Post-fix for MDEV-14587

dict_stats_process_entry_from_defrag_pool(): Release the mutex

storage/innobase/dict/dict0stats_bg.cc

@@ -511,6 +511,7 @@ dict_stats_process_entry_from_defrag_pool()
 		return;
 	}
 
+	mutex_exit(&dict_sys->mutex);
 	dict_stats_save_defrag_stats(index);
 	dict_table_close(table, FALSE, FALSE);
 }

storage/xtradb/dict/dict0stats_bg.cc

@@ -512,6 +512,7 @@ dict_stats_process_entry_from_defrag_pool()
 		return;
 	}
 
+	mutex_exit(&dict_sys->mutex);
 	dict_stats_save_defrag_stats(index);
 	dict_table_close(table, FALSE, FALSE);
 }