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=-2.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, 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 6D592C11D05 for ; Thu, 20 Feb 2020 14:42:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3CA5A2068F for ; Thu, 20 Feb 2020 14:42:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="KdAg/woS" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728300AbgBTOm5 (ORCPT ); Thu, 20 Feb 2020 09:42:57 -0500 Received: from mail-pj1-f65.google.com ([209.85.216.65]:38169 "EHLO mail-pj1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728051AbgBTOm4 (ORCPT ); Thu, 20 Feb 2020 09:42:56 -0500 Received: by mail-pj1-f65.google.com with SMTP id j17so975728pjz.3 for ; Thu, 20 Feb 2020 06:42:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=RxnSL1NXcKi7I7bNcJCdW9on2O0BYdTsZJtPIT2pvYw=; b=KdAg/woSNMrUJKRcLFFlI+Q+hVITLMcpG7XScyuKG/rch8DT0ixv0D566k0F6Otle5 cwUJ9HRiFzGxwadC2OGhYKlbi8DY37VVlVByUznCM/ePQqloA5GZa8o7dH6LoSlCXELI xHiS0Znal9Y94kgjTYg3T4vhf7VfZdwXuuPNSPTmiXi4+qhzVsVlHLDZkmlgCghwM4Qa v/WrYtjYP4COBB8qs8urercROMOjnOGNsoVyT/j5NP0Fb21SDV41DG9fE+HNMOMetTAQ XgnS9s+qEWkZbksqv0i8KVXCGOJjkUmEpAupdro45WGRn4iCF6kChpGXyfcBCSocK02A s3bg== 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=RxnSL1NXcKi7I7bNcJCdW9on2O0BYdTsZJtPIT2pvYw=; b=HmNyh+r24fZ9RSh8WlBS40g+zFzZrQ2IUYJn+iJbq4RbLPchNGuf8kH1qBj0hpHxcg sJqOgrk1635PLppXaDsWYLI7pNPv+tnw+nBWaSTzwpsQI43Se3ggktQdxVNoUmQsCvug zPkiT0teiRoRVtVgDJaL+x+zQRt3FCHii+3TImZkww9BYryoNd529W8w/LtVNh9wTkiw 50K+MONTFqxt48EYvKSDma22TsCFUYcRz3Ahdsokrr7zwqqUTD8+OCrecjyEKUrss4B/ voDDd2EDGIbOrGuNL8GtGTAMnSzOIqBTMWOhLKlRtRSHtlHEnN3c9YSM9BabB6vVUXN2 g9EA== X-Gm-Message-State: APjAAAVSTf32Quh+NFLzHUPLnB0+1kaluaypx4EpQo7oHmSQwpUdvHP7 i3Onc+FpB03/Ph+bwfTnJlw= X-Google-Smtp-Source: APXvYqz3wBILWTKaw7OWLHGCjDgI2EKdZTlM2RKtM4tMDi6g9DoPS8Zonk8MclzuCyaioif8icLXpA== X-Received: by 2002:a17:90a:a385:: with SMTP id x5mr4099539pjp.102.1582209774753; Thu, 20 Feb 2020 06:42:54 -0800 (PST) Received: from localhost ([43.224.245.179]) by smtp.gmail.com with ESMTPSA id b5sm3770299pfb.179.2020.02.20.06.42.53 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Thu, 20 Feb 2020 06:42:54 -0800 (PST) Date: Thu, 20 Feb 2020 22:42:51 +0800 From: chenqiwu To: Vincent Guittot Cc: Ingo Molnar , Peter Zijlstra , Juri Lelli , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , linux-kernel , chenqiwu Subject: Re: [PATCH] sched/fair: add !se->on_rq check before dequeue entity Message-ID: <20200220144251.GA15604@cqw-OptiPlex-7050> References: <1582183784-13502-1-git-send-email-qiwuchen55@gmail.com> <20200220100915.GA14721@cqw-OptiPlex-7050> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > Hmm i have been too quick in my reply. I wanted to say: > AFAICT, there is no other way to dequeue a task from a cfs_rq for > which the group entity is not enqueued But we should notice the potential racy pathes called by deactivate_task(). For example: One path is dequeue a task from its cfs_rq called by schedule(): __schedule deactivate_task dequeue_task dequeue_task_fair Another path is trying to migrate the same task to a CPU on the preferred node: numa_migrate_preferred task_numa_migrate migrate_swap stop_two_cpus migrate_swap_stop __migrate_swap_task deactivate_task dequeue_task_fair There could be a racy if the task is dequeued form its cfs_rq in parallel.