fd:
	#tell kernel the iop should be executed on context switch
	iop_valid
	#iop data
	write_io_page

fprintf params
	lock write_mutex
	fd->iop_valid=0

	if !fd->write_io_page
		fd->write_io_page=io_page_alloc
	
	print_stuff_to fd->write_io_page params
	if buffer full
		flush
		printf_continue params printf_state

	fd->iop_valid=1

	unlock write_mutex