1 files changed, 11 insertions, 14 deletions

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index dd8ae0cad1d5..c9a9ddd1d0bc 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -2122,6 +2122,17 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
         if (c < 0)
                 return c;
 
+        /*
+         *      Internal serialization of reads.
+         */
+        if (file->f_flags & O_NONBLOCK) {
+                if (!mutex_trylock(&ldata->atomic_read_lock))
+                        return -EAGAIN;
+        } else {
+                if (mutex_lock_interruptible(&ldata->atomic_read_lock))
+                        return -ERESTARTSYS;
+        }
+
         down_read(&tty->termios_rwsem);
 
         minimum = time = 0;
@@ -2141,20 +2152,6 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
                 }
         }
 
-        /*
-         *      Internal serialization of reads.
-         */
-        if (file->f_flags & O_NONBLOCK) {
-                if (!mutex_trylock(&ldata->atomic_read_lock)) {
-                        up_read(&tty->termios_rwsem);
-                        return -EAGAIN;
-                }
-        } else {
-                if (mutex_lock_interruptible(&ldata->atomic_read_lock)) {
-                        up_read(&tty->termios_rwsem);
-                        return -ERESTARTSYS;
-                }
-        }
         packet = tty->packet;
 
         add_wait_queue(&tty->read_wait, &wait);