Hi Peter, On Wed, Jun 10, 2015 at 10:11 AM, Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> wrote: > Well, I still couldn't repro this bug but I have a hypothesis that > the bash sig handler is executing before the flush occurs, perhaps > because the flush is stalled waiting for the write lock. > > Would you please try the patch below? I just wanted to get back to you to say I've been testing your patch for a few weeks and with the patch applied I have never reproduced the problem with Ctrl+C truncating the output (while I've been able to consistently reproduce it without the patch.) I tested it on top of 4.0.4, 4.0.5, 4.1-rc6, 4.1-rc8, 4.1, 4.1.y and 4.2-rc1. Do you think you could send this patch for inclusion in kernel 4.2? Feel free to include: Reported-by: Filipe Brandenburger <filbranden@xxxxxxxxxx> Tested-by: Filipe Brandenburger <filbranden@xxxxxxxxxx> Acked-by: Filipe Brandenburger <filbranden@xxxxxxxxxx> (whichever ones you find more appropriate) Ideally also a reference to the Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=99351 And possibly one to this mail thread: http://www.spinics.net/lists/linux-serial/msg17791.html BTW, perhaps this also belongs in stable kernels 4.0.y and 4.1.y, if you feel that's appropriate perhaps forward it to stable when you push it upstream. Cheers! Filipe > --- >% --- > Subject: [PATCH] n_tty: signal and flush atomically > > When handling signalling char, claim the termios write lock before > signalling waiting readers and writers to prevent further i/o > before flushing the echo and output buffers. This prevents a > userspace signal handler which may output from racing the terminal > flush. > > Reference: Bugzilla #99351 ("Output truncated in ssh session after...") > Fixes: commit d2b6f44779d3 ("n_tty: Fix signal handling flushes") > Reported-by: Filipe Brandenburger <filbranden@xxxxxxxxxx> > Signed-off-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> > --- > drivers/tty/n_tty.c | 16 +++++++++++++--- > 1 file changed, 13 insertions(+), 3 deletions(-) > > diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c > index c9c27f6..ee8bfac 100644 > --- a/drivers/tty/n_tty.c > +++ b/drivers/tty/n_tty.c > @@ -1108,19 +1108,29 @@ static void eraser(unsigned char c, struct tty_struct *tty) > * Locking: ctrl_lock > */ > > -static void isig(int sig, struct tty_struct *tty) > +static void __isig(int sig, struct tty_struct *tty) > { > - struct n_tty_data *ldata = tty->disc_data; > struct pid *tty_pgrp = tty_get_pgrp(tty); > if (tty_pgrp) { > kill_pgrp(tty_pgrp, sig, 1); > put_pid(tty_pgrp); > } > +} > > - if (!L_NOFLSH(tty)) { > +static void isig(int sig, struct tty_struct *tty) > +{ > + struct n_tty_data *ldata = tty->disc_data; > + > + if (L_NOFLSH(tty)) { > + /* signal only */ > + __isig(sig, tty); > + > + } else { /* signal and flush */ > up_read(&tty->termios_rwsem); > down_write(&tty->termios_rwsem); > > + __isig(sig, tty); > + > /* clear echo buffer */ > mutex_lock(&ldata->output_lock); > ldata->echo_head = ldata->echo_tail = 0; > -- > 2.4.3 -- 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
