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path: root/drivers/char/tty_ldisc.c
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Diffstat (limited to 'drivers/char/tty_ldisc.c')
-rw-r--r--drivers/char/tty_ldisc.c43
1 files changed, 30 insertions, 13 deletions
diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c
index 500e740..412f977 100644
--- a/drivers/char/tty_ldisc.c
+++ b/drivers/char/tty_ldisc.c
@@ -440,6 +440,8 @@ static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
*
* A helper opening method. Also a convenient debugging and check
* point.
+ *
+ * Locking: always called with BTM already held.
*/
static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
@@ -447,10 +449,9 @@ static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags));
if (ld->ops->open) {
int ret;
- /* BKL here locks verus a hangup event */
- lock_kernel();
+ /* BTM here locks versus a hangup event */
+ WARN_ON(!tty_locked());
ret = ld->ops->open(tty);
- unlock_kernel();
return ret;
}
return 0;
@@ -553,7 +554,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
if (IS_ERR(new_ldisc))
return PTR_ERR(new_ldisc);
- lock_kernel();
+ tty_lock();
/*
* We need to look at the tty locking here for pty/tty pairs
* when both sides try to change in parallel.
@@ -567,12 +568,12 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
*/
if (tty->ldisc->ops->num == ldisc) {
- unlock_kernel();
+ tty_unlock();
tty_ldisc_put(new_ldisc);
return 0;
}
- unlock_kernel();
+ tty_unlock();
/*
* Problem: What do we do if this blocks ?
* We could deadlock here
@@ -580,6 +581,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
tty_wait_until_sent(tty, 0);
+ tty_lock();
mutex_lock(&tty->ldisc_mutex);
/*
@@ -589,13 +591,13 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) {
mutex_unlock(&tty->ldisc_mutex);
+ tty_unlock();
wait_event(tty_ldisc_wait,
test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0);
+ tty_lock();
mutex_lock(&tty->ldisc_mutex);
}
- lock_kernel();
-
set_bit(TTY_LDISC_CHANGING, &tty->flags);
/*
@@ -607,7 +609,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
o_ldisc = tty->ldisc;
- unlock_kernel();
+ tty_unlock();
/*
* Make sure we don't change while someone holds a
* reference to the line discipline. The TTY_LDISC bit
@@ -632,15 +634,15 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
flush_scheduled_work();
+ tty_lock();
mutex_lock(&tty->ldisc_mutex);
- lock_kernel();
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);
- unlock_kernel();
+ tty_unlock();
return -EIO;
}
@@ -682,7 +684,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
if (o_work)
schedule_delayed_work(&o_tty->buf.work, 1);
mutex_unlock(&tty->ldisc_mutex);
- unlock_kernel();
+ tty_unlock();
return retval;
}
@@ -780,7 +782,20 @@ void tty_ldisc_hangup(struct tty_struct *tty)
* Avoid racing set_ldisc or tty_ldisc_release
*/
mutex_lock(&tty->ldisc_mutex);
- tty_ldisc_halt(tty);
+
+ /*
+ * this is like tty_ldisc_halt, but we need to give up
+ * the BTM before calling cancel_delayed_work_sync,
+ * which may need to wait for another function taking the BTM
+ */
+ clear_bit(TTY_LDISC, &tty->flags);
+ tty_unlock();
+ cancel_delayed_work_sync(&tty->buf.work);
+ mutex_unlock(&tty->ldisc_mutex);
+
+ tty_lock();
+ mutex_lock(&tty->ldisc_mutex);
+
/* At this point we have a closed ldisc and we want to
reopen it. We could defer this to the next open but
it means auditing a lot of other paths so this is
@@ -851,8 +866,10 @@ void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
* race with the set_ldisc code path.
*/
+ tty_unlock();
tty_ldisc_halt(tty);
flush_scheduled_work();
+ tty_lock();
mutex_lock(&tty->ldisc_mutex);
/*
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