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 0980CC433DF for ; Mon, 20 Jul 2020 06:56:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D5A6422CB2 for ; Mon, 20 Jul 2020 06:56:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="DL9mwDA7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726821AbgGTG4l (ORCPT ); Mon, 20 Jul 2020 02:56:41 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:26653 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725815AbgGTG4l (ORCPT ); Mon, 20 Jul 2020 02:56:41 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1595228199; 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=FGxfsH7JoYjo8uZ25QL7MHJ8zI5IrhXb8UDFK05X1AM=; b=DL9mwDA76NTgnEh89lqiAWYEp6CIqOUCokwKSwVYUszNaAg+scjhnHrtB0QdlAPkPDLLYn hnZTNy0rVBCTHvmkhdSG3gw6K2qVc5l9mpZRAs2wdOnL61zcCXsvUJHiWD6mxnqBg/Wu0k bX19ujrystojha/1AGyxbSeW6lysjag= 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-355-uz-DO6llPKelP1Kl2nFCvw-1; Mon, 20 Jul 2020 02:56:37 -0400 X-MC-Unique: uz-DO6llPKelP1Kl2nFCvw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 4D44D19057A8; Mon, 20 Jul 2020 06:56:36 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.40.192.147]) by smtp.corp.redhat.com (Postfix) with SMTP id 1007A1001B07; Mon, 20 Jul 2020 06:56:34 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 20 Jul 2020 08:56:35 +0200 (CEST) Date: Mon, 20 Jul 2020 08:56:33 +0200 From: Oleg Nesterov To: Jiri Slaby Cc: christian@brauner.io, "Eric W. Biederman" , Linux kernel mailing list Subject: Re: 5.8-rc*: kernel BUG at kernel/signal.c:1917 Message-ID: <20200720065633.GB6612@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> <0deb1081-299b-1475-f368-7ca65b535a9c@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0deb1081-299b-1475-f368-7ca65b535a9c@kernel.org> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 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: > > On 18. 07. 20, 19:14, Oleg Nesterov wrote: > > > > This is already wrong. But > > > > Where does this __might_sleep() come from ??? I ses no blocking calls > > in ptrace_stop(). Not to mention it is called with ->siglock held and > > right after this lock is dropped we take tasklist_lock. > > Decoded stacktrace: > > > ptrace_stop (include/linux/freezer.h:57 include/linux/freezer.h:67 include/linux/freezer.h:128 include/linux/freezer.h:173 kernel/signal.c:2217) > > ptrace_do_notify (kernel/signal.c:2272) > > ptrace_notify (arch/x86/include/asm/paravirt.h:656 arch/x86/include/asm/qspinlock.h:55 include/linux/spinlock.h:211 include/linux/spinlock_api_smp.h:167 include/linux/spinlock.h:403 kernel/signal.c:2282) > > syscall_trace_enter (include/linux/tracehook.h:73 include/linux/tracehook.h:104 arch/x86/entry/common.c:159) > > do_syscall_64 (arch/x86/entry/common.c:380) > > entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:124) > > It is try_to_freeze_unsafe in try_to_freeze in freezable_schedule in > ptrace_stop. Aha, thanks a lot! try_to_freeze_unsafe() is called after schedule() which must return with ->state = RUNNING, so this matches another WARN_ON(current->state) added by debugging patch after freezable_schedule(). Somehow I decided __might_sleep() was called before read_unlock/schedule. > > > > How this connects to the debugging patch I sent? Did you see this warning > > without that patch? > > I suppose this made it appear: > +CONFIG_PREEMPT_COUNT=y > -# CONFIG_DEBUG_ATOMIC_SLEEP is not set > +CONFIG_DEBUG_ATOMIC_SLEEP=y I see, > Please see my other e-mail, all this is with dbfb089d360b applied. Maybe > it makes more sense now? Yes. Thanks Jiri! Oleg.