Messages in this thread | | | Subject | Re: [linux-next / tty] possible circular locking dependency detected | From | Vegard Nossum <> | Date | Sat, 3 Jun 2017 22:50:19 +0200 |
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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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