From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Hurley Subject: Re: [PATCH v4 00/32] ldisc patchset Date: Thu, 21 Feb 2013 08:38:30 -0500 Message-ID: <1361453910.10685.7.camel@thor.lan> References: <1360095638-6624-1-git-send-email-peter@hurleysoftware.com> <1361390599-15195-1-git-send-email-peter@hurleysoftware.com> <51261E30.9040907@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from mailout02.c08.mtsvc.net ([205.186.168.190]:59620 "EHLO mailout02.c08.mtsvc.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753719Ab3BUNiw (ORCPT ); Thu, 21 Feb 2013 08:38:52 -0500 In-Reply-To: <51261E30.9040907@gmail.com> Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: Sasha Levin Cc: Greg Kroah-Hartman , Jiri Slaby , Sebastian Andrzej Siewior , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, Ilya Zykov , Dave Jones , Michael Ellerman , Shawn Guo On Thu, 2013-02-21 at 08:16 -0500, Sasha Levin wrote: > On 02/20/2013 03:02 PM, Peter Hurley wrote: > > Sasha and Dave, my trinity testbeds die in other areas right now; > > I would really appreciate if you would please re-test this series. > > Hi Peter, > > I saw this twice in overnight fuzzing: > > [ 1473.912280] ================================= > [ 1473.913180] [ BUG: bad contention detected! ] > [ 1473.914071] 3.8.0-next-20130220-sasha-00038-g1ad55df-dirty #8 Tainted: G W > [ 1473.915684] --------------------------------- > [ 1473.916549] kworker/1:1/361 is trying to contend lock (&tty->ldisc_sem) at: > [ 1473.918031] [] tty_ldisc_ref+0x1f/0x60 > [ 1473.919060] but there are no locks held! Ahh, of course. That explains why the rwsem trylock doesn't track lock stats -- because by the time lock_contended() is called, up_write() could have just called lockdep_release(), so that it appears as if the lock has been released when in fact it has not but is about to. I'll just remove the lock contention test from the trylocks. Thanks, Peter > [ 1473.919813] > [ 1473.919813] other info that might help us debug this: > [ 1473.920044] 2 locks held by kworker/1:1/361: > [ 1473.920044] #0: (events){.+.+.+}, at: [] process_one_work+0x228/0x6a0 > [ 1473.920044] #1: ((&buf->work)){+.+...}, at: [] process_one_work+0x228/0x6a0 > [ 1473.920044] > [ 1473.920044] stack backtrace: > [ 1473.920044] Pid: 361, comm: kworker/1:1 Tainted: G W 3.8.0-next-20130220-sasha-00038-g1ad55df-dirty #8 > [ 1473.920044] Call Trace: > [ 1473.920044] [] ? tty_ldisc_ref+0x1f/0x60 > [ 1473.920044] [] print_lock_contention_bug+0xf6/0x110 > [ 1473.920044] [] lock_contended+0x213/0x4e0 > [ 1473.920044] [] ldsem_down_read_trylock+0xb1/0xc0 > [ 1473.920044] [] tty_ldisc_ref+0x1f/0x60 > [ 1473.920044] [] flush_to_ldisc+0x37/0x1a0 > [ 1473.920044] [] process_one_work+0x366/0x6a0 > [ 1473.920044] [] ? process_one_work+0x228/0x6a0 > [ 1473.920044] [] worker_thread+0x238/0x370 > [ 1473.920044] [] ? rescuer_thread+0x310/0x310 > [ 1473.920044] [] kthread+0xe3/0xf0 > [ 1473.920044] [] ? flush_kthread_work+0x1f0/0x1f0 > [ 1473.920044] [] ret_from_fork+0x7c/0xb0 > [ 1473.920044] [] ? flush_kthread_work+0x1f0/0x1f0 > > > Thanks, > Sasha