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=-2.5 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 E9795C5B57D for ; Fri, 5 Jul 2019 06:32:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B94B1218BA for ; Fri, 5 Jul 2019 06:32:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="uzMlcXpT" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727390AbfGEGcE (ORCPT ); Fri, 5 Jul 2019 02:32:04 -0400 Received: from mail-pf1-f196.google.com ([209.85.210.196]:46524 "EHLO mail-pf1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727291AbfGEGcE (ORCPT ); Fri, 5 Jul 2019 02:32:04 -0400 Received: by mail-pf1-f196.google.com with SMTP id 81so3842900pfy.13 for ; Thu, 04 Jul 2019 23:32:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:from:to:cc:references:message-id:date:user-agent :mime-version:in-reply-to:content-transfer-encoding:content-language; bh=ywnp2US7ZPK9SBTyG9Rjd35iFP/cy1G7vdtZ2d4neHM=; b=uzMlcXpTxxVoMl5JG8zZ2PkGzDeCJsJ+eWpOMw9T22TNZyXayL0jLynyJNYv8bgSH6 SsNqWiJykKnkkYkLQLASSwsfVSfAdkKhGRuwvPyKcXSeSYD/cMS85u3uWFeef5R5/RGn yFpmp7h5hIr/PJ7e2yG3HyigyqtsPkQFB6fT44TzvfOAjv8vwrvHfHAISYcS9X+Hs+tq G3F4dLBHm79YKTm6drlAxyG1mM1G23QCkhwWWH+pXKZ/MBnCG5uUvfEybtiFWcpNjnDA h8GDbjx0qijilF5jNaVgOGJB0eMqznFOqw9y5ibygDY4yE0iXkUMPdfvXZDfblBSeXJ3 wP3w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:from:to:cc:references:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=ywnp2US7ZPK9SBTyG9Rjd35iFP/cy1G7vdtZ2d4neHM=; b=sb3o8o8rfLrFtccc8MmprlqA/7o9GQG1bGIAYfm26yFe0ElxenVTx58tY0HTW51HAj vbneqtTnPd2O2ILCj2Mev8cej0SUMTfUKrSjk6jNHrtXPWcMfw/3U1Ur/SQ2udR95I7w JUFYoa5/Cfsnz7IvNST9TcAvU3Cs34dpagdbo80awEhGFMepdldmI+o1CjrTroaWmic2 d0i8Bpyl1BZjo6TQgS1na1nfWNZ+0nF3hYBIJbAQFaranwBxyBhuwJv3hDB4jY6fiFai HyDl1ktOF2MnGHWf213/o+D4K56K2DtlxNMtKDo8tqQstA197Y/yByLYPMdo6OXVgEIJ F42g== X-Gm-Message-State: APjAAAWG1+rgWrGuIDtfMWZPtCwyVISlybJly9VdRUZoityysKfOfSk3 nT6OnQVUbt05BR8uEnUx7lTMUXs86sc= X-Google-Smtp-Source: APXvYqyixsw/SGuVFPPorDKeXuA1K5AvsFWBJ3E/MSDoucrJNfLfTmqYBzKpZrAC35sMS26pNO3/EQ== X-Received: by 2002:a17:90a:32c7:: with SMTP id l65mr2891036pjb.1.1562308323307; Thu, 04 Jul 2019 23:32:03 -0700 (PDT) Received: from [10.11.32.138] ([43.230.89.66]) by smtp.gmail.com with ESMTPSA id o14sm20839489pfh.153.2019.07.04.23.32.01 (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Thu, 04 Jul 2019 23:32:02 -0700 (PDT) Subject: Re: schdule bug in 4.4.38-rt49 From: "xiaoqiang.zhao" To: Sebastian Andrzej Siewior Cc: linux-rt-users@vger.kernel.org References: <55c68f08-4160-4bee-fdc5-9fc1ea86cf57@gmail.com> <20190703114256.3b52kbrududxq7vz@linutronix.de> <987eec05-14d0-29a5-723c-7bfbc0a5465b@gmail.com> <3d020904-95c2-9cb1-1560-c1a2c931ba83@gmail.com> Message-ID: Date: Fri, 5 Jul 2019 14:31:59 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <3d020904-95c2-9cb1-1560-c1a2c931ba83@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-rt-users-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org 在 2019/7/4 下午6:17, xiaoqiang.zhao 写道: > Resend as plain-text to linux-rt-users list. > > 在 2019/7/4 下午1:50, xiaoqiang.zhao 写道: > > 在 2019/7/3 下午7:42, Sebastian Andrzej Siewior 写道: >> On 2019-06-26 15:35:04 [+0800], xiaoqiang.zhao wrote: >>> Hi, guys: >> Hi, >> > Thanks for your reply ;-) > >>> 2) -> __schedule_bug ( leads to kernel pagefault exception, OOPS!!) >>> >>> Before schedule, we have call preempt_disable twice, this will >>> definitely >>> bump preempt_count to 2 and >> >> something probably disabled preemption before that > > I feel this is not make sense.  In my opinion, the preempt_count must > be zero before we call 'schedule()', > > otherwise, in_atomic_preempt_off will return true and trigger the > __schedule_bug. If we have already > > disable_preempt, we may in atomic context and we should not call > schedule, right ? > >>> in_atomic_preempt_off will fail. >>> >>> I did not figure out:   WHY we call schedule inside >>> rt_spin_lock_slowlock >>> and under what condition this call is correct ? >> if the lock is acquired you schedule out and wait und it is available >> again. > got this. > > >> Finally, this issue is resolved by revert commit 80127a39681bd68c959f0953f84a830cbd7c3b1c .  This commit introduce a "preempt_disable()" call in "percpu_up_read" function and  can NOT coexist with 4.4.38-rt49 preempt-rt patch set Hope this information may be useful to someone who encounter the same problem ;-) Thanks Sebastian !