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_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 A6ED3C43387 for ; Wed, 16 Jan 2019 17:32:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 79FB920675 for ; Wed, 16 Jan 2019 17:32:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727388AbfAPRce (ORCPT ); Wed, 16 Jan 2019 12:32:34 -0500 Received: from mx1.redhat.com ([209.132.183.28]:57752 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727122AbfAPRcd (ORCPT ); Wed, 16 Jan 2019 12:32:33 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 90DE7285BB; Wed, 16 Jan 2019 17:32:33 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.162]) by smtp.corp.redhat.com (Postfix) with SMTP id 3505D5D967; Wed, 16 Jan 2019 17:32:31 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Wed, 16 Jan 2019 18:32:33 +0100 (CET) Date: Wed, 16 Jan 2019 18:32:30 +0100 From: Oleg Nesterov To: "Kohli, Gaurav" Cc: Qian Cai , Peter Zijlstra , Ingo Molnar , linux kernel Subject: Re: kernel BUG at kernel/sched/core.c:3490! Message-ID: <20190116173229.GA20060@redhat.com> References: <20190107135215.GG14122@hirez.programming.kicks-ass.net> <46089f1c-ad72-c96c-2f35-c2f60e726462@lca.pw> <20190107175644.GB7636@redhat.com> <3a6d8f4c-d7ed-e888-601b-a379efec306a@codeaurora.org> <1547223444.6911.19.camel@lca.pw> <5a65a014-9013-cfbd-48a9-67199d33e719@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5a65a014-9013-cfbd-48a9-67199d33e719@codeaurora.org> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Wed, 16 Jan 2019 17:32:33 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/12, Kohli, Gaurav wrote: > > HI Peter, Oleg, > > as per flag and state this seems to be possible only from below code: Not sure I understand you, > XXX: 0 1 0x40844c > PF_NOFREEZE > PF_RANDOMIZE > PF_SIGNALED > PF_FORKNOEXEC > PF_EXITING > PF_EXITPIDONE > > above state shows do_exit runs properely and if somehow after parked stated > , TASK_WAKEKILL got set and signal_pending_state returns 1 in below case: > > switch_count = &prev->nivcsw; > if (!preempt && prev->state) { > if (unlikely(signal_pending_state(prev->state, prev))) { > prev->state = TASK_RUNNING; > } else { > deactivate_task(rq, prev, DEQUEUE_SLEEP | > DEQUEUE_NOCLOCK); or task->state was TASK_RUNNING when __schedule() was called, or the deactivated dead task was woken up later... The only problem is that every case looks "obviously impossible" ;) I have no idea whats going on, I can only suggest more stupid debugging patches which might narrow the problem. Oleg.