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=-7.5 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 6E578C433E6 for ; Thu, 18 Mar 2021 18:06:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 297EC64F1D for ; Thu, 18 Mar 2021 18:06:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232445AbhCRSFb (ORCPT ); Thu, 18 Mar 2021 14:05:31 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:49482 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230164AbhCRSFE (ORCPT ); Thu, 18 Mar 2021 14:05:04 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1616090703; 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=WftQMrFPNAP4YAr6T6xNf+HYZqIB+G4C+TYDinLLNQA=; b=BM1KbF+EDz32kcFWmApUrXpYKNVRCuPB22sUqn5yzuaL+pSL3w3WQhPOwYgxdUQMoTdlIr /BubPA4Or4haI2FyQWNsCmH7f2P5IrPG8pJnBsROzaAWxAIRP72m1KNYyXvtGGNOqW1sAb 7rs9RZfPBDs18PxQh94l426xsR9nOQw= 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-367-bVL03gc7N26YbIhQwHfKxg-1; Thu, 18 Mar 2021 14:04:59 -0400 X-MC-Unique: bVL03gc7N26YbIhQwHfKxg-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8B67581A281; Thu, 18 Mar 2021 18:04:54 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.40.195.212]) by smtp.corp.redhat.com (Postfix) with SMTP id 473B460CDF; Thu, 18 Mar 2021 18:04:52 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 18 Mar 2021 19:04:54 +0100 (CET) Date: Thu, 18 Mar 2021 19:04:51 +0100 From: Oleg Nesterov To: qianli zhao Cc: christian@brauner.io, axboe@kernel.dk, "Eric W. Biederman" , Thomas Gleixner , Peter Collingbourne , linux-kernel@vger.kernel.org, Qianli Zhao Subject: Re: [PATCH V3] exit: trigger panic when global init has exited Message-ID: <20210318180450.GA9977@redhat.com> References: <1615985460-112867-1-git-send-email-zhaoqianligood@gmail.com> <20210317143805.GA5610@redhat.com> 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 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/18, qianli zhao wrote: > > Hi,Oleg > > Thank you for your reply. > > >> When init sub-threads running on different CPUs exit at the same time, > >> zap_pid_ns_processe()->BUG() may be happened. > > > and why do you think your patch can't prevent this? > > > Sorry, I must have missed something. But it seems to me that you are trying > > to fix the wrong problem. Yes, zap_pid_ns_processes() must not be called in > > the root namespace, and this has nothing to do with CONFIG_PID_NS. > > Yes, i try to fix this exception by test SIGNAL_GROUP_EXIT and call > panic before setting PF_EXITING to prevent zap_pid_ns_processes() > being called when init do_exit(). Ah, I didn't notice your patch does atomic_dec_and_test(signal->live) before exit_signals() which sets PF_EXITING. Thanks for correcting me. So yes, I was wrong, your patch can prevent this. Although I'd like to recheck if every do-something-if-group-dead action is correct in the case we have a non-PF_EXITING thread... But then I don't understand the SIGNAL_GROUP_EXIT check added by your patch. Do we really need it if we want to avoid zap_pid_ns_processes() when the global init exits? > In addition, the patch also protects the init process state to > successfully get usable init coredump. Could you spell please? Does this connect to SIGNAL_GROUP_EXIT check? Do you mean that you want to panic earlier, before other init's sub-threads exit? Thanks, Oleg.