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=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 49CB5C0650E for ; Thu, 4 Jul 2019 08:00:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 298DC218AD for ; Thu, 4 Jul 2019 08:00:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726605AbfGDIAg convert rfc822-to-8bit (ORCPT ); Thu, 4 Jul 2019 04:00:36 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:58179 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725920AbfGDIAg (ORCPT ); Thu, 4 Jul 2019 04:00:36 -0400 Received: from bigeasy by Galois.linutronix.de with local (Exim 4.80) (envelope-from ) id 1hiwfS-0005fA-BH; Thu, 04 Jul 2019 10:00:34 +0200 Date: Thu, 4 Jul 2019 10:00:34 +0200 From: Sebastian Andrzej Siewior To: "xiaoqiang.zhao" Cc: linux-rt-users@vger.kernel.org Subject: Re: schdule bug in 4.4.38-rt49 Message-ID: <20190704080034.i6lztjc4ocykrwpy@linutronix.de> References: <55c68f08-4160-4bee-fdc5-9fc1ea86cf57@gmail.com> <20190703114256.3b52kbrududxq7vz@linutronix.de> <987eec05-14d0-29a5-723c-7bfbc0a5465b@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8BIT In-Reply-To: <987eec05-14d0-29a5-723c-7bfbc0a5465b@gmail.com> User-Agent: NeoMutt/20180716 Sender: linux-rt-users-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org On 2019-07-04 13:50:08 [+0800], xiaoqiang.zhao wrote: > > > > 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()', that is correct. I was saying that the preempt count was > 0 before wake_up() was invoked. > 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 ? correct. Sebastian