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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 42A50ECE566 for ; Fri, 21 Sep 2018 13:11:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E319021523 for ; Fri, 21 Sep 2018 13:11:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E319021523 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 S2389774AbeIUS75 (ORCPT ); Fri, 21 Sep 2018 14:59:57 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41016 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727392AbeIUS75 (ORCPT ); Fri, 21 Sep 2018 14:59:57 -0400 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.24]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 79DA55F74A; Fri, 21 Sep 2018 13:11:08 +0000 (UTC) Received: from vitty.brq.redhat.com.redhat.com (unknown [10.43.2.155]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 608C1308BDB2; Fri, 21 Sep 2018 13:11:02 +0000 (UTC) From: Vitaly Kuznetsov To: Oleg Nesterov Cc: "Rafael J. Wysocki" , "Rafael J. Wysocki" , Linux Kernel Mailing List , Linux PM , Andrew Morton , Dmitry Vyukov , Paul McKenney Subject: Re: [PATCH] kernel/hung_task.c: disable on suspend References: <20180913160851.18169-1-vkuznets@redhat.com> <4793718.OcKebjM5bH@aspire.rjw.lan> <87d0tg88l3.fsf@vitty.brq.redhat.com> <20180914162103.GA11171@redhat.com> <20180917165518.GA25931@redhat.com> Date: Fri, 21 Sep 2018 15:11:00 +0200 In-Reply-To: <20180917165518.GA25931@redhat.com> (Oleg Nesterov's message of "Mon, 17 Sep 2018 18:55:18 +0200") Message-ID: <87d0t70zdn.fsf@vitty.brq.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.84 on 10.5.11.24 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Fri, 21 Sep 2018 13:11:08 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Oleg Nesterov writes: > On 09/17, Rafael J. Wysocki wrote: >> >> On Fri, Sep 14, 2018 at 6:21 PM Oleg Nesterov wrote: >> > >> > > > Since you are adding the notifier anyway, what about designing it to make >> > > > the thread wait on _PREPARE until the notifier kicks it again on exit >> > > > fron suspend/hibernation? >> > >> > Well. I agree that freezable kthreads are not nice, but it seems you are >> > going to add another questionable interface ;) >> >> Why would it be questionable? >> >> The watchdog needs to be disarmed somehow before tasks are frozen and >> re-armed after they have been thawed or it may report false-positives >> on the way out. PM notifiers can be used for that. > > Or watchdog() can simply use set_freezable/freezing interface we already > have, without additional complications. > > Yes, this is not "before tasks are frozen", but probably should work? > > OK, I won't argue. I was hoping you and Rafael will come to an agreement but the discussion just died ... so where do we stand on this? I see the following options: 1) The v1 patch is good, no freezing/disabling/parking required. 2) Make the kthread freezable (btw, I tested your patch and it seems to work). 3) kthread_stop/kthread_run() (as you said 'no parking'). 4) Drop the patch and wait for the root cause (increasing jiffies) to dissolve. 5) ??? Ideas? -- Vitaly