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=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 2C5DEC433E0 for ; Fri, 3 Jul 2020 11:36:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0860E20772 for ; Fri, 3 Jul 2020 11:36:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="TnJbmMtl" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726281AbgGCLgP (ORCPT ); Fri, 3 Jul 2020 07:36:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44734 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726022AbgGCLgP (ORCPT ); Fri, 3 Jul 2020 07:36:15 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C6EBDC08C5C1 for ; Fri, 3 Jul 2020 04:36:14 -0700 (PDT) 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=BRmHDFS/bl7K2f11+G87TQqmBoQlHFzbNhHFpvrEgZE=; b=TnJbmMtlYIRn5TgsQ6FuWoTaOx aaOLzsXKlb5lXbmd5aaVvLelDE2t/OYdSMqK+QsEpVNowiwAZBa7Req9LrSYABCP6cfYkMBcWzpjg OfynZIv63p4j6ZdJCquqHVBi8Dqlg/5U+SUmu6A/oOHlaASRX1yOXkAe4F50ueu0vR8YTCcH2YoPp GqUooo0/bcxlBNY1/ES2yURT/TaYCFBlkKG4/ZLPyVGnqpxnXsB6T5zPmzNQYKej92GqSqOohEFFW YOT7zBLWrwv4/ofBlr/Mr9burN3+VpcKckgjfwaBJgwTWNpQvRYsPpX2T/BX0g8b0RXWRAndzb+7L s62TEPiw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jrJzA-0008Vx-79; Fri, 03 Jul 2020 11:36:04 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 74C6B301124; Fri, 3 Jul 2020 13:36:03 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 40AFA21476E77; Fri, 3 Jul 2020 13:36:03 +0200 (CEST) Date: Fri, 3 Jul 2020 13:36:03 +0200 From: Peter Zijlstra To: Valentin Schneider Cc: Ingo Molnar , linux-kernel@vger.kernel.org, vincent.guittot@linaro.org, mgorman@suse.de, Oleg Nesterov , david@fromorbit.com Subject: Re: [RFC][PATCH] sched: Better document ttwu() Message-ID: <20200703113603.GL117543@hirez.programming.kicks-ass.net> References: <20200702125211.GQ4800@hirez.programming.kicks-ass.net> <20200703083012.GU4800@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200703083012.GU4800@hirez.programming.kicks-ass.net> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 03, 2020 at 10:30:12AM +0200, Peter Zijlstra wrote: > On Thu, Jul 02, 2020 at 07:39:16PM +0100, Valentin Schneider wrote: > > > @@ -3134,8 +3274,12 @@ static inline void prepare_task(struct task_struct *next) > > > /* > > > * Claim the task as running, we do this before switching to it > > > * such that any running task will have this set. > > > + * > > > + * __schedule()'s rq->lock and smp_mb__after_spin_lock() orders this > > > + * store against prior state change of @next, also see > > > + * try_to_wake_up(), specifically smp_load_acquire(&p->on_cpu). > > > > smp_*cond*_load_acquire(&p->on_cpu, ) > > Both, but yeah.. arguably the cond one is the more important one. Ah no, this one really want to match the WF_ON_CPU case. I'll clarify non-the-less.