| commit | e55afd11a48354c810caf6b6ad4c103016a88230 | [log] [tgz] |
|---|---|---|
| author | Peter Hurley <peter@hurleysoftware.com> | Sun Jan 10 22:41:01 2016 -0800 |
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | Wed Jan 27 15:01:44 2016 -0800 |
| tree | eb073c28c1e21785fcbe92740ce1290da7fcb85c | |
| parent | 5b6e6832f41c9422753804671ee06af37ac8caf6 [diff] |
tty: Prepare for destroying line discipline on hangup
tty file_operations (read/write/ioctl) wait for the ldisc reference
indefinitely (until ldisc lifetime events, such as hangup or TIOCSETD,
finish). Since hangup now destroys the ldisc and does not instance
another copy, file_operations must now be prepared to receive a NULL
ldisc reference from tty_ldisc_ref_wait():
CPU 0 CPU 1
----- -----
(*f_op->read)() => tty_read()
__tty_hangup()
...
f_op = &hung_up_tty_fops;
...
tty_ldisc_hangup()
tty_ldisc_lock()
tty_ldisc_kill()
tty->ldisc = NULL
tty_ldisc_unlock()
ld = tty_ldisc_ref_wait()
/* ld == NULL */
Instead, the action taken now is to return the same value as if the
tty had been hungup a moment earlier:
CPU 0 CPU 1
----- -----
__tty_hangup()
...
f_op = &hung_up_tty_fops;
(*f_op->read)() => hung_up_tty_read()
return 0;
...
tty_ldisc_hangup()
tty_ldisc_lock()
tty_ldisc_kill()
tty->ldisc = NULL
tty_ldisc_unlock()
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>