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=-5.3 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,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 68A3EC43461 for ; Fri, 11 Sep 2020 11:36:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 044A9221E7 for ; Fri, 11 Sep 2020 11:36:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="k2uKWpn7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725803AbgIKLgJ (ORCPT ); Fri, 11 Sep 2020 07:36:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54238 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725834AbgIKLf5 (ORCPT ); Fri, 11 Sep 2020 07:35:57 -0400 Received: from mail-pg1-x544.google.com (mail-pg1-x544.google.com [IPv6:2607:f8b0:4864:20::544]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 79BDCC061796 for ; Fri, 11 Sep 2020 04:35:37 -0700 (PDT) Received: by mail-pg1-x544.google.com with SMTP id 7so6438116pgm.11 for ; Fri, 11 Sep 2020 04:35:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=KycsOi7S4N/nBLooPbnXXSV4SR9wjUe6iCxexLVUCD0=; b=k2uKWpn7H//jNXvjMwXc7Bg+qjc/gvdqG5U6MePPIbX38khfArh8ol3jLT/BX51pKG 1v3YBzNb6OY1HA4cCTarS0p2U+55oNdx8wHzNQNTdywjvXUqeX/T4Qq+Oo0nJdqLEXXv NLFLJmbh7joqZC21BYFlrWwOj8MNI6mtyde2GPs21/0qXrWNq4j5+y0EZV30oAhGjQR8 HWyipnRynroPOf5h4JwI4Z1gvd3kOMjgdK7af+zgdR2RTV0cgrTXPRuV3X6PgZDGhgKX qqw3ySvUcUtBVOcxCTYsHvaNH0OODb0Y491W60rm+Pt+6mqkz64QwIHWHFJPou1RbwiX jULw== 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=KycsOi7S4N/nBLooPbnXXSV4SR9wjUe6iCxexLVUCD0=; b=YDiC57fnJcNCTfMbOmFzya+XtyKqhEBbodRC2kDDG6ylBKtaMLir78og8LzHX/lGik qgvfC4iHe5ytT3QZaFRG7ErsqOy5fZRhgnDKdcLsZhL0oiXZs0eCs8EWQ9h4fio8tZf2 48LgdvSCVBNnDwSyOm7K7K70+WLtUIy4JlRUGg40ii30PAEpql1mevYhNdJfNjahAeSO 1xfTpU3djYmuI0/LTYeiaoRZE+7P+sKb694b7CMCXrZxkZuil0FNYrKuQgCsMgjhu1vI pHdgPrYI45nfKHfuaC7KmrfBx+Kw/efZkxLHrGILfRmDZ2B9OHyF4cGtIJ/sUXNay0zf fkzA== X-Gm-Message-State: AOAM5326Ne73NHWiKs86jiiEUB9cU8w243HToN17Kp/Itg6CM0t7TRoO m3O7lEGQonu9dd461b+vO7cW2w== X-Google-Smtp-Source: ABdhPJyyXvGwFaQdsNQbM6++Ut33lLn/dd07b1UkP/3vxznU7kfEoDReiBe9Y7J9oQkDfJu82o1sSw== X-Received: by 2002:a17:902:c151:: with SMTP id 17mr1638319plj.49.1599824136816; Fri, 11 Sep 2020 04:35:36 -0700 (PDT) Received: from localhost ([122.181.54.133]) by smtp.gmail.com with ESMTPSA id z4sm2109200pfr.197.2020.09.11.04.35.35 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 11 Sep 2020 04:35:35 -0700 (PDT) Date: Fri, 11 Sep 2020 17:05:32 +0530 From: Viresh Kumar To: peterz@infradead.org Cc: Rafael Wysocki , linux-pm@vger.kernel.org, Vincent Guittot , Lukasz Luba , cristian.marussi@arm.com, sudeep.holla@arm.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/4] cpufreq: stats: Defer stats update to cpufreq_stats_record_transition() Message-ID: <20200911113532.zq2bou4swixb2ymk@vireshk-i7> References: <973bd0536c4957d03f36447398498cfacb2393d9.1599031227.git.viresh.kumar@linaro.org> <20200911101132.GC165568@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200911101132.GC165568@hirez.programming.kicks-ass.net> User-Agent: NeoMutt/20180716-391-311a52 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On 11-09-20, 12:11, peterz@infradead.org wrote: > On Wed, Sep 02, 2020 at 12:54:41PM +0530, Viresh Kumar wrote: > > + atomic_t reset_pending; > > > + atomic_set(&stats->reset_pending, 0); > > + if (atomic_read(&stats->reset_pending)) > > + bool pending = atomic_read(&stats->reset_pending); > > + atomic_set(&stats->reset_pending, 1); > > + bool pending = atomic_read(&stats->reset_pending); > > + if (atomic_read(&stats->reset_pending)) > > What do you think atomic_t is doing for you? I was trying to avoid races while two writes are going in parallel, but obviously as this isn't a RMW operation, it won't result in anything for me. Maybe what I should be doing is just READ_ONCE()/WRITE_ONCE()? So the other side doesn't see any intermediate value that was never meant to be set/read ? -- viresh