WL#9556 Writeset-based MTS dependency tracking on master

UBSAN was complaining about a possible “static initialization order
fiasco” between:

in sys_vars.cc:
- static PolyLock_mutex PLock_log(mysql_bin_log.get_log_lock());
in binlog.cc:
- MYSQL_BIN_LOG mysql_bin_log(&sync_binlog_period, WRITE_CACHE);

The fix creates a new PolyLock type to handle only the mysql_bin_log
LOCK_log.

Author: Joao Gramacho

sql/sys_vars.cc

@@ -3618,7 +3618,22 @@ static bool update_binlog_transaction_dependency_tracking(sys_var*, THD*, enum_v
   return false;
 }
 
-static PolyLock_mutex PLock_log(mysql_bin_log.get_log_lock());
+void PolyLock_lock_log::rdlock()
+{
+  mysql_mutex_lock(mysql_bin_log.get_log_lock());
+}
+
+void PolyLock_lock_log::wrlock()
+{
+  mysql_mutex_lock(mysql_bin_log.get_log_lock());
+}
+
+void PolyLock_lock_log::unlock()
+{
+  mysql_mutex_unlock(mysql_bin_log.get_log_lock());
+}
+
+static PolyLock_lock_log PLock_log;
 static const char *opt_binlog_transaction_dependency_tracking_names[]=
        {"COMMIT_ORDER", "WRITESET", "WRITESET_SESSION", NullS};
 static Sys_var_enum Binlog_transaction_dependency_tracking(

sql/sys_vars_shared.h

@@ -67,6 +67,14 @@ class PolyLock_rwlock: public PolyLock
   void unlock() { mysql_rwlock_unlock(rwlock); }
 };
 
+class PolyLock_lock_log: public PolyLock
+{
+public:
+  void rdlock();
+  void wrlock();
+  void unlock();
+};
+
 class AutoWLock
 {
   PolyLock *lock;