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=-5.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 68035C433E4 for ; Mon, 20 Jul 2020 06:43:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4529722B4D for ; Mon, 20 Jul 2020 06:43:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="HDnSr4SF" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726884AbgGTGnh (ORCPT ); Mon, 20 Jul 2020 02:43:37 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:55294 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725805AbgGTGng (ORCPT ); Mon, 20 Jul 2020 02:43:36 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1595227415; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ciF2+1AsFOhctkHIotBDF5T5LP3R/nd9/VEpQ+S2kN4=; b=HDnSr4SFCsRhkfCxDVGLmCJ1hmQMaigcXsgLRvmD3q1/hWohdz0IlVhKBaOn13t6mRinSZ o2SSzG7kwUi/4YZ5tJ9WZl5x0/or+QYh0/swl8RFG2iag6ll+kfetW6LsVf/qqHXJsTW3m 6wR/GgWxmU6r51wzgDH7BSQGWj9i288= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-394-hXXR15E0ORa6kVV3b1X2jg-1; Mon, 20 Jul 2020 02:43:33 -0400 X-MC-Unique: hXXR15E0ORa6kVV3b1X2jg-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 02482106B245; Mon, 20 Jul 2020 06:43:31 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.40.192.147]) by smtp.corp.redhat.com (Postfix) with SMTP id 04F7478526; Mon, 20 Jul 2020 06:43:27 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 20 Jul 2020 08:43:30 +0200 (CEST) Date: Mon, 20 Jul 2020 08:43:26 +0200 From: Oleg Nesterov To: Jiri Slaby Cc: Christian Brauner , christian@brauner.io, "Eric W. Biederman" , Linux kernel mailing list , Peter Zijlstra , Mel Gorman , Dave Jones , Paul Gortmaker Subject: Re: 5.8-rc*: kernel BUG at kernel/signal.c:1917 Message-ID: <20200720064326.GA6612@redhat.com> References: <6b253b55-586d-0bc4-9f58-c45c631abc60@kernel.org> <5a8c4c38-7aeb-981a-8d3b-a7a5c8ca5564@kernel.org> <20200717122651.GA6067@redhat.com> <20200717124017.GB6067@redhat.com> <2c8ef23c-43b4-39d4-8e84-92769c948da9@kernel.org> <20200718171406.GB16791@redhat.com> <20200718174448.4btbjcvp6wbbdgts@wittgenstein> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/20, Jiri Slaby wrote: > > You tackled it, we cherry-picked dbfb089d360 to our kernels. Ccing more > people. Thanks... so with this patch __schedule() does prev_state = prev->state; ... if (!preempt && prev_state && prev_state == prev->state) { if (signal_pending_state(prev_state, prev)) { prev->state = TASK_RUNNING; } else { and ptrace_freeze_traced() can change ->state in between. This means that this task can return from __schedule() with ->state != RUNNING, this can explain BUG_ON(task_is_stopped_or_traced) in do_notify_parent() you reported. Oleg.