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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 67ED1C433EF for ; Tue, 19 Jun 2018 14:24:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2D74C204EC for ; Tue, 19 Jun 2018 14:24:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2D74C204EC Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757216AbeFSOYD (ORCPT ); Tue, 19 Jun 2018 10:24:03 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:51394 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757102AbeFSOYB (ORCPT ); Tue, 19 Jun 2018 10:24:01 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D75EA1596; Tue, 19 Jun 2018 07:24:00 -0700 (PDT) Received: from e108498-lin.cambridge.arm.com (e108498-lin.cambridge.arm.com [10.1.211.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E33803F557; Tue, 19 Jun 2018 07:23:56 -0700 (PDT) Date: Tue, 19 Jun 2018 15:23:51 +0100 From: Quentin Perret To: Peter Zijlstra Cc: rjw@rjwysocki.net, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, mingo@redhat.com, dietmar.eggemann@arm.com, morten.rasmussen@arm.com, chris.redpath@arm.com, patrick.bellasi@arm.com, valentin.schneider@arm.com, vincent.guittot@linaro.org, thara.gopinath@linaro.org, viresh.kumar@linaro.org, tkjos@google.com, joelaf@google.com, smuckle@google.com, adharmap@quicinc.com, skannan@quicinc.com, pkondeti@codeaurora.org, juri.lelli@redhat.com, edubezval@gmail.com, srinivas.pandruvada@linux.intel.com, currojerez@riseup.net, javi.merino@kernel.org Subject: Re: [RFC PATCH v3 03/10] PM: Introduce an Energy Model management framework Message-ID: <20180619142351.GA29374@e108498-lin.cambridge.arm.com> References: <20180521142505.6522-1-quentin.perret@arm.com> <20180521142505.6522-4-quentin.perret@arm.com> <20180619113408.GQ2458@hirez.programming.kicks-ass.net> <20180619125857.GY17720@e108498-lin.cambridge.arm.com> <20180619132338.GF2476@hirez.programming.kicks-ass.net> <20180619133844.GB17720@e108498-lin.cambridge.arm.com> <20180619141642.GE2494@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180619141642.GE2494@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.8.3 (2017-05-23) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday 19 Jun 2018 at 16:16:42 (+0200), Peter Zijlstra wrote: > On Tue, Jun 19, 2018 at 02:38:45PM +0100, Quentin Perret wrote: > > But maybe I could use something simpler than a lock in this case ? > > Would WRITE_ONCE/READ_ONCE be enough to ensure that atomicity for > > example ? > > Yes, since its a single pointer, smp_store_release() + READ_ONCE() > should be sufficient (these are the foundations of RCU). OK, good, I'll get rid of the spinlock in v4 (and read more about RCU foundations then :-)) Thanks, Quentin