From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.8 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 510497D90D for ; Thu, 29 Aug 2019 13:59:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727454AbfH2N7N (ORCPT ); Thu, 29 Aug 2019 09:59:13 -0400 Received: from mail-pl1-f193.google.com ([209.85.214.193]:44428 "EHLO mail-pl1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727626AbfH2N7K (ORCPT ); Thu, 29 Aug 2019 09:59:10 -0400 Received: by mail-pl1-f193.google.com with SMTP id t14so1605477plr.11 for ; Thu, 29 Aug 2019 06:59:09 -0700 (PDT) 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=40EqMQd0G4SVbrZfGPeA5SE4upLhPO04pKe2ongbivs=; b=B7vedP+381Vda1eCJ1DpCKGye34MvOP4SaLRfcWFXrezjckDaL2DCJkysvbc5x6x9K 5ZHaAq8dolDDtXD5Emsjg2p4yLOStQjh6ER9RX2SxOPJPrpxQ9KcL7NtxmBaNUHUfkqr 9SWPCrsL1tOOGwTXDBiFQSW/yOhdLnH2Y9d3g= 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=40EqMQd0G4SVbrZfGPeA5SE4upLhPO04pKe2ongbivs=; b=rm+dI48Z1FuPsJDKdjzYphKlb88Ujg3BbZ4ha49y7V1rsg8jZwHUqGoEZyQ8/yBAz7 pxh5TG9IjcF6DNzWp2gQCdBCXM4OsoK9I53e9+v+WzE50DYL4jmAXGOgz0YQA+ReUtdK SXO71dOTm1NsJ1ZzxVenXDBeB0dSgjPNKjxYb1gTsudhioTAQmpIzskZzWb3XLbEodOj auaB/qREQ/cQ2QpeRFUp+7yxo5KnjwbYOxKHs9feHTzUnEPfTcU5NkqzYVyoZzCkaLtm 8UVv7rIQ+hFNYJV1S877Um02+gXhUVuBpiH0aaFNKP7HYdJBm6oOt+ETKQzZl+8HCPlr Wf+Q== X-Gm-Message-State: APjAAAWLagis9jg26PYfBrNagZp3zE3YcDy3rO6rGMRXbXqtRTjzOJRG YRfdY6oVecITbmZ8vJQ4mdTtDg== X-Google-Smtp-Source: APXvYqyN3H4PkVt4D8iZLYVpLv8rCMjL0d2y1VW3RXuJ+ApI39d4sYSpewllOECHNz60vokFKp1bBQ== X-Received: by 2002:a17:902:223:: with SMTP id 32mr10245894plc.220.1567087149497; Thu, 29 Aug 2019 06:59:09 -0700 (PDT) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id dw7sm2200431pjb.21.2019.08.29.06.59.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Aug 2019 06:59:08 -0700 (PDT) Date: Thu, 29 Aug 2019 09:59:07 -0400 From: Joel Fernandes To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, Frederic Weisbecker , Jonathan Corbet , Josh Triplett , kernel-team@android.com, Lai Jiangshan , linux-doc@vger.kernel.org, Mathieu Desnoyers , Mauro Carvalho Chehab , rcu@vger.kernel.org, Steven Rostedt Subject: Re: [RFC v1 2/2] rcu/tree: Remove dynticks_nmi_nesting counter Message-ID: <20190829135907.GC63638@google.com> References: <5d648897.1c69fb81.5e60a.fc70@mx.google.com> <20190828202330.GS26530@linux.ibm.com> <20190828210525.GB75931@google.com> <20190828211904.GX26530@linux.ibm.com> <20190828214241.GD75931@google.com> <20190828220108.GC26530@linux.ibm.com> <20190828221444.GA100789@google.com> <20190828231247.GE26530@linux.ibm.com> <20190829015155.GB100789@google.com> <20190829034336.GD4125@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190829034336.GD4125@linux.ibm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Wed, Aug 28, 2019 at 08:43:36PM -0700, Paul E. McKenney wrote: [snip] > On the tracing patch... That patch might be a good idea regardless, > but I bet that the reason that you felt the sudden need for it was due > to the loss of information in your eventual ->dynticks_nesting field. > After all, the value 0x1 might be an interrupt from idle, or it might > just as easily be a task running in the kernel at process level. True, however what really triggered me to do it was the existing code which does not distinguish between entry/exit from USER and IDLE. > The reason the patch might nevertheless be a good idea is that redundant > information can be helpful when debugging. Especially when debugging > new architecture-specific code, which is when RCU's dyntick-idle warnings > tend to find bugs. Sure, and also that it is more readable to ordinary human beings than "++=" and "--=" :-D. thanks, - Joel