From e043e42bdb66885b3ac10d27a01ccb9972e2b0a3 Mon Sep 17 00:00:00 2001 From: OGAWA Hirofumi Date: Wed, 29 Jul 2009 12:15:56 -0700 Subject: pty: avoid forcing 'low_latency' tty flag We really don't want to mark the pty as a low-latency device, because as Alan points out, the ->write method can be called from an IRQ (ppp?), and that means we can't use ->low_latency=1 as we take mutexes in the low_latency case. So rather than using low_latency to force the written data to be pushed to the ldisc handling at 'write()' time, just make the reader side (or the poll function) do the flush when it checks whether there is data to be had. This also fixes the problem with lost data in an emacs compile buffer (bugzilla 13815), and we can thus revert the low_latency pty hack (commit 3a54297478e6578f96fd54bf4daa1751130aca86: "pty: quickfix for the pty ENXIO timing problems"). Signed-off-by: OGAWA Hirofumi Tested-by: Aneesh Kumar K.V [ Modified to do the tty_flush_to_ldisc() inside input_available_p() so that it triggers for both read and poll() - Linus] Signed-off-by: Linus Torvalds --- drivers/char/pty.c | 2 -- 1 file changed, 2 deletions(-) (limited to 'drivers/char/pty.c') diff --git a/drivers/char/pty.c b/drivers/char/pty.c index 3850a68f265a..6e6942c45f5b 100644 --- a/drivers/char/pty.c +++ b/drivers/char/pty.c @@ -52,7 +52,6 @@ static void pty_close(struct tty_struct *tty, struct file *filp) return; tty->link->packet = 0; set_bit(TTY_OTHER_CLOSED, &tty->link->flags); - tty_flip_buffer_push(tty->link); wake_up_interruptible(&tty->link->read_wait); wake_up_interruptible(&tty->link->write_wait); if (tty->driver->subtype == PTY_TYPE_MASTER) { @@ -208,7 +207,6 @@ static int pty_open(struct tty_struct *tty, struct file *filp) clear_bit(TTY_OTHER_CLOSED, &tty->link->flags); set_bit(TTY_THROTTLED, &tty->flags); retval = 0; - tty->low_latency = 1; out: return retval; } -- cgit v1.2.2 From 85dfd81dc57e8183a277ddd7a56aa65c96f3f487 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Mon, 10 Aug 2009 13:21:19 -0700 Subject: pty: fix data loss when stopped (^S/^Q) Commit d945cb9cc ("pty: Rework the pty layer to use the normal buffering logic") dropped the test for 'tty->stopped' in pty_write_room(), which then causes the n_tty line discipline thing to not throttle the data properly when the tty is stopped. So instead of pausing the write due to the tty being stopped, the ldisc layer would go ahead and push it down to the pty. The pty write() routine would then refuse to take the data (because it _did_ check 'stopped'), and the data wouldn't actually be written. This whole stopped test should eventually be moved into the tty ldisc layer rather than have low-level tty drivers care about these things, but right now the fix is to just re-instate the missing pty 'stopped' handling. Reported-and-tested-by: Artur Skawina Cc: Alan Cox Signed-off-by: Linus Torvalds --- drivers/char/pty.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/char/pty.c') diff --git a/drivers/char/pty.c b/drivers/char/pty.c index 6e6942c45f5b..d083c73d784a 100644 --- a/drivers/char/pty.c +++ b/drivers/char/pty.c @@ -144,6 +144,8 @@ static int pty_write(struct tty_struct *tty, const unsigned char *buf, static int pty_write_room(struct tty_struct *tty) { + if (tty->stopped) + return 0; return pty_space(tty->link); } -- cgit v1.2.2