TTY: ldisc, allow waiting for ldisc arbitrarily long

To fix a nasty bug in ldisc hup vs. reinit we need to wait infinitely
long for ldisc to be gone. So here we add a parameter to
tty_ldisc_wait_idle to allow that.

This is only a preparation for the real fix which is done in the
following patches.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Dave Young <hidave.darkstar@gmail.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: Dmitriy Matrosov <sgf.dma@gmail.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 6 insertions, 5 deletions

diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index 512c49f98e8..534d176a78e 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -547,15 +547,16 @@ static void tty_ldisc_flush_works(struct tty_struct *tty)
 /**
  *      tty_ldisc_wait_idle     -       wait for the ldisc to become idle
  *      @tty: tty to wait for
+ *      @timeout: for how long to wait at most
  *
  *      Wait for the line discipline to become idle. The discipline must
  *      have been halted for this to guarantee it remains idle.
  */
-static int tty_ldisc_wait_idle(struct tty_struct *tty)
+static int tty_ldisc_wait_idle(struct tty_struct *tty, long timeout)
 {
-        int ret;
+        long ret;
         ret = wait_event_timeout(tty_ldisc_idle,
-                        atomic_read(&tty->ldisc->users) == 1, 5 * HZ);
+                        atomic_read(&tty->ldisc->users) == 1, timeout);
         if (ret < 0)
                 return ret;
         return ret > 0 ? 0 : -EBUSY;
@@ -665,7 +666,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
 
         tty_ldisc_flush_works(tty);
 
-        retval = tty_ldisc_wait_idle(tty);
+        retval = tty_ldisc_wait_idle(tty, 5 * HZ);
 
         tty_lock();
         mutex_lock(&tty->ldisc_mutex);
@@ -762,7 +763,7 @@ static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc)
         if (IS_ERR(ld))
                 return -1;
 
-        WARN_ON_ONCE(tty_ldisc_wait_idle(tty));
+        WARN_ON_ONCE(tty_ldisc_wait_idle(tty, 5 * HZ));
 
         tty_ldisc_close(tty, tty->ldisc);
         tty_ldisc_put(tty->ldisc);