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tty: n_tty: fix SIGIO for output 

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley 2016-01-09 21:45:14 -08:00 committed by Greg Kroah-Hartman
parent ffb91a459c
commit 87108bc987
1 changed files with 1 additions and 1 deletions
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2
drivers/tty/n_tty.c
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@ -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;