diff options
| author | Peter Hurley <peter@hurleysoftware.com> | 2016-01-10 22:41:01 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-01-27 15:01:44 -0800 |
| commit | e55afd11a48354c810caf6b6ad4c103016a88230 (patch) | |
| tree | eb073c28c1e21785fcbe92740ce1290da7fcb85c /drivers/tty/tty_ldisc.c | |
| 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>
Diffstat (limited to 'drivers/tty/tty_ldisc.c')
| -rw-r--r-- | drivers/tty/tty_ldisc.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c index 14d2165ba270..d6805e1aee59 100644 --- a/drivers/tty/tty_ldisc.c +++ b/drivers/tty/tty_ldisc.c @@ -262,8 +262,8 @@ const struct file_operations tty_ldiscs_proc_fops = { * against a discipline change, such as an existing ldisc reference * (which we check for) * - * Note: only callable from a file_operations routine (which - * guarantees tty->ldisc != NULL when the lock is acquired). + * Note: a file_operations routine (read/poll/write) should use this + * function to wait for any ldisc lifetime events to finish. */ struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) |