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=-8.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 EC239C433E2 for ; Mon, 14 Sep 2020 22:04:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9FCED206F4 for ; Mon, 14 Sep 2020 22:04:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="F/dxBB+K" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726031AbgINWEW (ORCPT ); Mon, 14 Sep 2020 18:04:22 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:23794 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725994AbgINWEV (ORCPT ); Mon, 14 Sep 2020 18:04:21 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1600121059; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=2GhyD/cWEPiSDHqjdfHCn89vNoA2JN0oKHsy5Yj9ms0=; b=F/dxBB+K7aeYBwqz6DPdmq9LHHrFgbUwk5UAgMNVGmWPzz2Btf3QVNtX37QpfU5EqR+NcQ PZy2askIjbpwKQbz/FcvBdbI3JIoaCrUiqdhhfqOUMzlqL9T8RlTsAf4IsOtHgtD19uCpy jKiFmsrMrLV9w8rdVaeE8a9+q7eKe3w= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-596-Wvj6_w4WMWSq3SET62MF1Q-1; Mon, 14 Sep 2020 18:04:15 -0400 X-MC-Unique: Wvj6_w4WMWSq3SET62MF1Q-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 302661005E67; Mon, 14 Sep 2020 22:04:13 +0000 (UTC) Received: from ovpn-113-249.rdu2.redhat.com (ovpn-113-249.rdu2.redhat.com [10.10.113.249]) by smtp.corp.redhat.com (Postfix) with ESMTP id C46117BE76; Mon, 14 Sep 2020 22:04:08 +0000 (UTC) Message-ID: <269479609d444b2caebdc4d5d156bd5438a1899e.camel@redhat.com> Subject: Re: [RFC v7 12/19] lockdep: Add recursive read locks into dependency graph From: Qian Cai To: Boqun Feng , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org Cc: Peter Zijlstra , Ingo Molnar , Will Deacon , Jonathan Corbet , Waiman Long , Stephen Rothwell , linux-next@vger.kernel.org Date: Mon, 14 Sep 2020 18:04:08 -0400 In-Reply-To: <9b9780715a62d22a5229e9baae7e66a7f19d83eb.camel@redhat.com> References: <20200807074238.1632519-1-boqun.feng@gmail.com> <20200807074238.1632519-13-boqun.feng@gmail.com> <9b9780715a62d22a5229e9baae7e66a7f19d83eb.camel@redhat.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2020-09-14 at 14:16 -0400, Qian Cai wrote: > On Fri, 2020-08-07 at 15:42 +0800, Boqun Feng wrote: > > Since we have all the fundamental to handle recursive read locks, we now > > add them into the dependency graph. > > > > Signed-off-by: Boqun Feng > > Reverting this patch and its dependency: > > [14/19] lockdep: Take read/write status in consideration when generate > chainkey > > fixed a splat below. IOW, this patch introduced this new splat which looks Sorry, it turned out my previous reproducer was not so reliable, but now I found a new reliable reproducer that could trigger this on both x86 and powerpc every time which so far points out the culprit being the patchset: "[PATCH v1 0/5] seqlock: Introduce PREEMPT_RT support" [1]. It also matched exactly the exact timing (today) between the issue showed up and the patchset was merged into linux-next. I'll do a bit more confirmation and report it there. [1] https://lore.kernel.org/lkml/20200828010710.5407-1-a.darwish@linutronix.de/