[PATCH 1/1] TTY: ldisc, don't wait with ldisc_mutex

[Jiri Slaby]

Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 drivers/tty/tty_ldisc.c |   16 +++++++++++++---
 1 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index 24b95db..c93e113 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -527,6 +527,14 @@ static void tty_ldisc_flush_works(struct tty_struct *tty)
 	flush_work_sync(&tty->buf.work);
 }
 
+static bool tty_ldisc_is_idle(struct tty_struct *tty)
+{
+	bool idle;
+	mutex_lock(&tty->ldisc_mutex);
+	idle = !tty->ldisc || atomic_read(&tty->ldisc->users) == 1;
+	mutex_unlock(&tty->ldisc_mutex);
+	return idle;
+}
 /**
  *	tty_ldisc_wait_idle	-	wait for the ldisc to become idle
  *	@tty: tty to wait for
@@ -534,12 +542,14 @@ static void tty_ldisc_flush_works(struct tty_struct *tty)
  *
  *	Wait for the line discipline to become idle. The discipline must
  *	have been halted for this to guarantee it remains idle.
+ *
+ *	Locking: neither BTM, nor tty->ldisc_mutex must be held
  */
 static int tty_ldisc_wait_idle(struct tty_struct *tty, long timeout)
 {
 	long ret;
-	ret = wait_event_timeout(tty_ldisc_idle,
-			atomic_read(&tty->ldisc->users) == 1, timeout);
+	ret = wait_event_timeout(tty_ldisc_idle, tty_ldisc_is_idle(tty),
+			timeout);
 	return ret > 0 ? 0 : -EBUSY;
 }
 
@@ -830,6 +840,7 @@ retry:
 		if (atomic_read(&tty->ldisc->users) != 1) {
 			char cur_n[TASK_COMM_LEN], tty_n[64];
 			long timeout = 3 * HZ;
+			mutex_unlock(&tty->ldisc_mutex);
 			tty_unlock();
 
 			while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) {
@@ -839,7 +850,6 @@ retry:
 					__func__, get_task_comm(cur_n, current),
 					tty_name(tty, tty_n));
 			}
-			mutex_unlock(&tty->ldisc_mutex);
 			goto retry;
 		}
 
-- 
1.7.7.3


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