From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935289AbXGQPt6 (ORCPT ); Tue, 17 Jul 2007 11:49:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759244AbXGQPtu (ORCPT ); Tue, 17 Jul 2007 11:49:50 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:34369 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758372AbXGQPtt (ORCPT ); Tue, 17 Jul 2007 11:49:49 -0400 Date: Tue, 17 Jul 2007 17:49:34 +0200 From: Ingo Molnar To: Jeremy Fitzhardinge Cc: linux-kernel@vger.kernel.org, Andrew Morton , Linus Torvalds , stable@kernel.org, Greg KH , Chris Wright Subject: [patch] fix the softlockup watchdog to actually work Message-ID: <20070717154934.GA24231@elte.hu> References: <20070717114453.GA8212@elte.hu> <469CCF8F.4010107@goop.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <469CCF8F.4010107@goop.org> User-Agent: Mutt/1.5.14 (2007-02-12) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.0.3 -1.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Jeremy Fitzhardinge wrote: > Ingo Molnar wrote: > > Subject: softlockup: fix Xen bogosity > > From: Ingo Molnar > > > > this Xen related commit: > > > > Well, not just Xen. It relates to any virtual environment: kvm, > lguest, vmi, xen... (Not that they all implement a measure of > unstolen time.) > > How about a more descriptive patch title, along the lines of > "softlockup watchdog: fix rate limiting"? uhm, the problem was that it did not work _at all_, not something about 'rate limiting'. Yes, i got quite a bit grumpy when i found this, because you completely broke the softlockup watchdog via a pretty intrusive commit and you apparently didnt even do a minimal check whether its functionality was preserved! Updated patch for Andrew/Linus and for -stable attached. Ingo -----------------------------> Subject: fix the softlockup watchdog to actually work From: Ingo Molnar this Xen related commit: commit 966812dc98e6a7fcdf759cbfa0efab77500a8868 Author: Jeremy Fitzhardinge Date: Tue May 8 00:28:02 2007 -0700 Ignore stolen time in the softlockup watchdog broke the softlockup watchdog to never report any lockups. (!) print_timestamp defaults to 0, this makes the following condition always true: if (print_timestamp < (touch_timestamp + 1) || and we'll in essence never report soft lockups. apparently the functionality of the soft lockup watchdog was never actually tested with that patch applied ... [this is -stable material too.] Signed-off-by: Ingo Molnar --- kernel/softlockup.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) Index: linux/kernel/softlockup.c =================================================================== --- linux.orig/kernel/softlockup.c +++ linux/kernel/softlockup.c @@ -79,10 +79,11 @@ void softlockup_tick(void) print_timestamp = per_cpu(print_timestamp, this_cpu); /* report at most once a second */ - if (print_timestamp < (touch_timestamp + 1) || - did_panic || - !per_cpu(watchdog_task, this_cpu)) + if ((print_timestamp >= touch_timestamp && + print_timestamp < (touch_timestamp + 1)) || + did_panic || !per_cpu(watchdog_task, this_cpu)) { return; + } /* do not print during early bootup: */ if (unlikely(system_state != SYSTEM_RUNNING)) {