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path: root/drivers/tty/tty_ldisc.c
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Diffstat (limited to 'drivers/tty/tty_ldisc.c')
-rw-r--r--drivers/tty/tty_ldisc.c46
1 files changed, 32 insertions, 14 deletions
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index e4603b09863a..2fe216b276e2 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -492,6 +492,29 @@ static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld)
}
/**
+ * tty_ldisc_failto - helper for ldisc failback
+ * @tty: tty to open the ldisc on
+ * @ld: ldisc we are trying to fail back to
+ *
+ * Helper to try and recover a tty when switching back to the old
+ * ldisc fails and we need something attached.
+ */
+
+static int tty_ldisc_failto(struct tty_struct *tty, int ld)
+{
+ struct tty_ldisc *disc = tty_ldisc_get(tty, ld);
+ int r;
+
+ if (IS_ERR(disc))
+ return PTR_ERR(disc);
+ tty->ldisc = disc;
+ tty_set_termios_ldisc(tty, ld);
+ if ((r = tty_ldisc_open(tty, disc)) < 0)
+ tty_ldisc_put(disc);
+ return r;
+}
+
+/**
* tty_ldisc_restore - helper for tty ldisc change
* @tty: tty to recover
* @old: previous ldisc
@@ -502,9 +525,6 @@ static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld)
static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old)
{
- struct tty_ldisc *new_ldisc;
- int r;
-
/* There is an outstanding reference here so this is safe */
old = tty_ldisc_get(tty, old->ops->num);
WARN_ON(IS_ERR(old));
@@ -512,17 +532,13 @@ static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *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(tty, N_TTY);
- if (IS_ERR(new_ldisc))
- panic("n_tty: get");
- tty->ldisc = 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), r);
+ /* The traditional behaviour is to fall back to N_TTY, we
+ want to avoid falling back to N_NULL unless we have no
+ choice to avoid the risk of breaking anything */
+ if (tty_ldisc_failto(tty, N_TTY) < 0 &&
+ tty_ldisc_failto(tty, N_NULL) < 0)
+ panic("Couldn't open N_NULL ldisc for %s.",
+ tty_name(tty));
}
}
@@ -605,6 +621,7 @@ err:
tty_unlock(tty);
return retval;
}
+EXPORT_SYMBOL_GPL(tty_set_ldisc);
/**
* tty_ldisc_kill - teardown ldisc
@@ -797,6 +814,7 @@ void tty_ldisc_release(struct tty_struct *tty)
tty_ldisc_debug(tty, "released\n");
}
+EXPORT_SYMBOL_GPL(tty_ldisc_release);
/**
* tty_ldisc_init - ldisc setup for new tty