static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old)
{
char buf[64];
struct tty_ldisc new_ldisc;
/* There is an outstanding reference here so this is safe */
tty_ldisc_get(old->ops->num, old);
tty_ldisc_assign(tty, old);
tty_set_termios_ldisc(tty, old->ops->num);
if (old->ops->open && (old->ops->open(tty) < 0)) {
tty_ldisc_put(old->ops);
/* This driver is always present */
if (tty_ldisc_get(N_TTY, &new_ldisc) < 0)
panic("n_tty: get");
tty_ldisc_assign(tty, &new_ldisc);
tty_set_termios_ldisc(tty, N_TTY);
if (new_ldisc.ops->open) {
int r = new_ldisc.ops->open(tty);
if (r < 0)
panic("Couldn't open N_TTY ldisc for "
"%s --- error %d.",
tty_name(tty, buf), r);
}
}
}
static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old)
{
char buf[64];
struct tty_ldisc *new_ldisc;
int r;
/* There is an outstanding reference here so this is safe */
old = tty_ldisc_get(old->ops->num);
WARN_ON(IS_ERR(old));
tty_ldisc_assign(tty, old);
tty_set_termios_ldisc(tty, old->ops->num);
if (tty_ldisc_open(tty, old) < 0) {
tty_ldisc_put(old);
/* This driver is always present */
new_ldisc = tty_ldisc_get(N_TTY);
if (IS_ERR(new_ldisc))
panic("n_tty: get");
tty_ldisc_assign(tty, new_ldisc);
tty_set_termios_ldisc(tty, N_TTY);
r = tty_ldisc_open(tty, new_ldisc);
if (r < 0)
panic("Couldn't open N_TTY ldisc for "
"%s --- error %d.",
tty_name(tty, buf), r);
}
}
void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
{
unsigned long flags;
struct tty_ldisc ld;
/*
* Prevent flush_to_ldisc() from rescheduling the work for later. Then
* kill any delayed work. As this is the final close it does not
* race with the set_ldisc code path.
*/
clear_bit(TTY_LDISC, &tty->flags);
cancel_delayed_work(&tty->buf.work);
/*
* Wait for ->hangup_work and ->buf.work handlers to terminate
*/
flush_scheduled_work();
/*
* Wait for any short term users (we know they are just driver
* side waiters as the file is closing so user count on the file
* side is zero.
*/
spin_lock_irqsave(&tty_ldisc_lock, flags);
while (tty->ldisc.refcount) {
spin_unlock_irqrestore(&tty_ldisc_lock, flags);
wait_event(tty_ldisc_wait, tty->ldisc.refcount == 0);
spin_lock_irqsave(&tty_ldisc_lock, flags);
}
spin_unlock_irqrestore(&tty_ldisc_lock, flags);
/*
* Shutdown the current line discipline, and reset it to N_TTY.
*
* FIXME: this MUST get fixed for the new reflocking
*/
if (tty->ldisc.ops->close)
(tty->ldisc.ops->close)(tty);
tty_ldisc_put(tty->ldisc.ops);
/*
* Switch the line discipline back
*/
WARN_ON(tty_ldisc_get(N_TTY, &ld));
tty_ldisc_assign(tty, &ld);
tty_set_termios_ldisc(tty, N_TTY);
if (o_tty) {
/* FIXME: could o_tty be in setldisc here ? */
clear_bit(TTY_LDISC, &o_tty->flags);
if (o_tty->ldisc.ops->close)
(o_tty->ldisc.ops->close)(o_tty);
tty_ldisc_put(o_tty->ldisc.ops);
WARN_ON(tty_ldisc_get(N_TTY, &ld));
tty_ldisc_assign(o_tty, &ld);
tty_set_termios_ldisc(o_tty, N_TTY);
}
}
void tty_ldisc_init(struct tty_struct *tty)
{
struct tty_ldisc ld;
if (tty_ldisc_get(N_TTY, &ld) < 0)
panic("n_tty: init_tty");
tty_ldisc_assign(tty, &ld);
}
void tty_ldisc_init(struct tty_struct *tty)
{
struct tty_ldisc *ld = tty_ldisc_get(N_TTY);
if (IS_ERR(ld))
panic("n_tty: init_tty");
tty_ldisc_assign(tty, ld);
}
static void tty_ldisc_reinit(struct tty_struct *tty)
{
struct tty_ldisc *ld;
tty_ldisc_close(tty, tty->ldisc);
tty_ldisc_put(tty->ldisc);
tty->ldisc = NULL;
/*
* Switch the line discipline back
*/
ld = tty_ldisc_get(N_TTY);
BUG_ON(IS_ERR(ld));
tty_ldisc_assign(tty, ld);
tty_set_termios_ldisc(tty, N_TTY);
}
static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc)
{
struct tty_ldisc *ld = tty_ldisc_get(ldisc);
if (IS_ERR(ld))
return -1;
tty_ldisc_close(tty, tty->ldisc);
tty_ldisc_put(tty->ldisc);
tty->ldisc = NULL;
/*
* Switch the line discipline back
*/
tty_ldisc_assign(tty, ld);
tty_set_termios_ldisc(tty, ldisc);
return 0;
}
static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc) #else //static void tty_ldisc_reinit(struct tty_struct *tty, int ldisc) #endif //20110402 [email protected] [LS855] handle exception for tty daemon [END] { //20110402 [email protected] [LS855] handle exception for tty daemon [START] #if 1 struct tty_ldisc *ld = tty_ldisc_get(ldisc); #else // struct tty_ldisc *ld; #endif //20110402 [email protected] [LS855] handle exception for tty daemon [END] if (IS_ERR(ld)) return -1; tty_ldisc_close(tty, tty->ldisc); tty_ldisc_put(tty->ldisc); tty->ldisc = NULL; /* * Switch the line discipline back */ //20110402 [email protected] [LS855] handle exception for tty daemon [START] #if 0 ld = tty_ldisc_get(ldisc); BUG_ON(IS_ERR(ld)); #endif //20110402 [email protected] [LS855] handle exception for tty daemon [END] tty_ldisc_assign(tty, ld); tty_set_termios_ldisc(tty, ldisc); return 0; //20110402 [email protected] [LS855] handle exception for tty daemon }
int tty_set_ldisc(struct tty_struct *tty, int ldisc)
{
int retval;
struct tty_ldisc o_ldisc, new_ldisc;
int work;
unsigned long flags;
struct tty_struct *o_tty;
restart:
/* This is a bit ugly for now but means we can break the 'ldisc
is part of the tty struct' assumption later */
retval = tty_ldisc_get(ldisc, &new_ldisc);
if (retval)
return retval;
/*
* Problem: What do we do if this blocks ?
*/
tty_wait_until_sent(tty, 0);
if (tty->ldisc.ops->num == ldisc) {
tty_ldisc_put(new_ldisc.ops);
return 0;
}
/*
* No more input please, we are switching. The new ldisc
* will update this value in the ldisc open function
*/
tty->receive_room = 0;
o_ldisc = tty->ldisc;
o_tty = tty->link;
/*
* Make sure we don't change while someone holds a
* reference to the line discipline. The TTY_LDISC bit
* prevents anyone taking a reference once it is clear.
* We need the lock to avoid racing reference takers.
*
* We must clear the TTY_LDISC bit here to avoid a livelock
* with a userspace app continually trying to use the tty in
* parallel to the change and re-referencing the tty.
*/
clear_bit(TTY_LDISC, &tty->flags);
if (o_tty)
clear_bit(TTY_LDISC, &o_tty->flags);
spin_lock_irqsave(&tty_ldisc_lock, flags);
if (tty->ldisc.refcount || (o_tty && o_tty->ldisc.refcount)) {
if (tty->ldisc.refcount) {
/* Free the new ldisc we grabbed. Must drop the lock
first. */
spin_unlock_irqrestore(&tty_ldisc_lock, flags);
tty_ldisc_put(new_ldisc.ops);
/*
* There are several reasons we may be busy, including
* random momentary I/O traffic. We must therefore
* retry. We could distinguish between blocking ops
* and retries if we made tty_ldisc_wait() smarter.
* That is up for discussion.
*/
if (wait_event_interruptible(tty_ldisc_wait, tty->ldisc.refcount == 0) < 0)
return -ERESTARTSYS;
goto restart;
}
if (o_tty && o_tty->ldisc.refcount) {
spin_unlock_irqrestore(&tty_ldisc_lock, flags);
tty_ldisc_put(o_tty->ldisc.ops);
if (wait_event_interruptible(tty_ldisc_wait, o_tty->ldisc.refcount == 0) < 0)
return -ERESTARTSYS;
goto restart;
}
}
/*
* If the TTY_LDISC bit is set, then we are racing against
* another ldisc change
*/
if (test_bit(TTY_LDISC_CHANGING, &tty->flags)) {
struct tty_ldisc *ld;
spin_unlock_irqrestore(&tty_ldisc_lock, flags);
tty_ldisc_put(new_ldisc.ops);
ld = tty_ldisc_ref_wait(tty);
tty_ldisc_deref(ld);
goto restart;
}
/*
* This flag is used to avoid two parallel ldisc changes. Once
* open and close are fine grained locked this may work better
* as a mutex shared with the open/close/hup paths
*/
set_bit(TTY_LDISC_CHANGING, &tty->flags);
if (o_tty)
set_bit(TTY_LDISC_CHANGING, &o_tty->flags);
spin_unlock_irqrestore(&tty_ldisc_lock, flags);
/*
* From this point on we know nobody has an ldisc
* usage reference, nor can they obtain one until
* we say so later on.
*/
work = cancel_delayed_work(&tty->buf.work);
/*
* Wait for ->hangup_work and ->buf.work handlers to terminate
* MUST NOT hold locks here.
*/
flush_scheduled_work();
/* Shutdown the current discipline. */
if (o_ldisc.ops->close)
(o_ldisc.ops->close)(tty);
/* Now set up the new line discipline. */
tty_ldisc_assign(tty, &new_ldisc);
tty_set_termios_ldisc(tty, ldisc);
if (new_ldisc.ops->open)
retval = (new_ldisc.ops->open)(tty);
if (retval < 0) {
tty_ldisc_put(new_ldisc.ops);
tty_ldisc_restore(tty, &o_ldisc);
}
/* At this point we hold a reference to the new ldisc and a
a reference to the old ldisc. If we ended up flipping back
to the existing ldisc we have two references to it */
if (tty->ldisc.ops->num != o_ldisc.ops->num && tty->ops->set_ldisc)
tty->ops->set_ldisc(tty);
tty_ldisc_put(o_ldisc.ops);
/*
* Allow ldisc referencing to occur as soon as the driver
* ldisc callback completes.
*/
tty_ldisc_enable(tty);
if (o_tty)
tty_ldisc_enable(o_tty);
/* Restart it in case no characters kick it off. Safe if
already running */
if (work)
schedule_delayed_work(&tty->buf.work, 1);
return retval;
}
int tty_set_ldisc(struct tty_struct *tty, int ldisc)
{
int retval;
struct tty_ldisc *o_ldisc, *new_ldisc;
int work, o_work = 0;
struct tty_struct *o_tty;
new_ldisc = tty_ldisc_get(ldisc);
if (IS_ERR(new_ldisc))
return PTR_ERR(new_ldisc);
/*
* We need to look at the tty locking here for pty/tty pairs
* when both sides try to change in parallel.
*/
o_tty = tty->link; /* o_tty is the pty side or NULL */
/*
* Check the no-op case
*/
if (tty->ldisc->ops->num == ldisc) {
tty_ldisc_put(new_ldisc);
return 0;
}
/*
* Problem: What do we do if this blocks ?
* We could deadlock here
*/
tty_wait_until_sent(tty, 0);
mutex_lock(&tty->ldisc_mutex);
/*
* We could be midstream of another ldisc change which has
* dropped the lock during processing. If so we need to wait.
*/
while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) {
mutex_unlock(&tty->ldisc_mutex);
wait_event(tty_ldisc_wait,
test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0);
mutex_lock(&tty->ldisc_mutex);
}
set_bit(TTY_LDISC_CHANGING, &tty->flags);
/*
* No more input please, we are switching. The new ldisc
* will update this value in the ldisc open function
*/
tty->receive_room = 0;
o_ldisc = tty->ldisc;
/*
* Make sure we don't change while someone holds a
* reference to the line discipline. The TTY_LDISC bit
* prevents anyone taking a reference once it is clear.
* We need the lock to avoid racing reference takers.
*
* We must clear the TTY_LDISC bit here to avoid a livelock
* with a userspace app continually trying to use the tty in
* parallel to the change and re-referencing the tty.
*/
work = tty_ldisc_halt(tty);
if (o_tty)
o_work = tty_ldisc_halt(o_tty);
/*
* Wait for ->hangup_work and ->buf.work handlers to terminate.
* We must drop the mutex here in case a hangup is also in process.
*/
mutex_unlock(&tty->ldisc_mutex);
flush_scheduled_work();
mutex_lock(&tty->ldisc_mutex);
if (test_bit(TTY_HUPPED, &tty->flags)) {
/* We were raced by the hangup method. It will have stomped
the ldisc data and closed the ldisc down */
clear_bit(TTY_LDISC_CHANGING, &tty->flags);
mutex_unlock(&tty->ldisc_mutex);
tty_ldisc_put(new_ldisc);
return -EIO;
}
/* Shutdown the current discipline. */
tty_ldisc_close(tty, o_ldisc);
/* Now set up the new line discipline. */
tty_ldisc_assign(tty, new_ldisc);
tty_set_termios_ldisc(tty, ldisc);
retval = tty_ldisc_open(tty, new_ldisc);
if (retval < 0) {
/* Back to the old one or N_TTY if we can't */
tty_ldisc_put(new_ldisc);
tty_ldisc_restore(tty, o_ldisc);
}
/* At this point we hold a reference to the new ldisc and a
a reference to the old ldisc. If we ended up flipping back
to the existing ldisc we have two references to it */
if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc)
tty->ops->set_ldisc(tty);
tty_ldisc_put(o_ldisc);
/*
* Allow ldisc referencing to occur again
*/
tty_ldisc_enable(tty);
if (o_tty)
tty_ldisc_enable(o_tty);
/* Restart the work queue in case no characters kick it off. Safe if
already running */
if (work)
schedule_delayed_work(&tty->buf.work, 1);
if (o_work)
schedule_delayed_work(&o_tty->buf.work, 1);
mutex_unlock(&tty->ldisc_mutex);
return retval;
}
/**
* tty_ldisc_init - ldisc cleanup for new tty
* @tty: tty that was allocated recently
*
* The tty structure must not becompletely set up (tty_ldisc_setup) when
* this call is made.
*/
void tty_ldisc_deinit(struct tty_struct *tty)
{
put_ldisc(tty->ldisc);
tty_ldisc_assign(tty, NULL);
}