Re: [linux-next / tty] possible circular locking dependency detected

[Vegard Nossum]

On 05/22/17 12:27, Vegard Nossum wrote:
> On 05/22/17 12:24, Greg Kroah-Hartman wrote:
> > On Mon, May 22, 2017 at 04:39:43PM +0900, Sergey Senozhatsky wrote:
> > > Hello,
> > >
> > > [ 1274.378287] ======================================================
> > > [ 1274.378289] WARNING: possible circular locking dependency detected
> > > [ 1274.378290] 4.12.0-rc1-next-20170522-dbg-00007-gc09b2ab28b74-dirty 
> > > #1317 Not tainted
> > > [ 1274.378291] ------------------------------------------------------
> > > [ 1274.378293] kworker/u8:5/111 is trying to acquire lock:
> > > [ 1274.378294]  (&buf->lock){+.+...}, at: [<ffffffff812f2831>] 
> > > tty_buffer_flush+0x34/0x88
> > > [ 1274.378300]
> > >                 but task is already holding lock:
> > > [ 1274.378301]  (&o_tty->termios_rwsem/1){++++..}, at: 
> > > [<ffffffff812ee5c7>] isig+0x47/0xd2
> > > [ 1274.378307]
> > >                 which lock already depends on the new lock.
>
> > Any hint as to what you were doing when this happened?
> >
> > Does this also show up in 4.11?
>
> It's my patch "tty: fix port buffer locking" :-/
>
> At a glance, looks related to pty taking the lock on the other side in a
> different order. I'll have a closer look.

I can reproduce the lockdep report locally on v4.12-rc3. Looking at it now.


Vegard