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 8CB4EC43441 for ; Wed, 14 Nov 2018 14:37:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5D4BC21582 for ; Wed, 14 Nov 2018 14:37:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5D4BC21582 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733024AbeKOAkk (ORCPT ); Wed, 14 Nov 2018 19:40:40 -0500 Received: from mx1.redhat.com ([209.132.183.28]:35164 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727822AbeKOAkk (ORCPT ); Wed, 14 Nov 2018 19:40:40 -0500 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id F38988E59F; Wed, 14 Nov 2018 14:37:10 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.31]) by smtp.corp.redhat.com (Postfix) with SMTP id 098A95D75C; Wed, 14 Nov 2018 14:37:06 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Wed, 14 Nov 2018 15:37:10 +0100 (CET) Date: Wed, 14 Nov 2018 15:37:06 +0100 From: Oleg Nesterov To: Michal Hocko Cc: Chanho Min , "'Rafael J. Wysocki'" , 'Pavel Machek' , 'Len Brown' , 'Andrew Morton' , "'Eric W. Biederman'" , 'Christian Brauner' , 'Anna-Maria Gleixner' , 'Alexander Viro' , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, 'Seungho Park' , 'Inkyu Hwang' , 'Donghwan Jung' , 'Jongsung Kim' Subject: Re: [PATCH v2] exec: make de_thread() freezable Message-ID: <20181114143705.GB13885@redhat.com> References: <1541994885-20059-1-git-send-email-chanho.min@lge.com> <20181113145339.GD16182@dhcp22.suse.cz> <20181113161858.GE30990@redhat.com> <20181113180058.GT15120@dhcp22.suse.cz> <014a01d47c03$6b64eef0$422eccd0$@lge.com> <20181114103014.GN23419@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181114103014.GN23419@dhcp22.suse.cz> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Wed, 14 Nov 2018 14:37:11 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/14, Michal Hocko wrote: > > > I don't understand why it isn't appropriate for exec to block. The > > exec can freeze. When tasks are thawed, the killed sub-thread will die > > and wake de_thread(). The exec will continue to work from resume. > > Because this is fragile. I don't really agree, but... > I haven't checked the full set of resources the > task holds when in this path but I can imagine we can introduce lock > dependency on freezing really easily. And you are right, see another email I sent you a minute ago. But again, we need to change de_thread to sleep without cred_guard_mutex anyway, so I think this change is fine. At least in that it can't add the new problems. Oleg.