Messages in this thread Patch in this message |  | | | Date | Tue, 28 Jul 2009 17:10:47 -0700 (PDT) | | From | Linus Torvalds <> | | Subject | Re: [PATCH] kdesu broken |
On Wed, 29 Jul 2009, Alan Cox wrote: > > BTW: The tty->low_latency fix doesn't work, because the ->write method > can be called from an IRQ and that means we can't use ->low_latency=1 as > we take mutexes.
Ok. So the end result is that Ogawa-san's fix is the right one. Then we can revert the low_latency=1 thing for pty's entirely. No?
And this is also the one that _looks_ the sanest - ie we do it on the read side, where it matters, rather than on the write side or the flush side (where the proper flushing can _also_ fix the problem, but where it's much more problematic, and where it's a lot less direct about what we care about).
This is just Ogawa's patch, redone against current -git, and with commit 3a54297478e6578f96fd54bf4daa1751130aca86 reverted (Ogawa's patch already undid the non-low_latency part of it).
Now, I wonder if some _other_ line discipline might want to do that same tty_flush_to_ldisc thing in their "do I have data" logic, but I didn't look any closer.
So does this work for everyone? I haven't tested it yet myself, but this is the patch that "looks" right.
Linus
--- drivers/char/n_tty.c | 1 + drivers/char/pty.c | 2 -- drivers/char/tty_buffer.c | 13 +++++++++++++ include/linux/tty.h | 1 + 4 files changed, 15 insertions(+), 2 deletions(-) diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c index ff47907..973be2f 100644 --- a/drivers/char/n_tty.c +++ b/drivers/char/n_tty.c @@ -1583,6 +1583,7 @@ static int n_tty_open(struct tty_struct *tty) static inline int input_available_p(struct tty_struct *tty, int amt) { + tty_flush_to_ldisc(tty); if (tty->icanon) { if (tty->canon_data) return 1; diff --git a/drivers/char/pty.c b/drivers/char/pty.c index 3850a68..6e6942c 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; } diff --git a/drivers/char/tty_buffer.c b/drivers/char/tty_buffer.c index 810ee25..3108991 100644 --- a/drivers/char/tty_buffer.c +++ b/drivers/char/tty_buffer.c @@ -462,6 +462,19 @@ static void flush_to_ldisc(struct work_struct *work) } /** + * tty_flush_to_ldisc + * @tty: tty to push + * + * Push the terminal flip buffers to the line discipline. + * + * Must not be called from IRQ context. + */ +void tty_flush_to_ldisc(struct tty_struct *tty) +{ + flush_to_ldisc(&tty->buf.work.work); +} + +/** * tty_flip_buffer_push - terminal * @tty: tty to push * diff --git a/include/linux/tty.h b/include/linux/tty.h index 1488d8c..e8c6c91 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -394,6 +394,7 @@ extern void __do_SAK(struct tty_struct *tty); extern void disassociate_ctty(int priv); extern void no_tty(void); extern void tty_flip_buffer_push(struct tty_struct *tty); +extern void tty_flush_to_ldisc(struct tty_struct *tty); extern void tty_buffer_free_all(struct tty_struct *tty); extern void tty_buffer_flush(struct tty_struct *tty); extern void tty_buffer_init(struct tty_struct *tty);
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