tty: release BTM while sleeping in block_til_ready

Most tty drivers may block while opening a device.
Since this possibly depends on another thread
closing it first and both threads may need the BTM,
we need to release it here.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/char/amiserial.c b/drivers/char/amiserial.c
index 8228e61bb54d..a11c8c9ca3d4 100644
--- a/drivers/char/amiserial.c
+++ b/drivers/char/amiserial.c
@@ -1710,7 +1710,9 @@ static int block_til_ready(struct tty_struct *tty, struct file * filp,
                 printk("block_til_ready blocking: ttys%d, count = %d\n",
                        info->line, state->count);
 #endif
+                tty_unlock();
                 schedule();
+                tty_lock();
         }
         __set_current_state(TASK_RUNNING);
         remove_wait_queue(&info->open_wait, &wait);