From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751823Ab0KBKZ4 (ORCPT ); Tue, 2 Nov 2010 06:25:56 -0400 Received: from hera.kernel.org ([140.211.167.34]:40196 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751251Ab0KBKZu (ORCPT ); Tue, 2 Nov 2010 06:25:50 -0400 Message-ID: <4CCFE7C1.60909@kernel.org> Date: Tue, 02 Nov 2010 11:28:17 +0100 From: Tejun Heo User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); en-US; rv:1.9.2.12) Gecko/20101027 Lightning/1.0b2 Thunderbird/3.1.6 MIME-Version: 1.0 To: Arnd Bergmann CC: James Cloos , Eli Billauer , Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: open() on /dev/tty takes 30 seconds on 2.6.36 References: <4CCBCD8E.1020601@billauer.co.il> <201010310436.18613.arnd@arndb.de> <201010311236.38844.arnd@arndb.de> In-Reply-To: <201010311236.38844.arnd@arndb.de> X-Enigmail-Version: 1.1.1 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Tue, 02 Nov 2010 10:25:09 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On 10/31/2010 12:36 PM, Arnd Bergmann wrote: > On Sunday 31 October 2010, James Cloos wrote: >> WARNING: at kernel/workqueue.c:1180 worker_enter_idle+0xd6/0xe2() >> Hardware name: MS-7642 >> Modules linked in: tcp_diag inet_diag ipt_addrtype xt_dscp xt_string xt_owner xt_multiport xt_iprange xt_hashlimit xt_DSCP xt_NFQUEUE xt_mark xt_connmark tun snd_pcm_oss snd_mixer_oss snd_usb_audio snd_usbmidi_lib snd_rawmidi tpm_tis tpm ppdev parport_pc tpm_bios parport serio_raw edac_core k10temp pcspkr i2c_piix4 shpchp >> Pid: 8061, comm: kworker/0:1 Not tainted 2.6.36-carbon1 #18 >> Call Trace: >> [] warn_slowpath_common+0x85/0x9d >> [] warn_slowpath_null+0x1a/0x1c >> [] worker_enter_idle+0xd6/0xe2 >> [] worker_thread+0x182/0x19b >> [] ? worker_thread+0x0/0x19b >> [] kthread+0x82/0x8a >> [] kernel_thread_helper+0x4/0x10 >> [] ? kthread+0x0/0x8a >> [] ? kernel_thread_helper+0x0/0x10 >> ---[ end trace 756b0818a6415dca ]--- >> >> That was followed by a number of task blocked for more than 120 seconds >> messages, all due to waiting for pty input or output. An example trace: > > This is triggered by an internal check in the workqueue handling that > Tejun introduced. I guess it might be possible that this is triggered by > a worker thread being blocked on a mutex, but I don't understand > exactly what it is checking for. Hmmm... that's a condition which shouldn't happen regardless of being blocked on mutex or whatever. It means that internal book keeping used to manage concurrency went out of sync somehow. I've re-read the code managing nr_running but couldn't spot where the problem could be. Is there any way to reproduce the problem? Thanks. -- tejun