fix for bug #17619 Scheduler race conditions

- Scheduler is either initialized at server start or never.
  Starting & stopping is now suspending & resuming.
- The scheduler has clear OO interface
- Now all calls to the scheduler are synchronous
- GLOBAL event_scheduler uses thd::sys_var_tmp (see set_var.cc)
- External API is encapsulated into class Events
- Includes fixes for all comments of Kostja's review of 19.05.2005

Starting to merge into 5.1-release (5.1.10) and push


BitKeeper/etc/ignore:
  Added libmysqld/event_scheduler.cc to the ignore list
libmysqld/Makefile.am:
  executor -> scheduler
mysql-test/r/events.result:
  update result
mysql-test/r/events_bugs.result:
  update result
mysql-test/r/events_logs_tests.result:
  update result
mysql-test/r/events_microsec.result:
  update result
mysql-test/r/events_scheduling.result:
  update result
mysql-test/r/events_stress.result:
  update result
mysql-test/t/disabled.def:
  enable these tests
mysql-test/t/events.test:
  optimize the test a bit for speed, save some seconds runtime
  remove FULL from SHOW EVENTS
  mostly use I_S.EVENTS
mysql-test/t/events_bugs.test:
  Skip irrelevant for the current design tests - all events are loaded
  on server startup. Change in mysql.event will be visible on next server start.
  Don't use numeric error codes.
mysql-test/t/events_logs_tests.test:
  optimize the test a bit for speed
mysql-test/t/events_microsec.test:
   Skip irrelevant for the current design tests - all events are loaded
      on server startup. Change in mysql.event will be visible on next server start.
      Don't use numeric error codes.
mysql-test/t/events_scheduling.test:
  broader test
mysql-test/t/events_stress.test:
  Rework the test to the new architecture of suspending/resuming.
  Use less events, no need for thousands, hundreds is still ok.
sql/Makefile.am:
  executor -> scheduler
sql/cmakelists.txt:
  executor -> scheduler
sql/event.cc:
  - remove todo comments
  - remove unneded evex_queue abstraction functions
  - move events_init() and events_shutdown() from event_executor.cc to here
  - export db_create_event
  - remove evex_load_and_compile_event, part of class Event_scheduler
  - integrate the public interface found in event.h and used by sql_parse.cc
    to use the new class Event_scheduler.
sql/event.h:
  - add COND_finished so if one thread kills a running event it waits on this
  - export callback event_timed_definer_equal, event_timed_identifier_equal(),
    event_timed_name_equal and event_timed_db_equal()
    to be used by Event_scheduler::drop_matching_events()
  - cleanup event.h
  - encapsulated all external interface into class Events
sql/event_executor.cc:
  make it empty, will delete after that
sql/event_priv.h:
  - more things in the private header
  - remove event queue abstraction functions. tightly bind to QUEUE
  - export privately db_drop_event, db_find_event, db_create_event()
  - made change_security_context() and restore_security_context() free functions
sql/event_timed.cc:
  - fix calculation of time when ENDS is set (STARTS is always set)
  - during Event_timed::compile() set the right Security_ctx. Prevents a crash
        during Event_scheduler::load_events_from_db()
  - add Event_timed::kill_thread()
  - implement event_timed_*_equal()
  - made change_security_context() and restore_security_context() free functions.
  - Comments cleanups
sql/lex.h:
  new word scheduler for SHOW SCHEDULER STATUS (available only debug builds)
sql/log.cc:
  move these from event_scheduler.cc
sql/mysql_priv.h:
  refactor kill_one_thread
  export sql_print_message_func and sql_print_message_handlers
sql/mysqld.cc:
  In close_connections, called by kill_server() skip the main scheduler
  thread and use events_shutdown() for shutting down the scheduler, in the same
  manner it's done for RPL.
  Add a new value to --event-scheduler :
  0 <- No scheduler available
  1 <- Start with scheduler enabled
  2 <- Start with scheduler suspended
sql/repl_failsafe.cc:
  refactor thd::system_thread to be an enum
sql/set_var.cc:
  move sys_var_event_executor::update() to set_var.cc
  executor -> scheduler
  use thd::sys_var_tmp
sql/set_var.h:
  executor -> scheduler
sql/share/errmsg.txt:
  3 new error messages
sql/sql_class.cc:
  refactor thd::system_thread to be an enum . more type-safety
sql/sql_class.h:
  refactor thd::system_thread to be an enum . more type-safety
sql/sql_db.cc:
  get the error from evex_drop_schema_events
sql/sql_error.h:
  export warning_level_names
sql/sql_lex.h:
  new command SHOW SCHEDULER STATUS, available only in debug build and
  for debug purposes.
sql/sql_parse.cc:
  refactor kill_one_thread() -> does the *dirty* work, and sql_kill
  just the reporting.
  add handler for SQLCOM_SHOW_SCHEDULER_STATUS
sql/sql_show.cc:
  fix verbosity handling (this will be obsoleted anyway by the fix for 17394).
sql/sql_yacc.yy:
  remove FULL from SHOW EVENTS
  add SHOW SCHEDULER STATUS in debug builds
sql/table.cc:
  Fix valgrind warning.

1 files changed, 67 insertions, 5 deletions

diff --git a/sql/set_var.cc b/sql/set_var.cc
index ae380bdf2d5..9b06e0f833f 100644
--- a/sql/set_var.cc
+++ b/sql/set_var.cc
@@ -56,6 +56,8 @@
 #include <thr_alarm.h>
 #include <myisam.h>
 
+#include "event_scheduler.h"
+
 /* WITH_BERKELEY_STORAGE_ENGINE */
 extern bool berkeley_shared_data;
 extern ulong berkeley_max_lock, berkeley_log_buffer_size;
@@ -106,7 +108,6 @@ extern ulong ndb_report_thresh_binlog_mem_usage;
 
 
 
-extern my_bool event_executor_running_global_var;
 
 static HASH system_variable_hash;
 const char *bool_type_names[]= { "OFF", "ON", NullS };
@@ -222,9 +223,8 @@ sys_var_long_ptr	sys_delayed_insert_timeout("delayed_insert_timeout",
 						   &delayed_insert_timeout);
 sys_var_long_ptr	sys_delayed_queue_size("delayed_queue_size",
 					       &delayed_queue_size);
-sys_var_event_executor  sys_event_executor("event_scheduler",
-					   (my_bool *)
-					   &event_executor_running_global_var);
+
+sys_var_event_scheduler sys_event_scheduler("event_scheduler");
 sys_var_long_ptr	sys_expire_logs_days("expire_logs_days",
 					     &expire_logs_days);
 sys_var_bool_ptr	sys_flush("flush", &myisam_flush);
@@ -747,7 +747,7 @@ SHOW_VAR init_vars[]= {
   {sys_div_precincrement.name,(char*) &sys_div_precincrement,SHOW_SYS},
   {sys_engine_condition_pushdown.name,
    (char*) &sys_engine_condition_pushdown,                          SHOW_SYS},
-  {sys_event_executor.name,   (char*) &sys_event_executor,          SHOW_SYS},
+  {sys_event_scheduler.name,  (char*) &sys_event_scheduler,         SHOW_SYS},
   {sys_expire_logs_days.name, (char*) &sys_expire_logs_days,        SHOW_SYS},
   {sys_flush.name,             (char*) &sys_flush,                  SHOW_SYS},
   {sys_flush_time.name,        (char*) &sys_flush_time,             SHOW_SYS},
@@ -3579,6 +3579,68 @@ byte *sys_var_thd_dbug::value_ptr(THD *thd, enum_var_type type, LEX_STRING *b)
   return (byte*) thd->strdup(buf);
 }
 
+
+/*
+   The update method of the global variable event_scheduler.
+   If event_scheduler is switched from 0 to 1 then the scheduler main
+   thread is resumed and if from 1 to 0 the scheduler thread is suspended
+
+   SYNOPSIS
+     sys_var_event_scheduler::update()
+       thd  Thread context (unused)
+       var  The new value
+
+   Returns
+     FALSE  OK
+     TRUE   Error
+*/
+
+bool
+sys_var_event_scheduler::update(THD *thd, set_var *var)
+{
+  enum Event_scheduler::enum_error_code res;
+  Event_scheduler *scheduler= Event_scheduler::get_instance();
+  /* here start the thread if not running. */
+  DBUG_ENTER("sys_var_event_scheduler::update");
+
+  DBUG_PRINT("new_value", ("%lu", (bool)var->save_result.ulong_value));
+  if (!scheduler->initialized())
+  {
+    my_error(ER_OPTION_PREVENTS_STATEMENT, MYF(0), "--event-scheduler=0");
+    DBUG_RETURN(true);
+  }
+
+  if (var->save_result.ulong_value < 1 || var->save_result.ulong_value > 2)
+  {
+    char buf[64];
+    my_error(ER_WRONG_VALUE_FOR_VAR, MYF(0), "event_scheduler",
+             llstr(var->save_result.ulong_value, buf));
+    DBUG_RETURN(true);
+  }
+  if ((res= scheduler->suspend_or_resume(var->save_result.ulong_value == 1?
+                                         Event_scheduler::RESUME:
+                                         Event_scheduler::SUSPEND)))
+    my_error(ER_EVENT_SET_VAR_ERROR, MYF(0), (uint) res);
+  DBUG_RETURN((bool) res);
+}
+
+
+byte *sys_var_event_scheduler::value_ptr(THD *thd, enum_var_type type,
+                                         LEX_STRING *base)
+{
+  Event_scheduler *scheduler= Event_scheduler::get_instance();
+
+  if (!scheduler->initialized())
+    thd->sys_var_tmp.long_value= 0;
+  else if (scheduler->get_state() == Event_scheduler::RUNNING)
+    thd->sys_var_tmp.long_value= 1;
+  else
+    thd->sys_var_tmp.long_value= 2;
+
+  return (byte*) &thd->sys_var_tmp;
+}
+
+
 /****************************************************************************
   Used templates
 ****************************************************************************/