1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 6960715c5063..e8c564a53346 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -539,7 +539,6 @@ static void acm_port_down(struct acm *acm)
 {
         int i;
 
-        mutex_lock(&open_mutex);
         if (acm->dev) {
                 usb_autopm_get_interface(acm->control);
                 acm_set_control(acm, acm->ctrlout = 0);
@@ -551,14 +550,15 @@ static void acm_port_down(struct acm *acm)
                 acm->control->needs_remote_wakeup = 0;
                 usb_autopm_put_interface(acm->control);
         }
-        mutex_unlock(&open_mutex);
 }
 
 static void acm_tty_hangup(struct tty_struct *tty)
 {
         struct acm *acm = tty->driver_data;
         tty_port_hangup(&acm->port);
+        mutex_lock(&open_mutex);
         acm_port_down(acm);
+        mutex_unlock(&open_mutex);
 }
 
 static void acm_tty_close(struct tty_struct *tty, struct file *filp)
@@ -569,8 +569,9 @@ static void acm_tty_close(struct tty_struct *tty, struct file *filp)
            shutdown */
         if (!acm)
                 return;
+
+        mutex_lock(&open_mutex);
         if (tty_port_close_start(&acm->port, tty, filp) == 0) {
-                mutex_lock(&open_mutex);
                 if (!acm->dev) {
                         tty_port_tty_set(&acm->port, NULL);
                         acm_tty_unregister(acm);
@@ -582,6 +583,7 @@ static void acm_tty_close(struct tty_struct *tty, struct file *filp)
         acm_port_down(acm);
         tty_port_close_end(&acm->port, tty);
         tty_port_tty_set(&acm->port, NULL);
+        mutex_unlock(&open_mutex);
 }
 
 static int acm_tty_write(struct tty_struct *tty,