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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 3D730C55179 for ; Wed, 28 Oct 2020 21:44:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D4D30246CD for ; Wed, 28 Oct 2020 21:44:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="DCpptmVv" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727144AbgJ1VoY (ORCPT ); Wed, 28 Oct 2020 17:44:24 -0400 Received: from merlin.infradead.org ([205.233.59.134]:60078 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726920AbgJ1VoU (ORCPT ); Wed, 28 Oct 2020 17:44:20 -0400 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=RcoHc6ioxIJHRLjyoIAWbgcMWvY3wzGmR282L3Znkso=; b=DCpptmVv4mZATOp9w7gcazeapY d+U5ktRYCztpocpf/4LDVXTMeM7/7NzPH7i+LDPLZBLRDMJAP0wWyfr6ula8PZEnQsNzD7t6g/MOb DcfXxUPD+sVNkf8VpE0EJDWif5ejxViCBraLN4XvLUmKUuSS23ZCXc4S5VFPXiGqoVlbaD1/gzoSM w7DvDeQVVLM/sFvtbAKs2Qfa5DnUs34MnvyeFqH8bI2Zv4v1jKCthfSRMlars4sxtZoPNToXmKU3G H5kP9688TYmUmR+msBoc9DOl3vc8iJ2eXKojKbECifY92ewQQrarqd7NBuAiPiFiSE3/kPWk+wrht 8tZ0xAQQ==; 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 1kXrKl-0002ac-T5; Wed, 28 Oct 2020 19:42:12 +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 49FA530018A; Wed, 28 Oct 2020 20:42:09 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 0604F2C114CE2; Wed, 28 Oct 2020 20:42:09 +0100 (CET) Date: Wed, 28 Oct 2020 20:42:08 +0100 From: Peter Zijlstra To: Chris Wilson Cc: linux-kernel@vger.kernel.org, linux-tip-commits@vger.kernel.org, tip-bot2 for Peter Zijlstra , Qian Cai , x86 , Boqun Feng Subject: Re: [tip: locking/core] lockdep: Fix usage_traceoverflow Message-ID: <20201028194208.GF2628@hirez.programming.kicks-ass.net> References: <20200930094937.GE2651@hirez.programming.kicks-ass.net> <160208761332.7002.17400661713288945222.tip-bot2@tip-bot2> <160379817513.29534.880306651053124370@build.alporthouse.com> <20201027115955.GA2611@hirez.programming.kicks-ass.net> <20201027123056.GE2651@hirez.programming.kicks-ass.net> <160380535006.10461.1259632375207276085@build.alporthouse.com> <20201027154533.GB2611@hirez.programming.kicks-ass.net> <160381649396.10461.15013696719989662769@build.alporthouse.com> <160390684819.31966.12048967113267928793@build.alporthouse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <160390684819.31966.12048967113267928793@build.alporthouse.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 28, 2020 at 05:40:48PM +0000, Chris Wilson wrote: > Quoting Chris Wilson (2020-10-27 16:34:53) > > Quoting Peter Zijlstra (2020-10-27 15:45:33) > > > On Tue, Oct 27, 2020 at 01:29:10PM +0000, Chris Wilson wrote: > > > > > > > <4> [304.908891] hm#2, depth: 6 [6], 3425cfea6ff31f7f != 547d92e9ec2ab9af > > > > <4> [304.908897] WARNING: CPU: 0 PID: 5658 at kernel/locking/lockdep.c:3679 check_chain_key+0x1a4/0x1f0 > > > > > > Urgh, I don't think I've _ever_ seen that warning trigger. > > > > > > The comments that go with it suggest memory corruption is the most > > > likely trigger of it. Is it easy to trigger? > > > > For the automated CI, yes, the few machines that run that particular HW > > test seem to hit it regularly. I have not yet reproduced it for myself. > > I thought it looked like something kasan would provide some insight for > > and we should get a kasan run through CI over the w/e. I suspect we've > > feed in some garbage and called it a lock. > > I tracked it down to a second invocation of lock_acquire_shared_recursive() > intermingled with some other regular mutexes (in this case ww_mutex). > > We hit this path in validate_chain(): > /* > * Mark recursive read, as we jump over it when > * building dependencies (just like we jump over > * trylock entries): > */ > if (ret == 2) > hlock->read = 2; > > and that is modifying hlock_id() and so the chain-key, after it has > already been computed. Ooh, interesting.. I'll have to go look at this in the morning, brain is fried already. Thanks for digging into it.