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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 22ECFC35DEE for ; Tue, 25 Feb 2020 02:12:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E210521927 for ; Tue, 25 Feb 2020 02:12:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="Jk1CqHzQ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728757AbgBYCMW (ORCPT ); Mon, 24 Feb 2020 21:12:22 -0500 Received: from mail-qk1-f193.google.com ([209.85.222.193]:33362 "EHLO mail-qk1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726962AbgBYCMW (ORCPT ); Mon, 24 Feb 2020 21:12:22 -0500 Received: by mail-qk1-f193.google.com with SMTP id h4so10663599qkm.0 for ; Mon, 24 Feb 2020 18:12:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=aV1wtzsixyxbIlgwZVMjWFxlrGFi0X1sLLQ6AvkFw1M=; b=Jk1CqHzQBnOMrF2X0s+N5OdS4ebnoq+q2+n71ELYrkrblxYD9qjWtUaZmVOHPduZuI 1L5Va9/zeze48RCRMN+cfSWsT025ckOaGJcLgdDarI76+j27MlzRzUgRajMIR4ctLzy+ QqWW4Tq+WqrKM0qSiXYwvYW+auRw5ETve76eU= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=aV1wtzsixyxbIlgwZVMjWFxlrGFi0X1sLLQ6AvkFw1M=; b=CAXObHEhaZ+SgwxRJrCk4jno3+n9a//MXGRcuy8be1ZzW3QGDfIgWhfVFrzshLKwIZ f8EnBjgLuf0gxSOQD26T7STukBxBaDCMI3c//n3KPcu8UuJ6ewJxYLPtPF1X6FoeHLEt 10m24ruzDY2PVCyGQhXXYUMGYqHKWSFbnrz/op62jM9QeHcaKmTrOidB8/1RHq57onDP fpTsGQTsOCYqcMk1IzSe4+BJHNWIIHCZdgSzoDav4xs0EHpY20O3cTUny8pSEfVtDK/M HgNVH0ejNIcyPJ9hQ1YTTBQqL021lgvGMHMKqbG7NF+v04cVchRuSIxGXsGQvv6GSmBR sFRw== X-Gm-Message-State: APjAAAWOHfvi3KXRpoBS3LJK7s4IdVt/geH+2I7jueMutMON+TjHGI88 Fb8gM4zmTkGJE7OcFpEZdO9Fvznmti4= X-Google-Smtp-Source: APXvYqxAJO1y+PRZqaNlPLjpP+h9ynxxQ1fDyUoGCsEl+wBDpiS2urRyLKsL3UMT7hyRdnrkk9GNJw== X-Received: by 2002:a37:c07:: with SMTP id 7mr53621921qkm.414.1582596741329; Mon, 24 Feb 2020 18:12:21 -0800 (PST) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id v7sm6856624qkg.103.2020.02.24.18.12.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Feb 2020 18:12:20 -0800 (PST) Date: Mon, 24 Feb 2020 21:12:20 -0500 From: Joel Fernandes To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, rostedt@goodmis.org, mingo@kernel.org, gregkh@linuxfoundation.org, gustavo@embeddedor.com, tglx@linutronix.de, paulmck@kernel.org, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, luto@kernel.org, tony.luck@intel.com, frederic@kernel.org, dan.carpenter@oracle.com, mhiramat@kernel.org Subject: Re: [PATCH v4 01/27] lockdep: Teach lockdep about "USED" <- "IN-NMI" inversions Message-ID: <20200225021220.GD253171@google.com> References: <20200221133416.777099322@infradead.org> <20200221134215.090538203@infradead.org> <20200222030843.GA191380@google.com> <20200224101050.GE14897@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200224101050.GE14897@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 24, 2020 at 11:10:50AM +0100, Peter Zijlstra wrote: > On Fri, Feb 21, 2020 at 10:08:43PM -0500, Joel Fernandes wrote: > > On Fri, Feb 21, 2020 at 02:34:17PM +0100, Peter Zijlstra wrote: > > > nmi_enter() does lockdep_off() and hence lockdep ignores everything. > > > > > > And NMI context makes it impossible to do full IN-NMI tracking like we > > > do IN-HARDIRQ, that could result in graph_lock recursion. > > > > The patch makes sense to me. > > > > Reviewed-by: Joel Fernandes (Google) > > > > NOTE: > > Also, I was wondering if we can detect the graph_lock recursion case and > > avoid doing anything bad, that way we enable more of the lockdep > > functionality for NMI where possible. Not sure if the suggestion makes sense > > though! > > Yeah, I considered playing trylock games, but figured I shouldn't make > it more complicated that it needs to be. Yes, I agree with you. Thanks. - Joel