Change connection_count back to static

Code structual change only, just limiting
super global variables especially when the
counter under the THD structure should be used
in general.

sql/mysqld.cc

@@ -1466,7 +1466,7 @@ struct st_VioSSLFd *ssl_acceptor_fd;
 /**
   Number of currently active user connections.
 */
-Atomic_counter<uint> connection_count;
+static Atomic_counter<uint> connection_count;
 static Atomic_counter<uint> extra_connection_count;
 
 my_bool opt_gtid_strict_mode= FALSE;
@@ -8571,15 +8571,20 @@ static int get_options(int *argc_ptr, char ***argv_ptr)
     return 1;
 
 #ifdef EMBEDDED_LIBRARY
-  one_thread_scheduler(thread_scheduler);
-  one_thread_scheduler(extra_thread_scheduler);
+  one_thread_scheduler(thread_scheduler, &connection_count);
+  /*
+    It looks like extra_connection_count should be passed here but
+    its been using connection_count for the last 10+ years and
+    no-one was requested a change so lets not suprise anyone.
+  */
+  one_thread_scheduler(extra_thread_scheduler, &connection_count);
 #else
 
   if (thread_handling <= SCHEDULER_ONE_THREAD_PER_CONNECTION)
     one_thread_per_connection_scheduler(thread_scheduler, &max_connections,
                                         &connection_count);
   else if (thread_handling == SCHEDULER_NO_THREADS)
-    one_thread_scheduler(thread_scheduler);
+    one_thread_scheduler(thread_scheduler, &connection_count);
   else
     pool_of_threads_scheduler(thread_scheduler,  &max_connections,
                                         &connection_count); 

sql/mysqld.h

@@ -116,7 +116,6 @@ extern bool opt_ignore_builtin_innodb;
 extern my_bool opt_character_set_client_handshake;
 extern my_bool debug_assert_on_not_freed_memory;
 extern MYSQL_PLUGIN_IMPORT bool volatile abort_loop;
-extern Atomic_counter<uint> connection_count;
 extern my_bool opt_safe_user_create;
 extern my_bool opt_safe_show_db, opt_local_infile, opt_myisam_use_mmap;
 extern my_bool opt_slave_compressed_protocol, use_temp_pool;

sql/scheduler.cc

@@ -131,11 +131,12 @@ void handle_connection_in_main_thread(CONNECT *connect)
   Initialize scheduler for --thread-handling=no-threads
 */
 
-void one_thread_scheduler(scheduler_functions *func)
+void one_thread_scheduler(scheduler_functions *func,
+    Atomic_counter<uint> *arg_connection_count)
 {
   scheduler_init();
   func->max_threads= 1;
   func->max_connections= &max_connections;
-  func->connection_count= &connection_count;
+  func->connection_count= arg_connection_count;
   func->add_connection= handle_connection_in_main_thread;
 }

sql/scheduler.h

@@ -74,7 +74,7 @@ enum scheduler_types
 
 void one_thread_per_connection_scheduler(scheduler_functions *func,
     ulong *arg_max_connections, Atomic_counter<uint> *arg_connection_count);
-void one_thread_scheduler(scheduler_functions *func);
+void one_thread_scheduler(scheduler_functions *func, Atomic_counter<uint> *arg_connection_count);
 
 extern void scheduler_init();
 extern void post_kill_notification(THD *);