MDEV-34814 mysqld hangs on startup when --init-file target does not e…

…xist

Set select_thread_in_use only when we're about to enter into the polling
loop, not sooner, allowing early proces aborts to exist cleanly: the
process won't be waiting for a polling loop that isn't yet polling.

sql/mysqld.cc

@@ -5344,6 +5344,26 @@ static void test_lc_time_sz()
 #endif//DBUG_OFF
 
 
+static void signal_accept_connections()
+{
+  select_thread=pthread_self();
+  mysql_mutex_lock(&LOCK_start_thread);
+  select_thread_in_use=1;
+  mysql_mutex_unlock(&LOCK_start_thread);
+
+#ifdef _WIN32
+  handle_connections_win();
+#else
+  handle_connections_sockets();
+
+  mysql_mutex_lock(&LOCK_start_thread);
+  select_thread_in_use=0;
+  mysql_cond_broadcast(&COND_start_thread);
+  mysql_mutex_unlock(&LOCK_start_thread);
+#endif /* _WIN32 */
+}
+
+
 #ifdef __WIN__
 int win_main(int argc, char **argv)
 #else
@@ -5540,9 +5560,6 @@ int mysqld_main(int argc, char **argv)
     SYSVAR_AUTOSIZE(my_thread_stack_size, new_thread_stack_size);
   }
 
-  select_thread=pthread_self();
-  select_thread_in_use=1;
-
 #ifdef HAVE_LIBWRAP
   libwrapName= my_progname+dirname_length(my_progname);
   openlog(libwrapName, LOG_PID, LOG_AUTH);
@@ -5596,7 +5613,6 @@ int mysqld_main(int argc, char **argv)
   // Recover and exit.
   if (wsrep_recovery)
   {
-    select_thread_in_use= 0;
     if (WSREP_ON)
       wsrep_recover();
     else
@@ -5671,7 +5687,6 @@ int mysqld_main(int argc, char **argv)
 
   if (opt_bootstrap)
   {
-    select_thread_in_use= 0;                    // Allow 'kill' to work
     int bootstrap_error= bootstrap(mysql_stdin);
     if (!abort_loop)
       unireg_abort(bootstrap_error);
@@ -5751,16 +5766,7 @@ int mysqld_main(int argc, char **argv)
   /* Memory used when everything is setup */
   start_memory_used= global_status_var.global_memory_used;
 
-#ifdef _WIN32
-  handle_connections_win();
-#else
-  handle_connections_sockets();
-
-  mysql_mutex_lock(&LOCK_start_thread);
-  select_thread_in_use=0;
-  mysql_cond_broadcast(&COND_start_thread);
-  mysql_mutex_unlock(&LOCK_start_thread);
-#endif /* _WIN32 */
+  signal_accept_connections();
 
   /* Shutdown requested */
   char *user= shutdown_user.load(std::memory_order_relaxed);