TITLE: possible deadlock in tty_buffer_flush
TYPE: LOCKDEP
CORRUPTED: Y

[ 1722.511384] ======================================================
[ 1722.511384] WARNING: possible circular locking dependency detected
[ 1722.511384] 4.12.0-rc2-next-20170529+ #1 Not tainted
[ 1722.511384] ------------------------------------------------------
[ 1722.511384] kworker/u4:2/58 is trying to acquire lock:
[ 1722.511384]  (&buf->lock){+.+...}, at: [<ffffffffa41b4e5b>] tty_buffer_flush+0xbb/0x3a0 drivers/tty/tty_buffer.c:221
[ 1722.511384] 
[ 1722.511384] but task is already holding lock:
[ 1722.511384]  (&o_tty->termios_rwsem/1){++++..}, at: [<ffffffffa41a5601>] isig+0xa1/0x4d0 drivers/tty/n_tty.c:1100
[ 1722.511384] 
[ 1722.511384] which lock already depends on the new lock.
