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Subject[23/53] TTY: ldisc, allow waiting for ldisc arbitrarily long
3.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jiri Slaby <jslaby@suse.cz>

commit df92d0561de364de53c42abc5d43e04ab6f326a5 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/tty/tty_ldisc.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)

--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -548,15 +548,16 @@ static void tty_ldisc_flush_works(struct
/**
* 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;
@@ -666,7 +667,7 @@ int tty_set_ldisc(struct tty_struct *tty

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);
@@ -763,7 +764,7 @@ static int tty_ldisc_reinit(struct tty_s
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);



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