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/synclinkmp.c b/drivers/char/synclinkmp.c
index ac447c7eb572..e56caf7d82aa 100644
--- a/drivers/char/synclinkmp.c
+++ b/drivers/char/synclinkmp.c
@@ -3365,7 +3365,9 @@ static int block_til_ready(struct tty_struct *tty, struct file *filp,
                         printk("%s(%d):%s block_til_ready() count=%d\n",
                                  __FILE__,__LINE__, tty->driver->name, port->count );
 
+                tty_unlock();
                 schedule();
+                tty_lock();
         }
 
         set_current_state(TASK_RUNNING);