Messages in this thread Patch in this message | | | From | Peter Hurley <> | Subject | Re: Bug in tty cooked mode kernel 3.12.3 | Date | Mon, 9 Dec 2013 18:06:07 -0500 |
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On 12/07/2013 06:46 PM, Karl Dahlke wrote: > This may have appeared in 3.9.11 with the changes to tty. > Don't know; I just started running 3.12 from kernel.org. > Perhaps nobody saw it before because nobody runs command line programs, > we're all on desktops or x or whatever, > and even those in the command line are still raw. > bash is raw by default, but I run it cooked. > You can supress its readline functions like this. > > set +o emacs > set +o vi > set +o histexpand > set +o history > > That puts its tty back into cooked mode. > > Come up in run level 3, command line mode, > and bring up two consoles with bash in cooked mode as above. > Set a simple prompt like this. > > PS1='$ ' > > Switch to console 2 via alt-f2. > Hit return. > The cursor should drop to a new line then give you the $ prompt. > But it puts the $ prompt next too the old one, then drops down > to a blank line. > The $ prompt and the crlf are out of sequence. > Hit return a few more times and it will straighten itself out. > Then switch back to console 1 alt-f1 > Hit return and the same bug, > $ $ > > hit return a few more times to straighten it out. > Switch back to console 2 and the same problem. > For me it's repeatable. > > It's also very confusing when I'm running other command line programs with cooked tty. > For unknown reasons the crlf can come out at the wrong time, > breaking lines or leaving lines together. > My editor can run either way, so I've switched it over to readline mode > and I haven't noticed any problems this way, yet. > But I would prefer the cooked mode. > > I looked through MAINTAINERS but couldn't find > a clear maintainer for drivers/tty/tty*.c > Please forward this to the appropriate people.
Thanks for the report, Karl.
Please test the patch below (requires commit 39434abd942c8e4b9c14c06a03b3245beaf8467f, 'n_tty: Fix missing newline echo'). This should fix the 'newline output after the new prompt' problem.
Note however that the other output order you observe is correct: you press enter, a newline is echoed to terminal which mixes with program output, the program ends, and the cooked mode shell outputs an extra prompt because it reads a newline (which the program did not read).
Regards, Peter Hurley
--- >% --- From: Peter Hurley <peter@hurleysoftware.com> Subject: [PATCH] n_tty: Fix apparent order of echoed output
With block processing of echoed output, observed output order is still required. Push completed echoes and echo commands prior to output.
Introduce echo_mark echo buffer index, which tracks completed echo commands; ie., those submitted via commit_echoes but which may not have been committed. Ensure that completed echoes are output prior to subsequent terminal writes in process_echoes().
Fixes newline/prompt output order in cooked mode shell.
Cc: <stable@vger.kernel.org> # 3.12.x : 39434ab n_tty: Fix missing newline echo Reported-by: Karl Dahlke <eklhad@comcast.net> Reported-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Peter Hurley <peter@hurleysoftware.com> --- drivers/tty/n_tty.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index ab24fe1..e9304b6 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -94,6 +94,7 @@ struct n_tty_data { size_t canon_head; size_t echo_head; size_t echo_commit; + size_t echo_mark; DECLARE_BITMAP(char_map, 256); /* private to n_tty_receive_overrun (single-threaded) */ @@ -339,6 +340,7 @@ static void reset_buffer_flags(struct n_tty_data *ldata) { ldata->read_head = ldata->canon_head = ldata->read_tail = 0; ldata->echo_head = ldata->echo_tail = ldata->echo_commit = 0; + ldata->echo_mark = 0; ldata->line_start = 0; ldata->erasing = 0; @@ -791,6 +793,7 @@ static void commit_echoes(struct tty_struct *tty) size_t head; head = ldata->echo_head; + ldata->echo_mark = head; old = ldata->echo_commit - ldata->echo_tail; /* Process committed echoes if the accumulated # of bytes @@ -815,10 +818,11 @@ static void process_echoes(struct tty_struct *tty) size_t echoed; if ((!L_ECHO(tty) && !L_ECHONL(tty)) || - ldata->echo_commit == ldata->echo_tail) + ldata->echo_mark == ldata->echo_tail) return; mutex_lock(&ldata->output_lock); + ldata->echo_commit = ldata->echo_mark; echoed = __process_echoes(tty); mutex_unlock(&ldata->output_lock); @@ -826,6 +830,7 @@ static void process_echoes(struct tty_struct *tty) tty->ops->flush_chars(tty); } +/* NB: echo_mark and echo_head should be equivalent here */ static void flush_echoes(struct tty_struct *tty) { struct n_tty_data *ldata = tty->disc_data; -- 1.8.1.2
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