When tty_buffer_flush calling had been enabled in pty_flush_buffer (in commit 1d1d14da12e79a6c05fbe1a975401f0f56c93316 "pty: Fix buffer flush deadlock"), this causes a issue had been hidden before it.
Don't flush line discipline of another side, because user could see the data in line discipline through poll, TIOCINQ or FIONREAD already. Current behavior break the expection of userspace application in below situations. Example1: Thread A Thread B -------- -------- n_tty_poll return POLLIN CTRL-C trigger pty_flush_buffer tty_buffer_flush n_tty_flush_buffer TIOCINQ or FIONREAD return zero number of bytes Example2: Thread A Thread B -------- -------- TIOCINQ or FIONREAD return valid number of bytes CTRL-C trigger pty_flush_buffer tty_buffer_flush n_tty_flush_buffer n_tty_read still block due to no data I meet this problem(Example1) in konsole, current behavior cause konsole to hangup forever. It has high possibility to trigger the trouble I meet to execute below commands a few times in konsole, because konsole treat current kernel behavior as EOF: 1:cat BigFile 2:CTRL-C Fixes: 1d1d14da12e7 ("pty: Fix buffer flush deadlock") CC: sta...@vger.kernel.org # v4.0+ Signed-off-by: Wang YanQing <udkni...@gmail.com> --- Changes: v1-v2: 1: Rewrite the oneline description, subject. 2: Reword changelog. drivers/tty/pty.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c index a23fa5e..2b90738 100644 --- a/drivers/tty/pty.c +++ b/drivers/tty/pty.c @@ -216,16 +216,11 @@ static int pty_signal(struct tty_struct *tty, int sig) static void pty_flush_buffer(struct tty_struct *tty) { struct tty_struct *to = tty->link; - struct tty_ldisc *ld; if (!to) return; - ld = tty_ldisc_ref(to); - tty_buffer_flush(to, ld); - if (ld) - tty_ldisc_deref(ld); - + tty_buffer_flush(to, NULL); if (to->packet) { spin_lock_irq(&tty->ctrl_lock); tty->ctrl_status |= TIOCPKT_FLUSHWRITE; -- 1.8.5.6.2.g3d8a54e.dirty