Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[sfrench/cifs-2.6.git] / drivers / tty / tty_ldisc.c

diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index fc4c97cae01ef4812da9b1bf61d6efe5d9cf6784..45eda69b150c4a48292a625d3409bb3ef293cdc7 100644 (file)
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -327,6 +327,11 @@ int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout)
 {
        int ret;
 
+       /* Kindly asking blocked readers to release the read side */
+       set_bit(TTY_LDISC_CHANGING, &tty->flags);
+       wake_up_interruptible_all(&tty->read_wait);
+       wake_up_interruptible_all(&tty->write_wait);
+
        ret = __tty_ldisc_lock(tty, timeout);
        if (!ret)
                return -EBUSY;
@@ -337,6 +342,8 @@ int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout)
 void tty_ldisc_unlock(struct tty_struct *tty)
 {
        clear_bit(TTY_LDISC_HALTED, &tty->flags);
+       /* Can be cleared here - ldisc_unlock will wake up writers firstly */
+       clear_bit(TTY_LDISC_CHANGING, &tty->flags);
        __tty_ldisc_unlock(tty);
 }
 
@@ -471,6 +478,7 @@ static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
 
 static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld)
 {
+       lockdep_assert_held_exclusive(&tty->ldisc_sem);
        WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags));
        clear_bit(TTY_LDISC_OPEN, &tty->flags);
        if (ld->ops->close)
@@ -492,6 +500,7 @@ static int tty_ldisc_failto(struct tty_struct *tty, int ld)
        struct tty_ldisc *disc = tty_ldisc_get(tty, ld);
        int r;
 
+       lockdep_assert_held_exclusive(&tty->ldisc_sem);
        if (IS_ERR(disc))
                return PTR_ERR(disc);
        tty->ldisc = disc;
@@ -615,6 +624,7 @@ EXPORT_SYMBOL_GPL(tty_set_ldisc);
  */
 static void tty_ldisc_kill(struct tty_struct *tty)
 {
+       lockdep_assert_held_exclusive(&tty->ldisc_sem);
        if (!tty->ldisc)
                return;
        /*
@@ -662,6 +672,7 @@ int tty_ldisc_reinit(struct tty_struct *tty, int disc)
        struct tty_ldisc *ld;
        int retval;
 
+       lockdep_assert_held_exclusive(&tty->ldisc_sem);
        ld = tty_ldisc_get(tty, disc);
        if (IS_ERR(ld)) {
                BUG_ON(disc == N_TTY);
@@ -760,6 +771,10 @@ int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty)
                return retval;
 
        if (o_tty) {
+               /*
+                * Called without o_tty->ldisc_sem held, as o_tty has been
+                * just allocated and no one has a reference to it.
+                */
                retval = tty_ldisc_open(o_tty, o_tty->ldisc);
                if (retval) {
                        tty_ldisc_close(tty, tty->ldisc);
@@ -825,6 +840,7 @@ int tty_ldisc_init(struct tty_struct *tty)
  */
 void tty_ldisc_deinit(struct tty_struct *tty)
 {
+       /* no ldisc_sem, tty is being destroyed */
        if (tty->ldisc)
                tty_ldisc_put(tty->ldisc);
        tty->ldisc = NULL;