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/serial/68360serial.c b/drivers/serial/68360serial.c
index edcf1cc089d..0dff3bbddc8 100644
--- a/drivers/serial/68360serial.c
+++ b/drivers/serial/68360serial.c
@@ -1860,7 +1860,9 @@ 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();
         }
         current->state = TASK_RUNNING;
         remove_wait_queue(&info->open_wait, &wait);