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| Started by | Vegard Nossum <vegard.nossum@oracle.com> |
|---|---|
| First post | 2017-05-29 12:50 +0200 |
| Last post | 2017-06-03 23:00 +0200 |
| Articles | 3 — 2 participants |
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Re: [linux-next / tty] possible circular locking dependency detected Vegard Nossum <vegard.nossum@oracle.com> - 2017-05-29 12:50 +0200
Re: [linux-next / tty] possible circular locking dependency detected Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-03 16:20 +0200
Re: [linux-next / tty] possible circular locking dependency detected Vegard Nossum <vegard.nossum@oracle.com> - 2017-06-03 23:00 +0200
| From | Vegard Nossum <vegard.nossum@oracle.com> |
|---|---|
| Date | 2017-05-29 12:50 +0200 |
| Subject | Re: [linux-next / tty] possible circular locking dependency detected |
| Message-ID | <tMqpk-72M-9@gated-at.bofh.it> |
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
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| From | Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
|---|---|
| Date | 2017-06-03 16:20 +0200 |
| Message-ID | <tOi4i-850-31@gated-at.bofh.it> |
| In reply to | #1652407 |
On Mon, May 29, 2017 at 12:43:39PM +0200, Vegard Nossum wrote:
> 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.
Any ideas? Or should I just revert the original patch?
thanks,
greg k-h
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| From | Vegard Nossum <vegard.nossum@oracle.com> |
|---|---|
| Date | 2017-06-03 23:00 +0200 |
| Message-ID | <tOojp-3mt-37@gated-at.bofh.it> |
| In reply to | #1656833 |
On 06/03/17 11:34, Greg Kroah-Hartman wrote:
> On Mon, May 29, 2017 at 12:43:39PM +0200, Vegard Nossum wrote:
>> 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.
>
> Any ideas? Or should I just revert the original patch?
I think we must revert it for now, as I can easily reproduce not just
the lockdep warning but actual hangs. It seems I missed some code paths
when I worked the original patch.
I'm working on a fix.
Vegard
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