From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1BC6EC433E0 for ; Tue, 21 Jul 2020 08:38:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E909F2080D for ; Tue, 21 Jul 2020 08:38:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="JG6kBeCP" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728475AbgGUIiD (ORCPT ); Tue, 21 Jul 2020 04:38:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56320 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726089AbgGUIiD (ORCPT ); Tue, 21 Jul 2020 04:38:03 -0400 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 128EAC061794 for ; Tue, 21 Jul 2020 01:38:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=YjXdkcialCHHTslIUxZppGWPfxGY86d3pVwVQzGRFxs=; b=JG6kBeCPB8nK5ZvMP2xPH0QUBF ciKSp4h49uh4d9269k51SaDz4dWqMPzjW3y4n/GutafvKzZdypnoZWiXyNsjxMn0pzguXzw6LMgDH edhIytrnsPRGNZeSHybFp8T+W5d8ZMhPkHaa0bh0G5dVhN6xY9tMUeuoc6wPVvBp0lbAu4DBWnvk3 HTnzJSHDeWE5/YNCgV6LLkd5seJKSXej7of2Gii1g/q6yIL2kWUwfmr+Au4iz2tx4IdYYpmQtSSna wI1tfyDT3btza9I5MI4FRpGIu/Ox9r9xQXiZYwZDwTvqIDosISEl1/FEInQix1qCOH5T/O6la92ye yhkV24OA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jxnmd-0007b5-6q; Tue, 21 Jul 2020 08:37:55 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 7AB04300446; Tue, 21 Jul 2020 10:37:53 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 66FCE23426BA1; Tue, 21 Jul 2020 10:37:53 +0200 (CEST) Date: Tue, 21 Jul 2020 10:37:53 +0200 From: peterz@infradead.org To: Paul Gortmaker Cc: Oleg Nesterov , Jiri Slaby , Christian Brauner , , "Eric W. Biederman" , Linux kernel mailing list , Mel Gorman , Dave Jones Subject: Re: 5.8-rc*: kernel BUG at kernel/signal.c:1917 Message-ID: <20200721083753.GH119549@hirez.programming.kicks-ass.net> References: <20200718171406.GB16791@redhat.com> <20200718174448.4btbjcvp6wbbdgts@wittgenstein> <20200720064326.GA6612@redhat.com> <20200720082657.GC6612@redhat.com> <20200720084106.GJ10769@hirez.programming.kicks-ass.net> <20200720105924.GE43129@hirez.programming.kicks-ass.net> <20200720140224.GD6612@redhat.com> <20200720142105.GR10769@hirez.programming.kicks-ass.net> <20200721045251.GA28481@windriver.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200721045251.GA28481@windriver.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 21, 2020 at 12:52:52AM -0400, Paul Gortmaker wrote: > [Re: 5.8-rc*: kernel BUG at kernel/signal.c:1917] On 20/07/2020 (Mon 16:21) Peter Zijlstra wrote: > > > On Mon, Jul 20, 2020 at 04:02:24PM +0200, Oleg Nesterov wrote: > > > I have to admit, I do not understand the usage of prev_state in schedule(), > > > it looks really, really subtle... > > > > Right, so commit dbfb089d360 solved a problem where schedule() re-read > > prev->state vs prev->on_rq = 0. That is, schedule()'s dequeue and > > ttwu()'s enqueue disagreed over sched_contributes_to_load. and as a > > result load-accounting went wobbly. > > > > Now, looking at that commit again, I might've solved the problem twice > > :-P > > [...] > > > That said, in a crossed email, I just proposed we could simplify all > > this like so.. but now I need to go ask people to re-validate that > > loadavg muck again :-/ > > After a two hour "quick" sanity test I then gave it a full 7h run (which > always seemed to break before dbfb089d360) and I didn't see any stuck > load average with master from today + this change. > > Paul. > > root@t5610:/home/paul/git/linux-head# > [1]+ Done nohup tools/testing/selftests/rcutorture/bin/kvm.sh --cpus 24 --duration 420 --configs TREE03 --trust-make > /tmp/kvm.sh.out 2>&1 > root@t5610:/home/paul/git/linux-head# cat /proc/version > Linux version 5.8.0-rc6-00001-g5714ee50bb43-dirty (paul@t5610) (gcc (Ubuntu 9.3.0-10ubuntu2) 9.3.0, GNU ld (GNU Binutils for Ubuntu) 2.34) #3 SMP Mon Jul 20 12:30:33 EDT 2020 > root@t5610:/home/paul/git/linux-head# uptime > 00:49:18 up 7:41, 2 users, load average: 0.01, 0.00, 0.63 > root@t5610:/home/paul/git/linux-head# > > -- Thanks a lot for re-testing that Paul, much appreciated! Let me go write a Changelog for this then...