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 0E758C4338F for ; Wed, 28 Jul 2021 18:32:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E49206103A for ; Wed, 28 Jul 2021 18:32:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229581AbhG1ScW (ORCPT ); Wed, 28 Jul 2021 14:32:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39462 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229556AbhG1ScW (ORCPT ); Wed, 28 Jul 2021 14:32:22 -0400 Received: from mail-lf1-x129.google.com (mail-lf1-x129.google.com [IPv6:2a00:1450:4864:20::129]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 424E9C061757 for ; Wed, 28 Jul 2021 11:32:20 -0700 (PDT) Received: by mail-lf1-x129.google.com with SMTP id a26so5683130lfr.11 for ; Wed, 28 Jul 2021 11:32:20 -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=nejppcR1M04wie7U0NYbEYkhsRFs4WfpN1UJK4OeXNXUAxPTxQdiOUpT8xuwOoC7U/ BfTMFoftN7iOo3t4k1GUgyWoLtSXseJT6b9C18fGCU7m6lmYCEqKFV+PeuDPM25LQyvN 5HMe/a20UKFqRtfiiVDVsHLNKRFYfO3CxexwTFjc2qdIILH2s6zi7iGcn4o3mq21SuaV xgRC/f5UVWffjLYL6uL+yC9vW22MJiqCRObG3ZgpwVnG9NtlF5K4Ff7CcYSF23RdVw3W adLad5F5cefs8owGdM83sNjphhgtq0z0avcWfXRD6oPAunCG2oDgiGS4craQA+SLHBmK KziA== X-Gm-Message-State: AOAM533oNvHeE+vG9NqudXlr3l+hL88BADK2ZrJXkVRo031vwu7WJj3d flb+zt/K/CqBRzKM6iLJHNimGpqx0TuTt1XYw3A= X-Google-Smtp-Source: ABdhPJxZHb3dFz06FyrwThvhkj+WIxS50Q0LhOQxJ/K9Pd3Tc3f636IWy9IIWiZtq2sDX2r1elsxyQ== X-Received: by 2002:a05:6512:3b89:: with SMTP id g9mr683124lfv.96.1627497138530; Wed, 28 Jul 2021 11:32:18 -0700 (PDT) Received: from mail-lj1-f177.google.com (mail-lj1-f177.google.com. [209.85.208.177]) by smtp.gmail.com with ESMTPSA id r4sm67287lfm.214.2021.07.28.11.32.16 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 28 Jul 2021 11:32:16 -0700 (PDT) Received: by mail-lj1-f177.google.com with SMTP id a7so4182831ljq.11 for ; Wed, 28 Jul 2021 11:32:16 -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: rcu@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