From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757399Ab3A2PeD (ORCPT ); Tue, 29 Jan 2013 10:34:03 -0500 Received: from mx1.redhat.com ([209.132.183.28]:17945 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757305Ab3A2Pd7 (ORCPT ); Tue, 29 Jan 2013 10:33:59 -0500 Date: Tue, 29 Jan 2013 10:33:48 -0500 From: Don Zickus To: Mike Lykov Cc: Andrew Morton , Ingo Molnar , Thomas Gleixner , linux-kernel@vger.kernel.org, linux-watchdog@vger.kernel.org, kirill@shutemov.name Subject: Re: [BUG?] false positive in soft lockup detector while unlzma initramfs on slow cpu Message-ID: <20130129153348.GR98867@redhat.com> References: <5107D1D3.6040105@yandex.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5107D1D3.6040105@yandex.ru> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Mike, On Tue, Jan 29, 2013 at 05:42:43PM +0400, Mike Lykov wrote: > > So my questions: > > 1. Are there a BUG in soft lockup detection mechanizm? Changing > watchdog_thresh to 30 have a side effect in production - D-state > userspace processes will be detected slowly. Are there a need to > detecting soft lockups at boot time? Maybe it need after initramfs > boot only when userspace processes begin to work? The softlockup mechanism works scheduling a high priority task that kicks the softlockups. If the unzip thread is taking too long, it could accidentally trip the detection. Seeing that you are running on a 600 MHz machine, it could be possible. Though I am not entirely sure how the scheduling works for decompressing the initramfs. I wouldn't think it is that high of a priority. > > 2. How to change watchdog_thresh parameter at boot without patching > sources? If it necessary (with it side effects) maybe implement it > as commandline parameter or config compile time parameter? I attached a patch below that allows you to set it a boot time. Let me know if this works for you, then I can clean it up and post it properly. Cheers, Don diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 75a2ab3..e448d63 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -79,6 +79,14 @@ static int __init softlockup_panic_setup(char *str) } __setup("softlockup_panic=", softlockup_panic_setup); +static int __init watchdog_thresh_setup(char *str) +{ + watchdog_thresh = simple_strtoul(str, NULL, 0); + + return 1; +} +__setup("watchdog_thresh=", watchdog_thresh_setup); + static int __init nowatchdog_setup(char *str) { watchdog_enabled = 0;