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Groups > linux.kernel > #1305477

[PATCH v2 7/7] tty: n_tty: fix SIGIO for output

From Peter Hurley <peter@hurleysoftware.com>
Newsgroups linux.kernel
Subject [PATCH v2 7/7] tty: n_tty: fix SIGIO for output
Date 2016-01-10 06:50 +0100
Message-ID <qPh34-8nj-21@gated-at.bofh.it> (permalink)
References <qF0Gd-8bC-3@gated-at.bofh.it> <qPh33-8nj-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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According to fcntl(2), "a SIGIO signal is sent whenever input
or output becomes possible on that file descriptor", i.e.
after the output buffer was full and now has space for new data.
But in fact SIGIO is sent after every write.

n_tty_write() should set TTY_DO_WRITE_WAKEUP only when
not all data could be written to the buffer.

[pjh: Also fixes missed SIGIO if amt written just happens to be
[     amount still to write

Signed-off-by: Johannes Stezenbach <js@sig21.net>
[pjh: minor patch edits and re-submit]

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
 drivers/tty/n_tty.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 5ae661c..fad365a 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -2361,7 +2361,7 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
 	}
 break_out:
 	remove_wait_queue(&tty->write_wait, &wait);
-	if (b - buf != nr && tty->fasync)
+	if (nr && tty->fasync)
 		set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 	up_read(&tty->termios_rwsem);
 	return (b - buf) ? b - buf : retval;
-- 
2.7.0

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Thread

[PATCH v2 0/7] More n_tty fixes Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:50 +0100
  [PATCH v2 2/7] tty, n_tty: Remove fasync() ldisc notification Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:50 +0100
  [PATCH v2 5/7] n_tty: Fix stuck write wakeup Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:50 +0100
  [PATCH v2 3/7] tty: Add fasync() hung up file operation Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:50 +0100
  [PATCH v2 6/7] n_tty: Remove tty count checks from unthrottle Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:50 +0100
  [PATCH v2 4/7] tty: Fix ioctl(FIOASYNC) on hungup file Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:50 +0100
  [PATCH v2 7/7] tty: n_tty: fix SIGIO for output Peter Hurley <peter@hurleysoftware.com> - 2016-01-10 06:50 +0100

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