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=-0.8 required=3.0 tests=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 D0354C433DF for ; Thu, 11 Jun 2020 01:32:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A5C21206A4 for ; Thu, 11 Jun 2020 01:32:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="rS9uqXeH" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726407AbgFKBc2 (ORCPT ); Wed, 10 Jun 2020 21:32:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53126 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726265AbgFKBc0 (ORCPT ); Wed, 10 Jun 2020 21:32:26 -0400 Received: from mail-qk1-x741.google.com (mail-qk1-x741.google.com [IPv6:2607:f8b0:4864:20::741]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B1107C08C5C1 for ; Wed, 10 Jun 2020 18:32:26 -0700 (PDT) Received: by mail-qk1-x741.google.com with SMTP id l17so4138565qki.9 for ; Wed, 10 Jun 2020 18:32:26 -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; bh=GeSX8BLi/S97GAEC8tAxV2cog3jQBy8w8/D9vd362qA=; b=rS9uqXeHK+Xy7MdjS3rdfJl0MwS489Fyt+KGbXqkfZ76nFlpp4WlT+0Q6Q97kN+utD NIpm0q2sOcAwnbUVv7kNi2jxljRQFqGythGpcKPox/HNRlSELB7wYnlsoWVxrrBx7Fxm 3Sl1pM2kSOIktiHNPpHNYjLtzyqg5xBEJY01I= 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; bh=GeSX8BLi/S97GAEC8tAxV2cog3jQBy8w8/D9vd362qA=; b=QoY2jyWu9Tt+IND2o+juVN4H+BVYH5ZcG8yAh1ofP0LHjmv0X56F0V5ztEqK9/ooY+ VYpbWTOso7wgeY7/MJ5paTSgDAHJfDwM6GfeAJbE0hiabUoB2d77h0UvBpeBIVjGrdbL n9dhviyh4SkgouL4Z5han/HJGiWuWZtKABPtvNts5CYYpbxz+t2hnzL0DSXrJ/6EnYG9 pQHLf7hGKiaiZOx8v5/3DcheJy/ztfkXZ4qE8VALhuGEc7zhJzl+KPd7i+bu0W2FB5Op 6P1hLbhxd3x9pSX/ng0896jtom0AoEge+gU6f9HZQQId+x2I07bOmyLK7Rvs3yabQu08 A6aA== X-Gm-Message-State: AOAM533FTKljA3G+/cL3mrz9E0DQl8NsH5ZILSc1Ht00g5umqnrBlrsW v475HZLZzGcN7fhgnl6h+loaJQ== X-Google-Smtp-Source: ABdhPJz6gg55lcd58w3pkrBwmi2gA9J36PIx1Nta5MymXsCxZ5SaU+egNwIauVSxFDB4LuccOVmNJA== X-Received: by 2002:a05:620a:52d:: with SMTP id h13mr5932452qkh.424.1591839145357; Wed, 10 Jun 2020 18:32:25 -0700 (PDT) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id 6sm1054724qkl.26.2020.06.10.18.32.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Jun 2020 18:32:24 -0700 (PDT) Date: Wed, 10 Jun 2020 21:32:24 -0400 From: Joel Fernandes To: "Paul E. McKenney" Cc: Frederic Weisbecker , LKML , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Josh Triplett Subject: Re: [PATCH 01/10] rcu: Directly lock rdp->nocb_lock on nocb code entrypoints Message-ID: <20200611013224.GA9005@google.com> References: <20200520122949.GB16672@google.com> <20200522175739.GM2869@paulmck-ThinkPad-P72> <20200604114121.GA26398@lenoir> <20200604163655.GC29598@paulmck-ThinkPad-P72> <20200608125715.GA30920@lenoir> <20200609180227.GR4455@paulmck-ThinkPad-P72> <20200610131238.GA26639@lenoir> <20200610140210.GT4455@paulmck-ThinkPad-P72> <20200610221245.GA3833@lenoir> <20200610232142.GA4455@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200610232142.GA4455@paulmck-ThinkPad-P72> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 10, 2020 at 04:21:42PM -0700, Paul E. McKenney wrote: [...] > > > 8. To softirq 3. Either GP or CB kthread for the transitioning > > > CPU advances to next. > > > At this point, the no-CBs setup is fully shut down. > > > 9. To softirq 4. Transitioning code advances to next, > > > which is the first, "In softirq". > > > (This one -might- be unnecessary, but...) > > > > > > All transitions are of course with the ->nocb_lock held. > > > > > > When there is only one CPU during early boot near rcu_init() time, > > > the transition from "In softirq" to "No-CB" can remain be instantaneous. > > > > > > This has the advantage of not slowing things down just because there > > > is an RCU callback flood in progress. It also uses an explicit > > > protocol that should (give or take bugs) maintain full safety both > > > in protection of ->cblist and in dealing with RCU callback floods. > > > > > > Thoughts? > > > > Agreed. And I really like that it details the whole process in a very > > explicit way. > > > > Thanks! > > Glad you like it! And of course please adjust it as needed, up to and > including doing something completely different that works better. ;-) Makes sense to me too, thanks! - Joel