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 B248CFC6182 for ; Fri, 14 Sep 2018 11:28:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7306E20861 for ; Fri, 14 Sep 2018 11:28:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7306E20861 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=rjwysocki.net 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 S1728192AbeINQnA (ORCPT ); Fri, 14 Sep 2018 12:43:00 -0400 Received: from cloudserver094114.home.pl ([79.96.170.134]:55260 "EHLO cloudserver094114.home.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726872AbeINQnA (ORCPT ); Fri, 14 Sep 2018 12:43:00 -0400 Received: from 79.184.255.178.ipv4.supernova.orange.pl (79.184.255.178) (HELO aspire.rjw.lan) by serwer1319399.home.pl (79.96.170.134) with SMTP (IdeaSmtpServer 0.83.148) id 787738763d39df73; Fri, 14 Sep 2018 13:28:53 +0200 From: "Rafael J. Wysocki" To: Vitaly Kuznetsov Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Andrew Morton , Dmitry Vyukov , "Paul E. McKenney" , Oleg Nesterov Subject: Re: [PATCH] kernel/hung_task.c: disable on suspend Date: Fri, 14 Sep 2018 13:26:13 +0200 Message-ID: <4793718.OcKebjM5bH@aspire.rjw.lan> In-Reply-To: <20180913160851.18169-1-vkuznets@redhat.com> References: <20180913160851.18169-1-vkuznets@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday, September 13, 2018 6:08:51 PM CEST Vitaly Kuznetsov wrote: > It is possible to observe hung_task complaints when system goes to > suspend-to-idle state: > > PM: Syncing filesystems ... done. > Freezing user space processes ... (elapsed 0.001 seconds) done. > OOM killer disabled. > Freezing remaining freezable tasks ... (elapsed 0.002 seconds) done. > sd 0:0:0:0: [sda] Synchronizing SCSI cache > INFO: task bash:1569 blocked for more than 120 seconds. > Not tainted 4.19.0-rc3_+ #687 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > bash D 0 1569 604 0x00000000 > Call Trace: > ? __schedule+0x1fe/0x7e0 > schedule+0x28/0x80 > suspend_devices_and_enter+0x4ac/0x750 > pm_suspend+0x2c0/0x310 > > Register a PM notifier to disable the detector on suspend and re-enable > back on wakeup. > > Signed-off-by: Vitaly Kuznetsov > --- > Changes since RFC: > - Add PM_HIBERNATION_PREPARE/PM_POST_HIBERNATION for consistency > [Rafael J. Wysocki] > --- > kernel/hung_task.c | 28 +++++++++++++++++++++++++++- > 1 file changed, 27 insertions(+), 1 deletion(-) > > diff --git a/kernel/hung_task.c b/kernel/hung_task.c > index b9132d1269ef..41955c5d8427 100644 > --- a/kernel/hung_task.c > +++ b/kernel/hung_task.c > @@ -15,6 +15,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -242,6 +243,26 @@ void reset_hung_task_detector(void) > } > EXPORT_SYMBOL_GPL(reset_hung_task_detector); > > +static bool hung_detector_suspended; > + > +static int hungtask_pm_notify(struct notifier_block *self, > + unsigned long action, void *hcpu) > +{ > + switch (action) { > + case PM_SUSPEND_PREPARE: > + case PM_HIBERNATION_PREPARE: > + hung_detector_suspended = true; > + break; > + case PM_POST_SUSPEND: > + case PM_POST_HIBERNATION: > + hung_detector_suspended = false; > + break; > + default: > + break; > + } > + return NOTIFY_OK; > +} > + > /* > * kthread which checks for tasks stuck in D state > */ > @@ -261,7 +282,8 @@ static int watchdog(void *dummy) > interval = min_t(unsigned long, interval, timeout); > t = hung_timeout_jiffies(hung_last_checked, interval); 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? > if (t <= 0) { > - if (!atomic_xchg(&reset_hung_task, 0)) > + if (!atomic_xchg(&reset_hung_task, 0) && > + !hung_detector_suspended) > check_hung_uninterruptible_tasks(timeout); > hung_last_checked = jiffies; > continue; > @@ -275,6 +297,10 @@ static int watchdog(void *dummy) > static int __init hung_task_init(void) > { > atomic_notifier_chain_register(&panic_notifier_list, &panic_block); > + > + /* Disable hung task detector on suspend */ > + pm_notifier(hungtask_pm_notify, 0); > + > watchdog_task = kthread_run(watchdog, NULL, "khungtaskd"); > > return 0; >