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=-3.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 3E368C43387 for ; Fri, 28 Dec 2018 01:54:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 098BD21479 for ; Fri, 28 Dec 2018 01:54:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1545962041; bh=qYH5nXiB7VtYJwX11IKtH8YK3mdVnesyo48B11TqTgU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=IKlgFDP4zWkxddXHc/DGyONbGcVIfcFbnlWDOa+y3TQLpoGo83C78tBfDgVAPL69k b+vegjnQF6+y0zMs8pXB+SO+XDmD99XLA/fgSp5KmkcVwHMA9T1Roqifx260nL35wu dh9Ss44b2pyHvy7gB7eK64uLYsR+oRUt1Jxb6WtA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726665AbeL1Bx5 (ORCPT ); Thu, 27 Dec 2018 20:53:57 -0500 Received: from mail-yb1-f196.google.com ([209.85.219.196]:42671 "EHLO mail-yb1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725910AbeL1Bx5 (ORCPT ); Thu, 27 Dec 2018 20:53:57 -0500 Received: by mail-yb1-f196.google.com with SMTP id q145so6397565ybq.9 for ; Thu, 27 Dec 2018 17:53:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=OH9MX3Sq0jk+b04xP5ckr2KqMpSRmTXQoGrW5fnfpcM=; b=nY8arMf0frjH/2g3XxKgiNF5g5BR7q095UWNgVVQvmAhXxgU47D5I95/Q9GE00yPtG B5Em7CwDVE3F0Zqybg2gQcEoUCSWpgFJMx1XbZx3GIYijZYbs8R4F5/ickH0RGpgdJRD 32e9UG+Ke1j73hwq7WzbyIH1Gj86cj7xVkVU+eh9DcQI21ZFj/2I3Iuj+zfpJyJ7CB1j kzcEEFeUUKeJgdqkjaEvuDZQXgHt53qkPo0j1G8X785QWQ2pC3tprfQe6y60kd5ohWP9 GjJd2RnssopurKA+P9jrGpzVvEkONYpSMSPOOB29f6le0veyQ/rrsG4+qZ60X+Q0GCMB T1Kg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=OH9MX3Sq0jk+b04xP5ckr2KqMpSRmTXQoGrW5fnfpcM=; b=txqZScloyZ98IisYOnqw6kaDlppVzXUGH47pyAkgkkmT4RVHOz1/wDtYmvjNbdSbVS CcRLfMV4Hv5ZMHI+WxH4tYsyrt1SkVmvJhQDRGAEZ5vAA7irrK6+/b8kPIArWewIOD6b 2DlyUeMq0CzOSXdNJp+dSmmzwsD2bQInm+9cSb9/v3sT08H64C3Ho364K0e8siJZCDo3 zcc0oQ450z3WVY1xwmx18Yq59945VPw6t4xRJXEEf65BRgMgW7MIVdooHprw8UNrS5wQ LLmmSyWDBzAPhCCqan7f8PFUB/q53BfYhNyuU+oH42w7xgznDvImGjxg+TqJwDQDX1hU Vghw== X-Gm-Message-State: AA+aEWZisfTQKLjDLri4gsDTtd1XKngF+8gBh2VPEBJLRxntVbje+qmw clWpR0VcsvRMZ8vhF4a8b+o= X-Google-Smtp-Source: AFSGD/XSHSiKusivYrLZNCd357i9zlM2CCIM1EvJUFXgPrBxPey6U2aTwZ0lyzYUsaL2pJBEunpv2w== X-Received: by 2002:a25:4f89:: with SMTP id d131mr26272650ybb.218.1545962035919; Thu, 27 Dec 2018 17:53:55 -0800 (PST) Received: from localhost ([2620:10d:c091:180::1:7729]) by smtp.gmail.com with ESMTPSA id c127sm16236550ywb.67.2018.12.27.17.53.54 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 27 Dec 2018 17:53:54 -0800 (PST) Date: Thu, 27 Dec 2018 17:53:52 -0800 From: Tejun Heo To: Linus Torvalds Cc: Vincent Guittot , Sargun Dhillon , Xie XiuQi , Ingo Molnar , Peter Zijlstra , xiezhipeng1@huawei.com, huawei.libin@huawei.com, linux-kernel , Dmitry Adamushko , Rik van Riel Subject: Re: [PATCH] sched: fix infinity loop in update_blocked_averages Message-ID: <20181228015352.GG2509588@devbig004.ftw2.facebook.com> References: <1545879866-27809-1-git-send-email-xiexiuqi@huawei.com> <20181227102107.GA21156@linaro.org> <20181228011524.GF2509588@devbig004.ftw2.facebook.com> 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 Hello, On Thu, Dec 27, 2018 at 05:36:47PM -0800, Linus Torvalds wrote: > > Unless I'm totally confused, which is definitely possible, I don't > > think there's a race condition and the only bug is the > > tmp_alone_branch pointer getting dangled, which maybe doesn't happen > > all that much? > > Ahh. That would explain the list corruption. The next > list_add_leaf_cfs_rq() could try to add to a removed entry. > > How would you reset it? Do something like > > rq->tmp_alone_branch = &rq->leaf_cfs_rq_list; > > for every removal, or make it conditional on it matching the removed entry? Vincent knows that part way better than me but I think the safest way would be doing the optimization removal iff tmp_alone_branch is already pointing to leaf_cfs_rq_list. IIUC, it's pointing to something else only while a branch is being built and deferring optimization removal by an avg update cycle isn't gonna make any difference anyway. Thanks. -- tejun