Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 027CAC38142 for ; Tue, 31 Jan 2023 19:58:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231569AbjAaT6Q (ORCPT ); Tue, 31 Jan 2023 14:58:16 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57876 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229468AbjAaT6P (ORCPT ); Tue, 31 Jan 2023 14:58:15 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 325BB10ABD for ; Tue, 31 Jan 2023 11:58:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=0Boqe77xXw/WW6/Jx9IzSgzEvG7AsRtZEZ4We5AQ2oY=; b=gI25N3EUJYmiNAQBK3q8AnSBDE 7L4MN1uk34doF7bYxOUAQ2SE0jH3ShvXili1sCp+XAi6jaAdi4XMKAI8zhHXGDXR7XM5fYB+coGn3 8kOOfcw+BLqZR/y7Hb/fcV6sA1R1krlWimbsw2RBkI5E63mQm1n8v3TmK6OqYnzoYCrkl7D7NcnVW v0zKa+gzmq/wgTspAbsKVd1DsWzhulvgqVluwo/RmM7g6lLFfrEG0uPQo8LBPpOIQh8Rfi4mYlhZ/ 5Wv9oKXuqXAs6ULw4qPQXzZ9r8EKMeEJhjsha1wI5i+F5r6Kj2JvIt9n0NRGysJI9F1NGt4JX1snz oQg82jeA==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1pMwlU-00BcdF-S0; Tue, 31 Jan 2023 19:58:01 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 6C175300577; Tue, 31 Jan 2023 20:57:59 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 370BD20D6DE1C; Tue, 31 Jan 2023 20:57:59 +0100 (CET) Date: Tue, 31 Jan 2023 20:57:59 +0100 From: Peter Zijlstra To: Thomas Gleixner Cc: Yu Liao , fweisbec@gmail.com, mingo@kernel.org, liwei391@huawei.com, adobriyan@gmail.com, mirsad.todorovac@alu.unizg.hr, linux-kernel@vger.kernel.org Subject: Re: [PATCH RFC] tick/nohz: fix data races in get_cpu_idle_time_us() Message-ID: References: <20230128020051.2328465-1-liaoyu15@huawei.com> <87357q228f.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87357q228f.ffs@tglx> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 31, 2023 at 03:44:00PM +0100, Thomas Gleixner wrote: > P.S.: I hate the spinlock in the idle code path, but I don't have a > better idea. seqcount? It would avoid the obvious interleave and put most of the onus on the reader (which never happens anyway).