Bug#28510721 TSAN: DATA RACE IN EVENT_QUEUE::LOCK_DATA

Fix data race in Event_queue::Lock_data() by making
Event_queue::mutex_last_attempted_lock_at_line
             mutex_last_attempted_lock_in_func
             mutex_queue_data_attempting_lock
atomic variables.

The contents of these variables are printed by the SIGHUP
signal handler and by COM_DEBUG if the events scheduler is
active. Note that since these variables are updated separately,
it is still not guaranteed that they together form a consistent
state.

Change-Id: Ie7719ab78eceb3a6afb0cdd2e959aaccc4a7c1b3

Author: jhauglid

sql/event_queue.cc

@@ -769,8 +769,9 @@ void Event_queue::dump_internal_status() {
   printf("LUA             : %s:%u\n", mutex_last_unlocked_in_func,
          mutex_last_unlocked_at_line);
   if (mutex_last_attempted_lock_at_line)
-    printf("Last lock attempt at: %s:%u\n", mutex_last_attempted_lock_in_func,
-           mutex_last_attempted_lock_at_line);
+    printf("Last lock attempt at: %s:%u\n",
+           mutex_last_attempted_lock_in_func.load(),
+           mutex_last_attempted_lock_at_line.load());
   printf("WOC             : %s\n", waiting_on_cond ? "YES" : "NO");
 
   MYSQL_TIME time;

sql/event_queue.h

@@ -1,6 +1,6 @@
 #ifndef _EVENT_QUEUE_H_
 #define _EVENT_QUEUE_H_
-/* Copyright (c) 2004, 2017, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2004, 2018, 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, version 2.0,
@@ -34,6 +34,7 @@
 
 #include <sys/types.h>
 #include <time.h>
+#include <atomic>
 #include <vector>
 
 #include "lex_string.h"
@@ -157,12 +158,12 @@ class Event_queue {
 
   uint mutex_last_locked_at_line;
   uint mutex_last_unlocked_at_line;
-  uint mutex_last_attempted_lock_at_line;
+  std::atomic<uint> mutex_last_attempted_lock_at_line;
   const char *mutex_last_locked_in_func;
   const char *mutex_last_unlocked_in_func;
-  const char *mutex_last_attempted_lock_in_func;
+  std::atomic<const char *> mutex_last_attempted_lock_in_func;
   bool mutex_queue_data_locked;
-  bool mutex_queue_data_attempting_lock;
+  std::atomic<bool> mutex_queue_data_attempting_lock;
   bool waiting_on_cond;
 };
 /**