On Sat, Jun 15, 2013 at 10:04:20AM -0400, Peter Hurley wrote: > ** v2 changes ** > - Rebased on v2 of 'lockless tty flip buffers' > > This 3rd of 4 patchsets implements a mostly-lockless tty echo output. > > Because echoing is performed solely by the single-threaded ldisc > receive_buf() method, most of the lockless requirements are already > in-place. The main existing complications were; > 1) Echoing could overrun itself. A fixed-size buffer is used to record > the operations necessary when outputting the echoes; the most recent > echo data is preserved. > 2) An attempt to push unprocessed echoes is made by the n_tty_write method > (on a different thread) before attempting write output. > > The overrun condition is solved by outputting the echoes in blocks and > ensuring that at least that much space is available each time an echo > operation is committed. At the conclusion of each flip buffer received, > any remaining unprocessed echoes are output. > > This block output method is particularly effective when there is no reader > (the tty is output-only) and termios is misconfigured with echo enabled. > > The concurrent access by the n_tty_write() method is already excluded > by the existing output_lock mutex. Applied, thanks. greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
