_repository->load_named_event(thd, top->dbname, top->name,
                                               *job_data)))
     {
+      DBUG_PRINT("error", ("Got %d from load_named_event", res));
       delete *job_data;
       *job_data= NULL;
       ret= TRUE;
@@ -796,11 +801,13 @@ Event_queue::get_top_for_execution_if_time(THD *thd, time_t now,
       queue_replaced(&queue);
 
     dbug_dump_queue(now);
-  } while (0);
+    break;
+  }
+end:
   UNLOCK_QUEUE_DATA();
   
   DBUG_PRINT("info", ("returning %d. et_new=0x%lx abstime.tv_sec=%d ",
-             ret, *job_data, abstime->tv_sec));
+             ret, *job_data, abstime? abstime->tv_sec:0));
 
   if (*job_data)
     DBUG_PRINT("info", ("db=%s  name=%s definer=%s", (*job_data)->dbname.str,
@@ -864,6 +871,52 @@ Event_queue::unlock_data(const char *func, uint line)
 }
 
 
+/*
+  Wrapper for pthread_cond_wait/timedwait
+
+  SYNOPSIS
+    Event_queue::cond_wait()
+      thd     Thread (Could be NULL during shutdown procedure)
+      msg     Message for thd->proc_info
+      abstime If not null then call pthread_cond_timedwait()
+      func    Which function is requesting cond_wait
+      line    On which line cond_wait is requested
+*/
+
+void
+Event_queue::cond_wait(THD *thd, struct timespec *abstime, const char* msg,
+                       const char *func, uint line)
+{
+  DBUG_ENTER("Event_queue::cond_wait");
+  waiting_on_cond= TRUE;
+  mutex_last_unlocked_at_line= line;
+  mutex_queue_data_locked= FALSE;
+  mutex_last_unlocked_in_func= func;
+
+  thd->enter_cond(&COND_queue_state, &LOCK_event_queue, msg);
+
+  DBUG_PRINT("info", ("pthread_cond_%swait", abstime? "timed":""));
+  if (!abstime)
+    pthread_cond_wait(&COND_queue_state, &LOCK_event_queue);
+  else
+    pthread_cond_timedwait(&COND_queue_state, &LOCK_event_queue, abstime);
+
+  mutex_last_locked_in_func= func;
+  mutex_last_locked_at_line= line;
+  mutex_queue_data_locked= TRUE;
+  waiting_on_cond= FALSE;
+
+  /*
+    This will free the lock so we need to relock. Not the best thing to
+    do but we need to obey cond_wait()
+  */
+  thd->exit_cond("");
+  LOCK_QUEUE_DATA();
+
+  DBUG_VOID_RETURN;
+}
+
+
 /*
   Dumps the internal status of the queue
 
@@ -943,6 +996,28 @@ Event_queue::dump_internal_status(THD *thd)
   protocol->store(&tmp_string);
   ret= protocol->write();
 
+  /* waiting on */
+  protocol->prepare_for_resend();
+  protocol->store(STRING_WITH_LEN("queue waiting on condition"), scs);
+  int_string.set((longlong) waiting_on_cond, scs);
+  protocol->store(&int_string);
+  ret= protocol->write();
+
+  protocol->prepare_for_resend();
+  protocol->store(STRING_WITH_LEN("next activation at"), scs);
+  tmp_string.length(scs->cset->snprintf(scs, (char*) tmp_string.ptr(),
+                                        tmp_string.alloced_length(),
+                                        "%4d-%02d-%02d %02d:%02d:%02d",
+                                        next_activation_at.year,
+                                        next_activation_at.month,
+                                        next_activation_at.day,
+                                        next_activation_at.hour,
+                                        next_activation_at.minute,
+                                        next_activation_at.second
+                                        ));
+  protocol->store(&tmp_string);
+  ret= protocol->write();
+
 #endif
   DBUG_RETURN(FALSE);
 }

sql/event_queue.h

@@ -36,7 +36,7 @@ class Event_queue
   deinit_mutexes();
 
   bool
-  init_queue(THD *thd, Event_db_repository *db_repo, Event_scheduler *sched);
+  init_queue(THD *thd, Event_db_repository *db_repo);
   
   void
   deinit_queue();
@@ -60,8 +60,7 @@ class Event_queue
   recalculate_activation_times(THD *thd);
 
   bool
-  get_top_for_execution_if_time(THD *thd, time_t now, Event_job_data **job_data,
-                                struct timespec *abstime);
+  get_top_for_execution_if_time(THD *thd, Event_job_data **job_data);
   bool
   dump_internal_status(THD *thd);
 
@@ -80,14 +79,12 @@ class Event_queue
   void
   empty_queue();
 
-  void
-  notify_observers();
-
   void
   dbug_dump_queue(time_t now);
 
   /* LOCK_event_queue is the mutex which protects the access to the queue. */
   pthread_mutex_t LOCK_event_queue;
+  pthread_cond_t COND_queue_state;
 
   Event_db_repository *db_repository;
 
@@ -96,6 +93,8 @@ class Event_queue
   /* The sorted queue with the Event_job_data objects */
   QUEUE queue;
 
+  TIME next_activation_at;
+
   uint mutex_last_locked_at_line;
   uint mutex_last_unlocked_at_line;
   uint mutex_last_attempted_lock_at_line;
@@ -104,6 +103,7 @@ class Event_queue
   const char* mutex_last_attempted_lock_in_func;
   bool mutex_queue_data_locked;
   bool mutex_queue_data_attempting_lock;
+  bool waiting_on_cond;
 
   /* helper functions for working with mutexes & conditionals */
   void
@@ -111,6 +111,10 @@ class Event_queue
 
   void
   unlock_data(const char *func, uint line);
+
+  void
+  cond_wait(THD *thd, struct timespec *abstime, const char* msg,
+            const char *func, uint line);
 };
 
 #endif /* _EVENT_QUEUE_H_ */

sql/event_scheduler.cc

@@ -313,7 +313,7 @@ Event_scheduler::init_scheduler(Event_queue *q)
   LOCK_DATA();
   queue= q;
   started_events= 0;
-  thread_id= 0;
+  scheduler_thd= NULL;
   state= INITIALIZED;
   UNLOCK_DATA();
 }
@@ -397,22 +397,18 @@ Event_scheduler::start()
   scheduler_param_value->thd= new_thd;
   scheduler_param_value->scheduler= this;
 
+  scheduler_thd= new_thd;
+  DBUG_PRINT("info", ("Setting state go RUNNING"));
+  state= RUNNING;
   DBUG_PRINT("info", ("Forking new thread for scheduduler. THD=0x%lx", new_thd));
   if (pthread_create(&th, &connection_attrib, event_scheduler_thread,
                     (void*)scheduler_param_value))
   {
     DBUG_PRINT("error", ("cannot create a new thread"));
     state= INITIALIZED;
+    scheduler_thd= NULL;
     ret= TRUE;
-  }
-  DBUG_PRINT("info", ("Setting state go RUNNING"));
-  state= RUNNING;
-end:
-  UNLOCK_DATA();
 
-  if (ret && new_thd)
-  {
-    DBUG_PRINT("info", ("There was an error during THD creation. Clean up"));
     new_thd->proc_info= "Clearing";
     DBUG_ASSERT(new_thd->net.buff != 0);
     net_end(&new_thd->net);
@@ -422,6 +418,9 @@ Event_scheduler::start()
     delete new_thd;
     pthread_mutex_unlock(&LOCK_thread_count);
   }
+end:
+  UNLOCK_DATA();
+
   DBUG_RETURN(ret);
 }
 
@@ -446,66 +445,41 @@ Event_scheduler::run(THD *thd)
   Event_job_data *job_data;
   DBUG_ENTER("Event_scheduler::run");
 
-  LOCK_DATA();
-
-  thread_id= thd->thread_id;
   sql_print_information("SCHEDULER: Manager thread started with id %lu",
-                        thread_id);
+                        thd->thread_id);
   /*
     Recalculate the values in the queue because there could have been stops
     in executions of the scheduler and some times could have passed by.
   */
   queue->recalculate_activation_times(thd);
-  while (state == RUNNING)
+
+  while (is_running())
   {
-    thd->end_time();
     /* Gets a minimized version */
-    if (queue->get_top_for_execution_if_time(thd, thd->query_start(),
-                                             &job_data, &abstime))
+    if (queue->get_top_for_execution_if_time(thd, &job_data))
     {
-      sql_print_information("SCHEDULER: Serious error during getting next"
-                            " event to execute. Stopping");
+      sql_print_information("SCHEDULER: Serious error during getting next "
+                            "event to execute. Stopping");
       break;
     }
 
-    DBUG_PRINT("info", ("get_top returned job_data=0x%lx now=%d "
-                        "abs_time.tv_sec=%d",
-                        job_data, thd->query_start(), abstime.tv_sec));
-    if (!job_data && !abstime.tv_sec)
-    {
-      DBUG_PRINT("info", ("The queue is empty. Going to sleep"));
-      COND_STATE_WAIT(thd, NULL, "Waiting on empty queue");
-      DBUG_PRINT("info", ("Woke up. Got COND_state"));
-    }
-    else if (abstime.tv_sec)
+    DBUG_PRINT("info", ("get_top returned job_data=0x%lx", job_data));
+    if (job_data)
     {
-      DBUG_PRINT("info", ("Have to sleep some time %u s. till %u",
-                 abstime.tv_sec - thd->query_start(), abstime.tv_sec));
-
-      COND_STATE_WAIT(thd, &abstime, "Waiting for next activation");
-      /*
-        If we get signal we should recalculate the whether it's the right time
-        because there could be :
-        1. Spurious wake-up
-        2. The top of the queue was changed (new one becase of create/update)
-      */
-      DBUG_PRINT("info", ("Woke up. Got COND_stat or time for execution."));
+      if ((res= execute_top(thd, job_data)))
+        break;
     }
     else
     {
-      UNLOCK_DATA();
-      res= execute_top(thd, job_data);
-      LOCK_DATA();
-      if (res)
-        break;
-      ++started_events;
+      DBUG_ASSERT(thd->killed);
+      DBUG_PRINT("info", ("job_data is NULL, the thread was killed"));
     }
     DBUG_PRINT("info", ("state=%s", scheduler_states_names[state].str));
   }
+  LOCK_DATA();
   DBUG_PRINT("info", ("Signalling back to the stopper COND_state"));
-  pthread_cond_signal(&COND_state);
-error:
   state= INITIALIZED;
+  pthread_cond_signal(&COND_state);
   UNLOCK_DATA();
   sql_print_information("SCHEDULER: Stopped");
 
@@ -546,6 +520,8 @@ Event_scheduler::execute_top(THD *thd, Event_job_data *job_data)
                            job_data)))
     goto error;
 
+  ++started_events;
+
   DBUG_PRINT("info", ("Launch succeeded. BURAN is in THD=0x%lx", new_thd));
   DBUG_RETURN(FALSE);
 
@@ -567,6 +543,27 @@ Event_scheduler::execute_top(THD *thd, Event_job_data *job_data)
 }
 
 
+/*
+  Checkes whether the state of the scheduler is RUNNING
+
+  SYNOPSIS
+    Event_scheduler::is_running()
+
+  RETURN VALUE
+    TRUE   RUNNING
+    FALSE  Not RUNNING
+*/
+
+inline bool
+Event_scheduler::is_running()
+{
+  LOCK_DATA();
+  bool ret= (state == RUNNING);
+  UNLOCK_DATA();
+  return ret;
+}
+
+
 /*
   Stops the scheduler (again). Waits for acknowledgement from the
   scheduler that it has stopped - synchronous stopping.
@@ -591,26 +588,48 @@ Event_scheduler::stop()
   if (state != RUNNING)
     goto end;
 
-  state= STOPPING;
-
-  DBUG_PRINT("info", ("Manager thread has id %d", thread_id));
-  sql_print_information("SCHEDULER: Killing manager thread %lu", thread_id);
-  
-  pthread_cond_signal(&COND_state);
-
   /* Guarantee we don't catch spurious signals */
-  sql_print_information("SCHEDULER: Waiting the manager thread to reply");
   do {
     DBUG_PRINT("info", ("Waiting for COND_started_or_stopped from the manager "
                         "thread.  Current value of state is %s . "
                         "workers count=%d", scheduler_states_names[state].str,
                         workers_count()));
+    /*
+      NOTE: We don't use kill_one_thread() because it can't kill COM_DEAMON
+      threads. In addition, kill_one_thread() requires THD but during shutdown
+      current_thd is NULL. Hence, if kill_one_thread should be used it has to
+      be modified to kill also daemons, by adding a flag, and also we have to
+      create artificial THD here. To save all this work, we just do what
+      kill_one_thread() does to kill a thread. See also sql_repl.cc for similar
+      usage.
+    */
+
+    state= STOPPING;
+    DBUG_PRINT("info", ("Manager thread has id %d", scheduler_thd->thread_id));
+    /* Lock from delete */
+    pthread_mutex_lock(&scheduler_thd->LOCK_delete);
+    /* This will wake up the thread if it waits on Queue's conditional */
+    sql_print_information("SCHEDULER: Killing manager thread %lu",
+                          scheduler_thd->thread_id);
+    scheduler_thd->awake(THD::KILL_CONNECTION);
+    pthread_mutex_unlock(&scheduler_thd->LOCK_delete);
+
     /* thd could be 0x0, when shutting down */
+    sql_print_information("SCHEDULER: Waiting the manager thread to reply");
     COND_STATE_WAIT(thd, NULL, "Waiting scheduler to stop");
   } while (state == STOPPING);
   DBUG_PRINT("info", ("Manager thread has cleaned up. Set state to INIT"));
-
-  thread_id= 0;
+  /*
+    The rationale behind setting it to NULL here but not destructing it
+    beforehand is because the THD will be deinited in event_scheduler_thread().
+    It's more clear when the post_init and the deinit is done in one function.
+    Here we just mark that the scheduler doesn't have a THD anymore. Though for
+    milliseconds the old thread could exist we can't use it anymore. When we
+    unlock the mutex in this function a little later the state will be
+    INITIALIZED. Therefore, a connection thread could enter the critical section
+    and will create a new THD object.
+  */
+  scheduler_thd= NULL;
 end:
   UNLOCK_DATA();
   DBUG_RETURN(FALSE);
@@ -634,37 +653,14 @@ Event_scheduler::workers_count()
   pthread_mutex_lock(&LOCK_thread_count);       // For unlink from list
   I_List_iterator<THD> it(threads);
   while ((tmp=it++))
-  {
-    if (tmp->command == COM_DAEMON)
-      continue;
     if (tmp->system_thread == SYSTEM_THREAD_EVENT_WORKER)
       ++count;
-  }
   pthread_mutex_unlock(&LOCK_thread_count);
   DBUG_PRINT("exit", ("%d", count));
   DBUG_RETURN(count);
 }
 
 
-/*
-  Signals the main scheduler thread that the queue has changed
-  its state.
-
-  SYNOPSIS
-    Event_scheduler::queue_changed()
-*/
-
-void
-Event_scheduler::queue_changed()
-{
-  DBUG_ENTER("Event_scheduler::queue_changed");
-  DBUG_PRINT("info", ("Sending COND_state. state (read wo lock)=%s ",
-             scheduler_states_names[state].str));
-  pthread_cond_signal(&COND_state);
-  DBUG_VOID_RETURN;
-}
-
-
 /*
   Auxiliary function for locking LOCK_scheduler_state. Used
   by the LOCK_DATA macro.
@@ -718,6 +714,7 @@ Event_scheduler::unlock_data(const char *func, uint line)
     Event_scheduler::cond_wait()
       thd     Thread (Could be NULL during shutdown procedure)
       abstime If not null then call pthread_cond_timedwait()
+      msg     Message for thd->proc_info
       func    Which function is requesting cond_wait
       line    On which line cond_wait is requested
 */
@@ -756,33 +753,6 @@ Event_scheduler::cond_wait(THD *thd, struct timespec *abstime, const char* msg,
 }
 
 
-/*
-  Returns the current state of the scheduler
-
-  SYNOPSIS
-    Event_scheduler::get_state()
-
-  RETURN VALUE
-    The state of the scheduler (INITIALIZED | RUNNING | STOPPING)
-*/
-
-enum Event_scheduler::enum_state
-Event_scheduler::get_state()
-{
-  enum Event_scheduler::enum_state ret;
-  DBUG_ENTER("Event_scheduler::get_state");
-  LOCK_DATA();
-  ret= state;
-  UNLOCK_DATA();
-  DBUG_RETURN(ret);
-}
-
-
-/*
-  REMOVE THIS COMMENT AFTER PATCH REVIEW. USED TO HELP DIFF
-  Returns whether the scheduler was initialized.
-*/
-
 /*
   Dumps the internal status of the scheduler
 
@@ -826,7 +796,7 @@ Event_scheduler::dump_internal_status(THD *thd)
     protocol->store(STRING_WITH_LEN("thread_id"), scs);
     if (thread_id)
     {
-      int_string.set((longlong) thread_id, scs);
+      int_string.set((longlong) scheduler_thd->thread_id, scs);
       protocol->store(&int_string);
     }
     else

sql/event_scheduler.h

@@ -34,14 +34,6 @@ class Event_scheduler
   Event_scheduler():state(UNINITIALIZED){}
   ~Event_scheduler(){}
 
-  enum enum_state
-  {
-    UNINITIALIZED = 0,
-    INITIALIZED,
-    RUNNING,
-    STOPPING
-  };
-
   /* State changing methods follow */
 
   bool
@@ -70,12 +62,8 @@ class Event_scheduler
   deinit_mutexes();
 
   /* Information retrieving methods follow */
-
-  enum enum_state
-  get_state();
-
-  void
-  queue_changed();
+  bool
+  is_running();
 
   bool
   dump_internal_status(THD *thd);
@@ -84,6 +72,7 @@ class Event_scheduler
   uint
   workers_count();
 
+
   /* helper functions */
   bool
   execute_top(THD *thd, Event_job_data *job_data);
@@ -101,16 +90,18 @@ class Event_scheduler
 
   pthread_mutex_t LOCK_scheduler_state;
 
+  enum enum_state
+  {
+    UNINITIALIZED = 0,
+    INITIALIZED,
+    RUNNING,
+    STOPPING
+  };
+
   /* This is the current status of the life-cycle of the scheduler. */
   enum enum_state state;
 
-  /*
-    Holds the thread id of the executor thread or 0 if the scheduler is not
-    running. It is used by ::shutdown() to know which thread to kill with
-    kill_one_thread(). The latter wake ups a thread if it is waiting on a
-    conditional variable and sets thd->killed to non-zero.
-  */
-  ulong thread_id;
+  THD *scheduler_thd;
 
   pthread_cond_t COND_state;
 

sql/events.cc

@@ -637,7 +637,7 @@ Events::init()
   }
   check_system_tables_error= FALSE;
 
-  if (event_queue->init_queue(thd, db_repository, scheduler))
+  if (event_queue->init_queue(thd, db_repository))
   {
     sql_print_error("SCHEDULER: Error while loading from disk.");
     goto end;
@@ -827,7 +827,7 @@ Events::is_execution_of_events_started()
     my_error(ER_EVENTS_DB_ERROR, MYF(0));
     DBUG_RETURN(FALSE);
   }
-  DBUG_RETURN(scheduler->get_state() == Event_scheduler::RUNNING);
+  DBUG_RETURN(scheduler->is_running());
 }