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=-5.8 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,URIBL_BLOCKED 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 2296EC4320A for ; Wed, 28 Jul 2021 18:40:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0204760184 for ; Wed, 28 Jul 2021 18:40:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230315AbhG1Skf (ORCPT ); Wed, 28 Jul 2021 14:40:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41338 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230233AbhG1Ske (ORCPT ); Wed, 28 Jul 2021 14:40:34 -0400 Received: from mail-ed1-x533.google.com (mail-ed1-x533.google.com [IPv6:2a00:1450:4864:20::533]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C454AC061757 for ; Wed, 28 Jul 2021 11:40:31 -0700 (PDT) Received: by mail-ed1-x533.google.com with SMTP id j2so4537520edp.11 for ; Wed, 28 Jul 2021 11:40:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=hMGQipmv4P+6hTmePxpJ22V8LdLQi3CACmtx2vw04NE=; b=I/BCzuCVYSBhj+aO3Q4aWDfu6lLss36Xk4btqlTUWsx3V8as8ycmR+abRAbzInVD8U GZDoL0hQAv0JekGQ4xpA79Nb5tqPYhOcZIv9ILu9WWKb+/T0f2DcATTLmdswj0vh5QcO Lfd7SkdRPLRnQBiwbNH1OwFXVCq2MJZiHhG4o= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=hMGQipmv4P+6hTmePxpJ22V8LdLQi3CACmtx2vw04NE=; b=qhbQKsCsIbubML6q+ksXpnVXb2uqZPHIafVB6ap8mSZnBZRUMfGswMaGhHxQz6LyMT mA0oKA9+9ppGVpEBNYGNyUWIOyRTnj8DrtelNq4v5Iy/Vlroo/+46ZNWOLI9+uOhHHSI nlrRsFM1+cpDu/E8tINMODjYdJQ4t98jDXZw388it9iq5nkLY7ZrfU4kHofr2mZYS5LH eBppTCJPev8T3OOWt+tx6bBp999dh4FLI6onieGENZY7yybAbPTGzgffeR+KeIj2EX60 K4GkWMVOs9+/lwNXIx+ZaV9yVJ+4pdgl//l5L2zDgM2pcRYTjnWkVbMoJ5pk32mmy3MP FUMg== X-Gm-Message-State: AOAM532xS5FixLJh6iaV+ukRRL6M3p0adTKq6f1ole51swaWnIP7v15E /JAdoPmGBANUaUUgDXUzkXX/kPlah5h4rNWSByY= X-Google-Smtp-Source: ABdhPJxVHfUyTM13m0F6ZEv9Aj940rJvBFmgk8USVAlI2K84r+GWTnW2+6h4yriU9AUwUZ6NLzPJjA== X-Received: by 2002:aa7:d296:: with SMTP id w22mr1475308edq.170.1627497630295; Wed, 28 Jul 2021 11:40:30 -0700 (PDT) Received: from mail-ed1-f52.google.com (mail-ed1-f52.google.com. [209.85.208.52]) by smtp.gmail.com with ESMTPSA id j24sm231216edp.44.2021.07.28.11.40.30 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 28 Jul 2021 11:40:30 -0700 (PDT) Received: by mail-ed1-f52.google.com with SMTP id da26so4607308edb.1 for ; Wed, 28 Jul 2021 11:40:30 -0700 (PDT) X-Received: by 2002:a2e:9241:: with SMTP id v1mr660028ljg.48.1627497136138; Wed, 28 Jul 2021 11:32:16 -0700 (PDT) MIME-Version: 1.0 References: <20210721202042.GA1472052@paulmck-ThinkPad-P17-Gen-1> <20210721202127.2129660-4-paulmck@kernel.org> <20210728173715.GA9416@paulmck-ThinkPad-P17-Gen-1> <1810346528.8990.1627495925037.JavaMail.zimbra@efficios.com> In-Reply-To: <1810346528.8990.1627495925037.JavaMail.zimbra@efficios.com> From: Linus Torvalds Date: Wed, 28 Jul 2021 11:32:00 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 rcu 04/18] rcu: Weaken ->dynticks accesses and updates To: Mathieu Desnoyers Cc: paulmck , rcu , linux-kernel , kernel-team , Ingo Molnar , Lai Jiangshan , Andrew Morton , Josh Triplett , Thomas Gleixner , Peter Zijlstra , rostedt , David Howells , Eric Dumazet , fweisbec , Oleg Nesterov , "Joel Fernandes, Google" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 28, 2021 at 11:12 AM Mathieu Desnoyers wrote: > > Are the percpu atomics you have in mind different from what is found in > Documentation/core-api/this_cpu_ops.rst ? > > Namely this_cpu_add_return(pcp, val) in this case. Nope. Those are only "CPU-atomic", ie atomic wrt interrupts etc. The RCU code wants SMP-atomic, and it's mainly that we *could* do the addressing more efficiently. Linus