tty: Revert the tty locking series, it needs more work
This reverts the tty layer change to use per-tty locking, because it's
not correct yet, and fixing it will require some more deep surgery.
The main revert is d29f3ef39be4 ("tty_lock: Localise the lock"), but
there are several smaller commits that built upon it, they also get
reverted here. The list of reverted commits is:
fde86d310886 - tty: add lockdep annotations
8f6576ad476b - tty: fix ldisc lock inversion trace
d3ca8b64b97e - pty: Fix lock inversion
b1d679afd766 - tty: drop the pty lock during hangup
abcefe5fc357 - tty/amiserial: Add missing argument for tty_unlock()
fd11b42e3598 - cris: fix missing tty arg in wait_event_interruptible_tty call
d29f3ef39be4 - tty_lock: Localise the lock
The revert had a trivial conflict in the 68360serial.c staging driver
that got removed in the meantime.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index ba8be39..9911eb6 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -568,7 +568,7 @@
if (IS_ERR(new_ldisc))
return PTR_ERR(new_ldisc);
- tty_lock(tty);
+ tty_lock();
/*
* We need to look at the tty locking here for pty/tty pairs
* when both sides try to change in parallel.
@@ -582,12 +582,12 @@
*/
if (tty->ldisc->ops->num == ldisc) {
- tty_unlock(tty);
+ tty_unlock();
tty_ldisc_put(new_ldisc);
return 0;
}
- tty_unlock(tty);
+ tty_unlock();
/*
* Problem: What do we do if this blocks ?
* We could deadlock here
@@ -595,7 +595,7 @@
tty_wait_until_sent(tty, 0);
- tty_lock(tty);
+ tty_lock();
mutex_lock(&tty->ldisc_mutex);
/*
@@ -605,10 +605,10 @@
while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) {
mutex_unlock(&tty->ldisc_mutex);
- tty_unlock(tty);
+ tty_unlock();
wait_event(tty_ldisc_wait,
test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0);
- tty_lock(tty);
+ tty_lock();
mutex_lock(&tty->ldisc_mutex);
}
@@ -623,7 +623,7 @@
o_ldisc = tty->ldisc;
- tty_unlock(tty);
+ tty_unlock();
/*
* Make sure we don't change while someone holds a
* reference to the line discipline. The TTY_LDISC bit
@@ -650,7 +650,7 @@
retval = tty_ldisc_wait_idle(tty, 5 * HZ);
- tty_lock(tty);
+ tty_lock();
mutex_lock(&tty->ldisc_mutex);
/* handle wait idle failure locked */
@@ -665,7 +665,7 @@
clear_bit(TTY_LDISC_CHANGING, &tty->flags);
mutex_unlock(&tty->ldisc_mutex);
tty_ldisc_put(new_ldisc);
- tty_unlock(tty);
+ tty_unlock();
return -EIO;
}
@@ -708,7 +708,7 @@
if (o_work)
schedule_work(&o_tty->buf.work);
mutex_unlock(&tty->ldisc_mutex);
- tty_unlock(tty);
+ tty_unlock();
return retval;
}
@@ -816,11 +816,11 @@
* need to wait for another function taking the BTM
*/
clear_bit(TTY_LDISC, &tty->flags);
- tty_unlock(tty);
+ tty_unlock();
cancel_work_sync(&tty->buf.work);
mutex_unlock(&tty->ldisc_mutex);
retry:
- tty_lock(tty);
+ tty_lock();
mutex_lock(&tty->ldisc_mutex);
/* At this point we have a closed ldisc and we want to
@@ -831,7 +831,7 @@
if (atomic_read(&tty->ldisc->users) != 1) {
char cur_n[TASK_COMM_LEN], tty_n[64];
long timeout = 3 * HZ;
- tty_unlock(tty);
+ tty_unlock();
while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) {
timeout = MAX_SCHEDULE_TIMEOUT;
@@ -894,23 +894,6 @@
tty_ldisc_enable(tty);
return 0;
}
-
-static void tty_ldisc_kill(struct tty_struct *tty)
-{
- mutex_lock(&tty->ldisc_mutex);
- /*
- * Now kill off the ldisc
- */
- tty_ldisc_close(tty, tty->ldisc);
- tty_ldisc_put(tty->ldisc);
- /* Force an oops if we mess this up */
- tty->ldisc = NULL;
-
- /* Ensure the next open requests the N_TTY ldisc */
- tty_set_termios_ldisc(tty, N_TTY);
- mutex_unlock(&tty->ldisc_mutex);
-}
-
/**
* tty_ldisc_release - release line discipline
* @tty: tty being shut down
@@ -929,19 +912,27 @@
* race with the set_ldisc code path.
*/
- tty_unlock_pair(tty, o_tty);
+ tty_unlock();
tty_ldisc_halt(tty);
tty_ldisc_flush_works(tty);
- if (o_tty) {
- tty_ldisc_halt(o_tty);
- tty_ldisc_flush_works(o_tty);
- }
- tty_lock_pair(tty, o_tty);
+ tty_lock();
+ mutex_lock(&tty->ldisc_mutex);
+ /*
+ * Now kill off the ldisc
+ */
+ tty_ldisc_close(tty, tty->ldisc);
+ tty_ldisc_put(tty->ldisc);
+ /* Force an oops if we mess this up */
+ tty->ldisc = NULL;
- tty_ldisc_kill(tty);
+ /* Ensure the next open requests the N_TTY ldisc */
+ tty_set_termios_ldisc(tty, N_TTY);
+ mutex_unlock(&tty->ldisc_mutex);
+
+ /* This will need doing differently if we need to lock */
if (o_tty)
- tty_ldisc_kill(o_tty);
+ tty_ldisc_release(o_tty, NULL);
/* And the memory resources remaining (buffers, termios) will be
disposed of when the kref hits zero */