From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755447AbZHUMaM (ORCPT ); Fri, 21 Aug 2009 08:30:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755059AbZHUMaL (ORCPT ); Fri, 21 Aug 2009 08:30:11 -0400 Received: from mail.windriver.com ([147.11.1.11]:48710 "EHLO mail.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754864AbZHUMaK (ORCPT ); Fri, 21 Aug 2009 08:30:10 -0400 Subject: Re: [PATCH] softlockup: fix problem with long kernel pauses from kgdb From: DDD To: Jason Wessel , Ingo Molnar Cc: Thomas Gleixner , Peter Zijlstra , lkml In-Reply-To: <20090804145909.GO7746@elte.hu> References: <4A6E0825.3020604@windriver.com> <1248725893.6987.2055.camel@twins> <4A6F139C.6070806@windriver.com> <20090804141623.GD7746@elte.hu> <4A784B78.2020801@windriver.com> <20090804145909.GO7746@elte.hu> Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Fri, 21 Aug 2009 20:42:21 +0800 Message-Id: <1250858541.24178.15.camel@dengdd-desktop> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 X-OriginalArrivalTime: 21 Aug 2009 12:29:45.0886 (UTC) FILETIME=[112AB3E0:01CA225B] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jason & Ingo, If we apply Peter's patch which was send out just a moment ago, I believe this issue will gone. :-) Thanks, Dongdong [PATCH -rt] timer: delay waking softirqs from the jiffy tick ... ... Signed-off-by: Peter Zijlstra --- kernel/timer.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/kernel/timer.c b/kernel/timer.c index 8137cce..96ac1b4 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -1221,10 +1221,10 @@ void update_process_times(int user_tick) /* Note: this timer irq context must be accounted for as well. */ account_process_tick(p, user_tick); + scheduler_tick(); run_local_timers(); if (rcu_pending(cpu)) rcu_check_callbacks(cpu, user_tick); - scheduler_tick(); run_posix_cpu_timers(p); } On Tue, 2009-08-04 at 16:59 +0200, Ingo Molnar wrote: > * Jason Wessel wrote: > > > Ingo Molnar wrote: > > > * Jason Wessel wrote: > > > > > >> ----- > > >> From: Jason Wessel > > >> Subject: [PATCH] softlockup: add sched_clock_tick() to avoid kernel warning on kgdb resume > > >> > > >> When CONFIG_HAVE_UNSTABLE_SCHED_CLOCK is set sched_clock() gets the > > >> time from hardware, such as from TSC. In this configuration kgdb will > > >> report a softlock warning messages on resuming or detaching from a > > >> debug session. > > >> > > > > > > Hm, this looks quite ugly. Peter, Thomas, can you think of a > > > cleaner solution? > > > > > > > Below was a more specific test case I received from Dongdong Deng > > which did not require kgdb. The test case is not something to > > merge, it is just a simple module to build to demonstrate the > > problem outside of kgdb. > > > > The patch I submitted might have been on the "ugly" side, but > > there was not an obvious way to solve the problem without making > > changes in kernel/sched*. I opted for something that was entirely > > self contained to the softlockup code. > > it's not really the fault of your patch really - all these > integrations along dynticks, scheduler time and softlockup feel a > bit awkward. Wondering whether there's some nicer way. > > Ingo